Landfilling is one of the most widely used processes for the disposal of municipal solid waste (M... more Landfilling is one of the most widely used processes for the disposal of municipal solid waste (MSW). It is designed to dispose high quantities of waste at economical costs. Landfill management may pose serious environmental impacts through the discharge of highly polluted wastewater also known as leachate. The treatment of landfill leachates (LFL) is very complicated, expensive and requires various combined process applications due to their high COD and nitrogen levels.
Coffee processing byproducts are studied in this work for their valuable components. Spent coffee... more Coffee processing byproducts are studied in this work for their valuable components. Spent coffee grounds (SCG) and coffee silverskin (CSS) from Coffea arabica species were investigated for the determination of ethanol/water extracts bioactive molecules of interest. Phenolic compounds evaluation revealed that SCG enclose important amounts of polyphenols (8.425 mg GAE.g DW) and flavonoids (2.801 mg CE.g DW). Nevertheless, the highest levels of tannin (3.45 mg CE.g DW) were obtained with CSS. The total antioxidant activity of SCG was equal to 8.267 mg GAE.g DW, the DPPH test showed an IC50 value of 18 μg.ml -1 and the inhibition of β-carotene bleaching of IC50 was 600 μg.ml. While, the CSS showed better reducing power with an IC50 value of 120 μg.ml . Therefore, SCG proved to be more interesting than CSS regarding its antioxidant potentiality and its richness in phenolic compounds to be incorporated as food or therapeutic additive.
Cet ouvrage presente quelques alternatives de traitement et de valorisation des rejets des indust... more Cet ouvrage presente quelques alternatives de traitement et de valorisation des rejets des industries des boissons sucrees qui referment des teneurs en glucides assez importantes exploitables pour la production des microorganismes et des molecules a interet industriel. Les differents procedes proposent l’exploitation de ces produits comme matrice de production aussi bien de biomasse (ferments : bacteries, levures et moisissures) ou des molecules a usages divers (hydrogene, bioethanol, acides organiques, ...etc). L’utilisation de ces boissons comme milieux de culture permet d’epuiser les sucres initialement presents dans la matrice et aboutir par consequent, a un rejet industriel beaucoup moins polluant pour l’environnement. Ces substrats propres ouvrent des perspectives dans les poles de production des microorganismes et des molecules offrant aux marches de la fermentation, de la nutrition humaine et de la nutrition animale, des bacteries repondant aux normes de qualite y compris ce...
Kefir grains are a microbial consortium of different genera of bacteria and yeasts. In this study... more Kefir grains are a microbial consortium of different genera of bacteria and yeasts. In this study, the performance of Tunisian Kefir grains during the biological treatment of a mixture of Gouda cheese whey and white wastewaters (GCW) in ratio 1:1 with very high organic matter concentration is investigated. The biological process was evaluated and optimized through the response surface methodology. Under the optimum conditions, Kefir grains concentration of 1.02%, temperature at 36.68 °C, and incubation time of 5.14 days, the removal efficiencies of COD, PO 4 3− , and NO 3 − were 87, 37.48, and 39.5%, respectively. Interestingly, the reusability tests of the grains proved not only their high resistance to harsh environmental conditions but also their great potential for more practical applications. Particularly, different strains were isolated from the grains and identified as Kluyveromyces marxianus , Lactoccocus lactis , Lactobacillus kefiri , and Bacillus spp. using 16S rDNA sequence analysis and rep-PCR fingerprinting. At the biological level, the raw GCW (RGCW) has a negative impact on the Hordeum vulgare both on seed germination, and on the growth parameters of seedlings. Interestingly, after Kefir grains treatment, the treated GCW (TGCW) allow a seedlings growth and germination rate similar to those soaked in water.
In this study the biotreatability of Jebel Chakir landfill leachate (Tunisia) using a mixture of ... more In this study the biotreatability of Jebel Chakir landfill leachate (Tunisia) using a mixture of dairy industry reject (bactofugate) and Aloe sp. leaf gel was evaluated. The effect of Aloe gel fermentation using Saccharomyces cerevisiae yeast strain was investigated against some selected bacterial and fungal strains. The inoculation size effect of the treatment mixtures (2, 6, