3.1. Cultivation of Jackfruits with Impact to its Nutrients
Due to more demand for waste mitigation and also extraction of valuable products with bioactive properties, there is more jackfruit cultivation reported all over India with some other countries such as Burma and Malaysia with some locations in Brazil. It is now one of the remunerative and also more valuable fruits in India. This jackfruit tree belongs to the Moraceae family and is also native tree of India [
14]. This plant is now cultivated throughout the tropical low land at both hemispheres. This jackfruit plant is widely grown in Western Ghats of India but its plantation is found in Bihar, West Bengal, Uttar Pradesh, Kerala, Tamil Nadu, Assam and Orissa. Some reports claimed its regular plantation in the U.P., especially marginal orchards. But in other parts this plant cultivation is reported as rare in plantations but jackfruit cultivation is found throughout South India up to an elevation of 2400 meters [
15]. Some reports have discussed the jackfruit plantation in systematic and proper ways and this plant growth needs rich and well drained sandy loam soils. For this plant plantation, soil drainage showed more importance with proper evidence. Sudden decline of numerous jackfruit plants in areas that are suffering a sudden rise of water level [
14,
15]. Reports on jackfruit tolerance capacity especially for moisture stress was shown and it can be shown to some extent of tolerance due to presence of lime and chlorine Areas near the river beds can be found to be ideally suitable for jackfruit plants cultivation. Further information on jackfruit plantation is a warm humid plain and it is able to flourish in humid hill slopes up to an elevation of 1500 meters. Jackfruit can deteriorate at higher altitudes with satisfactory plantations in arid and warm plains of South India [
16].
This jackfruit can provide unlimited scope for clone selection of promising strain/ species for multiple applications. Many types of these plants are available under various local names and it can be originated via clone selection. Gulabi, Champa, Hazarix are some examples of jackfruits. It needs storage conditions for jackfruit plantation. The impact to thick peels is found with good storage quality [
17]. Jackfruits can be easily gone for cross pollination and then its seeds can be found to easily propagate. To date, the prevailing population of jackfruits is distributed across numerous trees, exhibiting variations in their morphological characteristics such as shape, size, and density of tubercles, as well as differences in rind color, bulb size, fiber content, and fruit quality and maturity [
15,
17]. The storage longevity of jackfruit has been determined to be approximately 6 weeks when exposed to temperatures ranging from 0.1 to 12.7
0 C, provided that the humidity level is maintained at eighty to ninety per cent. The initial quality and maturity stage at the time of harvest are crucial factors that can significantly impact the storage life of a product. The jackfruit's storage life can be extended, allowing for transportation to remote locations for marketing purposes, through the utilization of appropriate packaging and wrapping techniques [
16,
17].
Reports for jackfruit application in India are found as culinary and also table fruits. And jackfruit used for culinary purposes is mainly found in more states in India. In market demand, tender fruits in spring and also summer are used as population vegetables. People have enjoyed jackfruits with high demand and premier cost/ price and sometimes this jackfruit cost/ price can be reached at a high rate in the year [
18]. Most people in the world used jackfruits in ripe form as tasty fruits with high sweet and also high nutritive values. In ripe form, jackfruits are good sources of vitamins A and C with some people believe in aiding in digestion process as ailments on a regular basis [
17,
18].
3.2. Compositions of Jackfruits Wastes
The waste produced from mature jackfruit fruits has been found to possess greater palatability compared to the waste generated from raw fruits. This waste material is composed of crude fiber, crude protein, and various minerals. It is also a significant source of energy, with a substantial quantity of NFE. The generation of rind from ripe fruit can serve as a source of nourishment for cattle [
19]. Additional applications of jackfruit-derived fruits have been documented for the production of pickles, dehydrated leather, and thin papad, as well as for canning purposes. These fruits have also been utilized in conjunction with soft drinks such as nectar and squash. In certain literature, rind has been identified as a viable source of protein. Additionally, it has been reported that extracts derived from rind waste can be utilized in the fabrication of jelly [
20]. Discussion of skin parts of fruits of jackfruit is reported for excellent cattle feed. Jackfruit plant/timber can be used for making furniture that can exhibit less chance of white ants infection/ attacks. Some efforts were done for latex extraction that contains resin. Latex from jackfruit bark can be used for making the plug hole in earthen vats and baskets and it has shown multiple applications for humankind [
19,
20].
Further, multiple reports are discussed for jackfruits parts (in terms of edible and non-edible parts) and non-edible parts are 70-80%, and out of this, outer rind, perianth, and central core of jackfruits is 60% under waste matters. A number of researches were done on biochemical composition by suitable analysis in jackfruits-based wastes with promising sources of health benefits. These bioactive compounds (i.e., valuable compounds/bioproducts) can be recovered/ generated by several microbial bioprocessing/extraction techniques in an eco-friendly way [
21]. The peel of jackfruit is a rich source of cellulose, protein, starch, and pectin. The chemical composition of dried jackfruit seeds includes carbohydrates (76%), protein (18%), and lipids (2.1%). Numerous phytochemicals, isoflavones, lignin, and saponins, along with several essential nutrients, have been documented in the seeds of jackfruit waste [
22]. Subsequent discourse revealed noteworthy sources of vitamins such as thiamine and riboflavin. The processing of jackfruit generates solid waste, including jackfruit peels, seeds, as well as latex. These waste products have been identified as contributors to environmental damage [
22,
23]. Researchers have put some effort into jackfruit wastes and they used eco-friendly feedstock/ sources for bioproducts synthesis in sustainable ways and this waste matter has shown the best biochemical compositions, helping in renewable mode bio-based products development. Further research has been conducted on the utilization of jackfruit peels as a sustainable source for the recovery of commercial pectin, biofuels, and other valuable products [
24,
25]. And
Figure 1 shows several form of jackfruits wastes with nutrients.
Various types of Jackfruits Wastes
Wastes generation from various types of vegetable and fruits/cultivation processes are discussed and a fruit can generate usually 3.5 to 10 kg of waste by weight and some fruits can generate higher quantities of waste (up to 25 kg). In the case of jackfruit plants, the outer parts of the jackfruit shell are found to contain a conical apex, covered via a thick robbery wall. And its fruits matured conditions, a non-edible core can be found on a longitudinal axis, fused with the rags [
26]. This part is then fused to the fruit’s rind part. Next, other wastes of jackfruit are bulbs and this bulb is composed of pulp, surrounded by seeds and it is found between the rags. Seeds numbers in jackfruits are nearly 100 to 500 and it can be found in nearly 18 to 25% of the weight of jackfruits. The kernel of the seeds can constitute nearly 90 to 95% of their weight and then pulp can account for 30% and it can be found between 70 to 80% of jackfruits components as non-edible [
27]. In non-edible parts of fruits, outer rinds, perianth, and central core can consist of 60% of the total wastes of jackfruits as discarded parts. Jackfruit peels and its conical carpel apices are also important components of jackfruit wastes. Apart from this waste, jackfruit leaves can be also used for some medical benefits such as relieving fever, boils, wounds, and skin conditions [
26,
27]. And then young fruits of jackfruit can exhibit acrid and astringent properties and characteristics and it can work on removing the flatulence in human health. The jackfruit seeds can be found as rich sources of protein concentrations (5 to 6%). In each tree of jackfruit, nearly 100 to 200 fruits can be produced as it is a large and evergreen tree every year. Still time, very limited research was done on unutilized wastes of jackfruits and then peels and fiber found nearly 60% of whole fruits as the largest known edible fruits from any plants. The jackfruit pulp and seeds are known to contain various bioactive compounds in addition to waste nutrients. The availability of these compounds in the fruit of this plant can vary, as reported in a previous study [
28]. The cultivation of this plant species is feasible during the monsoon season in coastal areas. The fruit of this plant is considered a cost-effective source of sustenance and is widely accessible at a low market value. Subsequent investigations were conducted on underutilized segments of jackfruit, with a focus on mitigating the accumulation of biowaste to promote the eradication of pathogenic microorganisms in augmented agricultural yields [
29]. The nutritional and functional characteristics of jackfruit peels warrant further investigation for the purpose of extracting bioactive compounds that may be utilized in the pharmaceutical industry [
29,
30].
Figure 2 shows the different jackfruit wastes with its valorized products.
The outer layer of jackfruit is comprised of peel which exhibits a spiky pattern on its surface. The peel of jackfruit is considered non-edible and is regarded as a potential waste material. Normally this part of fruit is discarded and then recently it is used for fertilizer sources. These parts of jackfruit can be used to feed the cattle in villages. It is a good source of carbohydrate (up to 24%), protein (up to 9%) and fibers (17.3%) [
31]. Jackfruit peels are utilized as valuable raw materials for functional ingredients like steroid, triterpenoids, saponin and carbohydrates. In jackfruit peel, more quantities of polyphenols are reported and it is linked to peel proximity with extrinsic domains. Some abiotic stress parameters/ factors (such as daylight, ultraviolet radiation and climatic induction) can impact the synthesis of polyphenol on the complete part of jackfruit peel [
32]. Other bioactive compounds in antioxidants can aid the chemical reactions in the human body and then it helps to offset the damages, mediated by oxidation reactions. Pectin content in jackfruits is reported to contain 9 to 15% of dry weight and it can make it a valuable source of the polysaccharides [
31,
32]. Extraction of various compounds is also used in the textile, paper and biofuel sectors with rich sources of celluloses. This can provide the alternative options to commercialized celluloses in pharmaceutical industries [
33,
34].
3.3. Valorization Techniques for Zero-waste Generation
In current scenarios, a number of researches are going on the zero-waste generation concept and many strategies (i.e., various valorization routes) are applied to achieve it. This was achieved on bread waste (BW) as the model development. But, there are a number of challenges (i.e., technical processing steps), occurring in various kinds of food wastes like jackfruits waste also. Normally, any type of food wastes hydrolysis including the jackfruits wastes can be done by enzymatic hydrolysis with assisting of physical and chemical agent processes. These approaches can generate monomeric compounds like glucose/ others sugar [
35]. These sugars from jackfruit wastes can be utilized for cultivation of suitable microbial systems with capability to use as carbon substrates and also efficiency to metabolite into fuels sources like ethanol/ butanol/ other bioproducts. One example is shown for BW valorization strategy with uses of
Euglena gracilis algae cultivation medium with systematic evaluation [
36].
This algal cultivation was found to future perspectives and also economic viability for biodiesel sources production. In context to valuable products except biodiesel, other targeted compounds like paramylon (β-1, 3-glucan) were synthesized from
E. gracilis with high productivity of 1.93 g.L
-1d
-1 and this productivity was 24% higher than control strains. In this product synthesis, people have applied the approaches of zero-waste disposal and then bread waste residues (BWR) was hydrolysed by enzymatic hydrolysis process and later it was valorized into syngas [
35,
36]. It was offered by a greener pyrolysis process for BWR and carbon dioxide was used as raw material for valuable products synthesis. CO
2-assisted valorization is an attractive technique not only towards efficient waste disposal, but in attaining to climate neutral or zero carbon emission. In reports, several types of agricultural wastes (licluding jackfruit wastes) are found to utilize as potential raw materials for the generation of valuable products like biofuels, biochar or also biopesticides with briquettes or others. Then biochar can be mixed with the soils and it can produce the carbon rich soils via contribution in carbon dioxides sequestration and soil fertility. So, jackfruit wastes can be anaerobically utilized for production of biogas, briquettes and also biochars that can improve the crop production [
37]. And other bioprocess, jackfruit waste can be gone for anaerobic decomposition into biogas and also for briquette production. But at high temperature, these waste (jackfruit waste) can decompose to produce biochar and then it can apply into the soil. This is good approach for carbon dioxide sink with helping in mitigation of effect of climatic change. It can find for anaerobic digestion process for jackfruit waste utilization for biogas production. This process has shown the economic viability for bioproducts generation [
36,
37].
Researchers have applied a mechanistic functionality process for carbon dioxide (CO
2) with systematic description. In this process, CO
2 was reacted with volatile matter (VMs) that evolved from BWR and it has helped to reduce the concentration of carbon dioxide. And it was done with proceeding to oxidation of VMs. Further process (like consecutive gas-phase-reaction ~GPR) was done with exhibiting a critical role in enhanced CO formation [
38].
Research endeavors were undertaken to identify the induction of gas-phase reactions (GPR) through the utilization of carbon dioxide (CO
2). A five per cent by weight (wt%) nickel/silicon dioxide (Ni/SiO
2) catalyst was employed for the purpose of studying the reaction kinetics involved in the process of mitigating CO
2. During the aforementioned procedure, the gaseous pyrolytic products, namely H
2 and CO
2, were acquired in terms of molar concentration [
39]. The catalytic pyrolysis process (Ni/SiO
2) in the CO
2 environment has resulted in a greater quantity of syngas, which is 2 and 6 times higher, correspondingly, compared to pyrolysis without the catalyst in the N
2 environment [
35,
40]. This study explores various valorization techniques that can be applied to the green extraction process. The aim is to develop innovative delivery systems, such as nano-emulsions, for bioactive compounds derived from fruit and vegetable waste, including jackfruit waste.. And
Figure 3 shows the complete jackfruit plants with edible and non-edible parts that later utilized as wastes and then converted into value-added products with zero-waste generation.
3.4. Advanced/ Green Extraction Techniques for Bioactive Recovery
In the valorization processes, researchers have applied various types of novel extraction techniques such as enzyme-assisted, microwave-assisted, ultrasound-assisted, high-hydrostatic pressure-assisted, pulsed-electrical field, and super-critical fluid extraction methods to derive various bioactive compounds that are used by food, pharmaceutical, cosmetic, and health-care industries [
32,
34]. These non-conventional green extraction techniques have the potential to zero waste, and thereby helping in sustainable energy conservation. The recent researches have also shown that various biofuels can be produced through microbial fermentation. Some examples of biofuels (like bioethanol up to 11-13%; biogas including methane via A.D process) with help of
Saccharomyces cerevisivae are produced through microbial fermentation [
41,
42] . Similarly, microbial fermentation has been effectively demonstrated to yield other valuable products like bioactive compounds and other products [
43]. Researchers have done sincere efforts in developing novel and efficient techniques that can recover the bioactive active compounds without any solvent contamination. Enzyme-assisted and pressurized liquid-assisted extraction are explored for jackfruit wastes applicable to other wastes that can recover the valuable products [
44]. Microwave-assisted and ultraviolet-assisted extraction techniques have been employed to derive the pectin polysaccharides and antioxidant phenolics respectively [
45,
46,
47],. Pulsed electric field-assisted and supercritical fluid-assisted techniques are also exploited for various natures of wastes valorization tasks that have recovered the bioactive compounds at high yield/ concentration [
48]. Among the various green modes of extraction techniques, their effectiveness can be varied with properties of the source matrix, its chemical structures and also process parameters/ factors (solvent, pressure, time or temperature [
43,
48].
Novel technologies can provide alternatives to conventional techniques of extraction of bioactive waste from various food wastes and these techniques are known to use water as solvent rather than organic chemicals. These techniques showed the positive impacts for phytochemicals, scattering inside the cytoplasm [
49]. Normally, hydrogen or hydrophobic bonds presence in the polysaccharide-lignin network/ complex can be found to be big challenges due to exhibiting difficulty in extraction of bioactive compounds [
50]. So these green techniques can be found to have a sustainable and eco-friendly nature with capability to achieve higher yield of the products compared to conventional ones. And these techniques have received more attention in the last few years due to more advantages [
49,
50]. Some techniques in context to green/ non-conventional mechanisms are discussed below.
In the enzyme-assisted extraction (EAE) process, enzyme concentration, compositions, particle size, water to solid ratio and also hydrolysis time plays an important role and it can influence the yield / concentration of bioactive compounds. Some compounds like carotenoid extraction (from pumpkin waste), anthocyanin from (
Crocus sativus/ grape fruit waste) were done via the EIE process [
51,
52]. Some bioactive compounds like phenolics (18-20 mg/g) were extracted from grape mare seed wastes with help of pectinase enzyme activity [
53]. Other efforts were done for antioxidant phenol extraction from apple pomace by using the commercial enzyme Pectinex Ò® and then phenolics recovery (p to 87%) from grape residues using Celluclast Ò®. EAE based technique is very effective to enhance the recovery of enzymes like pectinase, cellulases and pectinases from jackfruit wastes [
53,
54].
The second extraction method is known as ultrasonic-assisted extraction (UAE), and it has a number of uses and benefits including a larger yield, desired quality, and a straightforward procedure with minimal impact on the environment. The UAE approach uses the ideal frequency range (20-2000 kHz) and is well renowned for being both straightforward and inexpensive. It can be effective at two different facts, such as diffusion over the cell wall and washing the contents following cell disintegration [
55]. Due to wave creation of matrix expansion and compression, the UAE operating mechanism causes/generates cavitation phenomenon. The desired compounds are then extracted by causing the cell membrane to become permeable [
56]. The researchers investigated the many processes of the UAE process, including the acceleration of mass transfer, the disintegration of the particles, and the improvement of solvent accessibility. For this technique, samples of liquid-liquid or liquid-solid processing are frequently employed. Pressure, temperature, frequency, and sonication duration are other parameters that might affect the UAE process [
55,
56]. Recent research on the UAE revealed the widespread use of this procedure and shown its effects on yield and compound characteristics. Some excellent instances of UAE frequency have been documented for energy at or above 20 kHz, which changes the physical-chemical characteristics of phytochemicals by causing the production of free radicals [
57].
Figure 4 established the sophisticated processing methodologies employed for the extraction of bioactive compounds.
Some efforts on tannin extraction from Avaram shell is reported by application of UAE technique and it uses 100 W power. UAE based process has shown its impact in improved yield (160%) of tannins at 100W. This improvement in yield of tannin was explored and it was found due to improved mass transfer of cell components and a way of leaching of tannin by this power [
58]. Others bioactive compounds like good yield (caffeic acid~64.3 µg/g, ferulic acid~ 1513 µg/g and p-coumaric acid~ 140 µg/g) of phenolic acids by UAE technique are reported with better improvement compared to conventional techniques (maceration extraction) for same bioactive from same wastes [
59]. Temperature and prolonged time impact on UAE are found in the form of low yield of phenolic compounds from citrus peels. Some comparative studies were done on maceration and UAE technique performances in terms of consumed/ required time period for extraction of bioactive. And it was found to be a reduced time period (1h) for UAE technique compared to maceration assisted extraction (72h) for phenolic compounds from
Punica granatum fruits. Extraction of polysaccharides by UAE technique is found with good yield with proving of efficient technique [
57,
58,
59].
Another technique is pulse electric field-assisted extraction (PEF-AE) and its non-thermal process allowing direct current to produce. In this technique, application of high-voltage current/ pulse is passed through the materials that are kept/ placed between two electrodes for a short time period ( in range of microsecond to millisecond periods). These are based on the nature of products and also processing factors. During electric current passages through the suspension of cells, it can influence cell structures to be destroyed and then molecules can separate with respect to applied charge [
60]. This technique can function in a batch and also in continuous modes. For this technique performance, various factors like field strength, energy, pulse number, temperature and material properties can affect/ influence the yield of extraction and it can be worked based on designing a process for better performance. Application of PEF assisted extraction can be found in phenolic compounds and also anthocyanins extraction process from different wastes [
61]. PEF assisted extraction with maceration on grape skin can be applied for stability of compound during vinification and it can reduce the time of extraction. Some studies were done on untreated control samples along with PEF treated samples with maceration extraction process/ technique [
60,
61]. And it has shown improved color and also anthocyanin content/ yield with enhanced polyphenol contents in wastes like jackfruit. Further impact of PEF treatment can be found in the wind making process with reduced maceration time and also improved wine quality [
63,
64,
65,
66]. The cytomembrane in plant tissue's cell walls can influence the movement of intracellular material between cells. This approach for extracting bioactive substances is intriguing because it may trigger the cytomembrane in the tissue to disintegrate, which changes its permeable characteristics as well as increases mass transfer across the cells, leading to higher yields [
64,
65].
In context to advanced/ green extraction techniques, utilizes the electromagnetic radiation and it is transferred in the form of waves in the frequency range (300MHz- 300 GHz) with common uses of frequency of 2450MHz. This can be found to be equivalent to 600 to 700 W energy and this energy can be absorbed during the passage of microwave through suitable medium. This medium converts it into thermal energy via facilitating the processing [
66,
67]. Some bioactive compounds like flavonoids from
Terminalia bellerica plant were reported by using this technique and microwave in MAE technique can result in maximum yield (83%) and it is higher yield while compared to conventional techniques (flavonoid yield~64%). MAE technique is an endothermic and spontaneous process and it is also influenced by operating conditions like temperature and feed ratio on flavonoid yield. Same extraction was applied for hesperidin compound extraction with better yield (48%) from skin of citrus unshiu fruits [
68,
69]. During this technique extraction temperature showed high impact on bioactive compound yield and at 140oC, it showed decreased hesperidin quantity/ content due to the interference of the other solubilized substance. This compound influence has been found in inhibition of hesperidin crystal [
67,
69]. Other conditions on waste matter maturity level in case of peels, matured peels have yielded less hesperidin contents compared to immature peels (more than 3 times). Some impacts of power in MAE technique is reported and it was found for phenolic compounds extraction from chokeberries. Better yield of phenolic compounds (420.1 equivalent mg gallic acid/100g. chokeberries) is reported at 300W for 5 min [
70,
71]. Extraction of silibinin from
Silybum marianum waste with help of MAE technique is discussed with better yield (97.3%) and it is higher than conventional approaches. Similar study was done on this technique efficiency and it was reported for phenolic compounds from apple pomace wastes [
72]. This compound extraction yield from this technique is influenced by several factors/ parameters such as solubility, dielectric constant, dissipation factor (d) and solvent nature. The higher recovery of flavonoid by MAE (up to 74%) is reported and it is better than traditional recovery / extraction process (up to 70.5%) with proof of efficient process [
73,
74].
During the supercritical fluid extraction process (SC-FE), desired compound extraction is carried out by using the solvent above the critical point (CP) and this CP can be found as a specific temperature (Tc) or pressure (Pc) point. But as above to CP, gas and liquid cannot exist as separate phases [
75]. At CP, fluids/ solvents can exhibit the liquid (in terms of density) and salvation power/ gas (viscosity, diffusion and surface tension). These properties can facilitate the higher yield of bioactive compounds within a short time. In case of supercritical fluid extraction (SFE), there is a need for a good mobile tank (consisting of CO
2 pump), solvent vessel, oven, controller and also a trapping vessel [
75,
76]. Now most of bioactive extraction is done by application of green technologies compared to conventional methods and in this context, supercritical CO
2 extraction is discussed with better yield of naringin from citrus paradise. This approach uses the ethanol as a modifier (14% by wt.) at same process conditions like 58.6
oC temperature and 9.5 MPa pressure [
77].
This technique is applied for phenolic compound extraction from rice wine lees wastes with uses of Soxhlet extraction (SE) and SFE. Then it was compared for yield of bioactive compounds with reduced extraction (1 h compared to 6 h in case of traditional extraction technique) using the less ethanol needed with better yield of phenols (43%) [
78]. In the process of SFE, carbon dioxide is a common solvent, used in food sector tasks and it is safe with easily attainable critical conditions (at 30.9 and 73.8 bar) for food processing. Some major limitations such as low polarity are disclosed but it can be improved by using polar solvents like methanol. Ethanol, dichloromethane and acetone) [
77,
78]. These can work as modifiers with capability to improve its solvating power and also enhance its extraction efficiency with minimum/ no interaction between analytes and matrices. Some parameters like low diffusibility of the solvent into matrix, extended extraction time, high-pressure requirement and expensive infrastructures can also be found some challenges for this technique [
76,
78]. Further, consistency and reproducibility during the continuous process can be found as some more limitation of this extraction technique and these can stop scalability of this technique [
77,
79].
3.5. Microbial Fermentation for Jackfruits Waste Conversion
For better utilization of jackfruits wastes, it needs several types of effective pretreatment process and it can be applied as physical, chemical and biological processes to hydrolyse its complex organic matter. These strategies help in valorization of jackfruits wastes into value-added products including fuels (bioethanol or biogas,)/ other bioproducts (bioplastic, feeds, or functional food additives) [
80]. From jackfruit wastes, nowadays, bioenergy production and promotion is also carried out by several researchers groups and it can utilize the jackfruit waste as renewable resources and it is also an eco-friendly and cost-effective process to generate the alternative fuels options against fossil fuel [
81]. In recent years, efficient bioconversion of jackfruit wastes into several types of fuel sources is done with the help of microbial fermentation process by using different microbes such as bacteria, yeast, fungi [
74,
75]. Yeast (like
Saccharomyces cerevisivae for ethanol), bacteria (for methane, methanogen like
Methanosarcina barkeri and
Methanococcus maripaludis) and fungi (like
Rhizopus oryzae MNT 006,
Aspergillus oryzae MNT for ethanol) is reported for biofuel production [
16,
37,
82]. And these efforts can help in reduction of environmental pollution and also help in bioremediation processes (i.e., several toxic dye removal) in water sources/ aquatic environments that were contaminated with dye color. Some review papers have addressed the color dye removal from water bodies with help of jackfruit waste uses with finding of utilization feasibility. This effort can solve the several serious ecological problems in jackfruit producing nations [
81,
83].
Several reports claim a waste generation quantity of jackfruit in the range of 5 to 7 kg wt. per fruit and this waste showed its potential for conversion into a wide range of bio-products such as biofuels, animal feeds or bioactive components and these are used in bakery and packaging material industries. In case of wastes (including jackfruit wastes also) materials hydrolysis, physical, chemical and biological pretreatments processes are applied and it helps in conversion into simple sugars and also in final production synthesis under effort of valorization [
84]. Utilization of jackfruit wastes can result in several fuels products synthesis / production. These can be achieved by application of pretreatment and extraction steps via valorization of waste biomasses in an effective and successful manner. In recent years, numbers of vaporization technologies have developed for jackfruits waste hydrolysis and later these helped to conversion of desired products via utilization of several bioprocesses / green extraction steps and it can promote sustainable products utilization in the biorefinery and also the bioeconomic of the world [
85]. Normally jackfruit is reported to contain 0- 80% non-edible parts and out of this quantity, 60% of jackfruit wastes is outer rind, perianth and central cores parts. Number of analyses for biochemical composition for jackfruit waste were done with utilization of these wastes with recovery of health benefits products [
84,
85]. The peels of jackfruits waste are good sources of protein, cellulose and pectin and then seed waste is good sources of carbohydrate (76%), protein (18%) and lipid content (2%). In context to bioenergy production from jackfruit wastes utilization, several types of pretreatment are applied as crucial steps with conversion capacity into complex forms of organic matter into simpler ones. Pretreatment step in the complex organic matter conversion process helps in enzymatic reactions of hydrolysis during the saccharification processes and this step can ensure the simple sugars form for fermentation via the help of different microbial agents [
86]. Good example of jackfruit wastes conversion is found for ethanol production/ extraction process. This process utilizes the low-pressure and also high-intensity ultrasound processes that affect compositions and functionality of isolated proteins from jackfruit seeds [
80]. Jackfruit waste is gone for several processing tasks by a variety of physical methods to develop the valuable products and some of these are irradiation, microwave processing, supercritical fluid and high pressure processing extraction as common and advanced processing methods [
86,
87].
In effort to hydrolysis of jackfruit wastes, several approaches/ methods of chemical treatment are applied in acidic or alkaline solution (low to high concentration) at temperature of 130
oC and 210
oC via mixing the waste matter. During the chemical agent assisted pretreatment process, waste matter is gone for a few minutes to few hours to get fermentable sugars and it can be dependent on pretreatment conditions [
88,
89]. Researchers have applied these processes for methane production, energy potential and also environmental benefits using jackfruit peels. The effect of methane generation via pretreatment of jackfruit wastes with 5% alkaline hydrogen peroxide (AHP) and it has shown its influence in production of enhanced methane yield and also biodegradability (up to 70%) while compared to untreated waste matter [
90]. Some studies were done on analysis of potential of annual energy production from jackfruits, treated with 5% AHP solution. Alkaline extraction techniques were applied for isolation of starch from jackfruit seed wastes and then it has 18% starch from seeds [
89,
90].
During the conventional chemical and physical pretreatment process, high investment of reagents, machinery and energy is needed and in those treatment processes, it is needed before biological pretreatments. These can be applied for cellulosic and lignocellulosic matters for enzymatic saccharification processes [
91,
92]. During the biological treatment process, many living agents such as fungi/ bacteria are used and it utilizes less energy and is also an eco-friendly process. Many microbial agents are known to possess the cellulolytic and hemicellulolytics activities that can be utilized for jackfruits waste utilization task [
93]. Among several microbial systems,
Saccharomyces cerevisivae is applied for ethanol production from jackfruit wastes and ethanol contains the 35% oxygen contents and it can be utilized for burning process for production of lesser quantity of nitrogen and also particulate matters than the gasoline combustion process [
90,
93]. And
Figure 5 discussed the pretreatment approaches for hydrolysis and also bioenergy development.
3.7. Bioethanol
In context to value-added products recovery from jackfruit wastes, it has discussed bioethanol production from enzymatic hydrolysis and microbial fermentation of cellulosic biomass including jackfruit wastes and it is cost-effective and eco-friendly technique/ approach [
100]. In this fuel synthesis process, jackfruit wastes like peel material are utilized as potential feedstock and this waste matter contains high quantities of carbohydrates contents/ %. Numbers of studies were done for saccharifying jackfruit rind matter via application of recombinant enzyme endoglucanase from
Bacillus subtilis strain MUS1 microbes at temperature of 50
oC and pH 5.0 with 15 mg/ ml substrates ratio/ quantity 101]. This recombinant enzyme from
Bacillus subtilis can help in generation of more quantities of sugars during the saccharification process of jackfruits wastes [
41,
100]. From different types of wastes, bioethanol is produced as alternative energy sources. These wastes are good sources of natural products like carbohydrates and then it is utilized as potential feedstock for ethanol production with the hydrolysis and fermentation process. In this context, jackfruit seed is the best feedstock with rich sources of carbohydrates [
101]. Number of research studies are done on determination of pH effect on carbohydrates hydrolysis that can be utilized for bioethanol production. For hydrolysis of carbohydrates from jackfruit seed, effective pretreatment with a pH dependent process was done by application of a separate fermentation hydrolysis (SHF) process [
102].
This process has used the sulphuric acid solution as hydrolysing agents. Later, the fermentation process with help of
Saccharomyces cerevisiae strain was used in a fermentor vessel at different pH values (such as 2, 3 and 5) for 70h period. From this experiment results, it was claimed for optimum glucose content (75%) and pH (3.0) that supported the high concentration of bioethanol (58%) in fermentation broth [
101,
102,[101,102,]. From this research work, it has discussed the fermentation stage role and it was found that high concentration of glucose can push the high concentration of bioethanol with linear relationship [
103]. This published paper talked about the glucose concentration and high ethanol concentration from jackfruit seeds waste. This jackfruit seed showed the high potential for feedstock for bioethanol biosynthesis at cheap price [
101,
103].
Bioethanol production from fermenting raw matters like jackfruit waste is reported with the suitable microbial system. During the fermentation process, ethanol production jackfruit wastes is reported with application
Saccharomyces cerevisiae strain. This yeast strain showed high capability for ethanol production and it is due to natural adaptation properties and also high tolerating sugar/ ethanol/ chemical inhibitor [
104]. Ethanol can be synthesized by petroleum product/ by fermentation process. In the biological process, cellulose or hemicelluloses from jackfruit wastes is hydrolysed and then it is utilized for the ethanol production process. Most lignocellulosic biomass including jackfruit waste is rich sources of carbohydrates and then it needs the effective pretreatment process for fermentative sugars that can be used in ethanol production. Later, product separation and purification process is also needed to get the pure ethanol [
101,
104]. For this bioethanol production, jackfruit peels were selected as potential substrates and then enzyme/ microbial system (Saccharomyces cerevisiae) was used for getting the fermentative sugars and ethanol. Now, ethanol can be present in alcoholic drinks with more uses of this yeast in the bakery industry and fermented food and alcoholic drink preparation/ production [
103,
104]. Some efforts were done on jackfruit straw waste and then it was processed with fermentation as starter substrates. From this process, bioethanol was separated by a distillation process. Starter mass and fermentation time was checked to achieve the maximum ethanol yield with utilization of yeast like
S. cerevisiae and urea as N- nutrients [
105].
At optimum yeast mass (40g) of
S. cerevisiae with distillate volume of 13.6 ml. It has been found after 96 h of fermentation rime, distillate / ethanol yield was 15.2 ml. But at optimal condition of fermentation, volume of bioethanol distillate was found to be 30 ml with the distillation temperature at 70-80
oC. From this approach for ethanol production, its refractive index (1.354), density (0.367 g/ ml) and boiling points (71-72
oC) was reported [
106]. Another report, bioethanol production is discussed from utilization of Sri Lankan rotten fruits (without skin) including with jackfruits wastes. This ethanol was produced in a batch process with optimization of fermentation process parameters [
106,
106]. In optimization of fermentation process, some optimization techniques like Genetic algorithm (GA), Response Surface Methodology (RSM) and also Particle Swarm optimization (PSO) were discussed. During the bioethanol production, different overripe fruits were taken and these fruits were jackfruit, papaya and banana with uses of two microbes at three fermentation conditions. During these experiments, maximum ethanol yield with RSM (13.4 vol. %), GA (13.4 vol. %) and PSO (13. 36 vol. %) by the use of banana variety fruit fermentation and
Pseudomonas mendocina microbial strain (ratio~ 1:1), pH (5.1) and temperature (35
oC) [
107,
108].
3.8. Biogas
Biogas generation from different types of jackfruit wastes is a good effort for sustainable fuels sources. In this context, potential of biogas production is found from different fruit wastes like banana peels, jackfruit wastes, and pineapple wastes and these were gone for co-digestion process with cow drug and then this effort helped to provide alternative energy sources [
109]. During these experiments, substrates from each fruit waste were sent to the co-digestion process with varying ratios (0%, 25%, and 50%) of cow dung. These were done in laboratory scale anaerobic digesters (up to capacity of 250 ml) and then it was run for 30 days to generate or produce the biogas from jackfruit (82.3 ml), banana fruit (189 ml) and also pineapple fruit waste/ peel (262 ml) is found [
110]. In another experiment of this study, jackfruit waste, pineapple waste and banana peels were co-digested with 25% of cow dung and then biogas production from these fruits was increased by two to three times [
110,
111].
And 50% of cow dung with these fruits waste has improved the biogas yield by two folds. From these reported results, a mixture of jackfruit, banana peel and pineapple peel can be found much better in biogas production yield and it can help in the energy supply chain process for our daily needs [
111]. During the biogas generation experiment, some efforts were done on experimental design, digester set-up, and volume and biogas composition determination that was produced from jackfruit waste, banana and pineapple peels with cow dung. And biochemical methane potential (BMP) assay protocol was applied for anaerobic digestion process [
112]. Evaluation process for biogas quality attributes was done for process that used the from jackfruit waste, banana and pineapple peels with cow dung with batch digestion process. In this experiment, an anaerobic system was found to be 500 ml capacity and it was submerged in a 20 litre temperature regulating water bath and a 250 ml measuring cylinder for the generated biogas measurement task via displacement method. Temperature of the water bath was maintained at 36.5
oC [
109,
112].
In context to value added products recovery, utilization of jackfruits was reported and it discussed the production of biogas, biochar and briquettes from jackfruit waste. In many developing countries, huge potential is found due to more quantity of organic waste accumulation and then it can be utilized for conversion into many types of fuel sources like biogas generation [
37]. Waste organic matters in rural areas due to small holder farmers can be generated and then these can be utilized for different nature of biofuel sources. In context, biomass wastes like jackfruit waste can be managed to produce the bioenergy with mitigation in GHGs (greenhouse gasses) emission quantity via a well-managed way [
113]. Now, decomposing of organic matter can be minimized via generation of biogas. Due to more quantities of agricultural waste like jackfruit waste can be utilized as cheap raw materials for production of bioproducts like biofuels, biochar and biopesticide with briquettes and others [
114]. Biochar production from waste matter is good effort and then biochar can be mixed with the soils and it can help to produce soils rich in carbon with contribution in carbon dioxide sequestration and soil fertility [
115]. Some papers have focussed on jackfruit waste utilization for biogas production from anaerobic digestion process with biochar and briquettes production. From the anaerobic process for jackfruit wastes utilization, biogas can be produced [
110]. It needs a high temperature for jackfruit waste decomposition tasks to help in biochar production. This effort of research can help various products synthesize information with help in mitigation of climatic changes and also carbon dioxide sink in soil [
37,
115]. And
Figure 6 discusses the jackfruit wastes with different microbial / chemical transformation approaches for many products synthesis to support the zero-waste generation.
3.10. Bioactive Compounds
Pectin used in the food sector and pharmaceutical / cosmetics sectors is reported to serve as various agents like emulsifiers, binders and stabilizers) with performing various functions [
33]. Polysaccharides sources in jackfruit peels can help in human diet and then it can maintain good immunity activity with some protective functions like cancer, blood sugar, ulcer, and bad cholesterol [
34]. In pharmaceutical industries, pectin is utilized as bonding agents for various formulations of pills and also multi-purposes delivery. In food sectors, use of jackfruit peels is used in papers, paints, optics and also environmental remediation with biofuel sectors. In case of phenolic compound yield from orange peel, improvement in yield (15%) was achieved by PEF at power of 7KV/cm 62].
Reports on greater yield of phenolic compounds (102.9 mg GAE/100g food waste) and flavonoid compounds (37.6% QE/100g FW) from various wastes, such as onion waste, are described in this approach, with superior yield improvement (2.2 and 2.7 times, respectively) compared to control samples. The effects of electric field intensity and extraction duration on phenolic and flavonoids compound yields are demonstrated [
63]. Nowadays, efforts are being made in the food processing sector to produce nanoemulsions, which can be useful in the delivery system for various bioactive substances capable of performing various functions. These actions boost bioavailability, regulate ingredient discharge, alter product texture, as well as preserve the substance from degradation [
98]. In this technique, intensive research is going on to make it more effective in terms of a broad range of bioactive extraction from any type of wastes including jackfruit waste. For the nanoemulsion process, the delivery system can proceed for bioactive compounds with understanding of specific functions especially in food-based delivery systems and bioavailability in the human body. Some recent studies are done for understanding mechanisms on desirable bio-accessibility, metabolism and absorption of the encapsulated compounds and these can help in alteration in their properties in the gastro-intestinal tract [
99].
Further studies were done loading capacity of bioactive compounds that are encapsulated form like nanoemulsion, exhibiting the better release properties of bioactive compounds [
98,
99]. Cultivation of jackfruit plants in the world is good and potential sources of valuable biomaterials and wastes from jackfruit plants is a good source of carbohydrates, fats, protein and also phytochemicals [
97,
99]. In the case of bioactive compounds from wastes of fruits/ vegetable sources, it showed a positive impact on human health via contributing to modulation of the metabolic processes and also cellular activities [
94]. Some bioactive compounds showed their properties of antioxidants, anti-cancer, anti-inflammation and anti-allergenic. Some compounds contribute to anti-atherogenic activity and these properties of bioactive compounds can depend on the pathways and also their bioavailability in the human body. In categories of bioactive compounds, some are hydrophobic in nature and they showed less bioavailability in the human body [
95]. In this context, some efforts have been made on technological advancement such as nano-emulsions application. And this effort helped in enhancing their stability and functional properties. Bioactive substances can be obtained via traditional and non-traditional methods, each with its own set of benefits and drawbacks [
94,
95]. And
Table 2 shows the bioactive compounds with health benefits from jackfruit wastes.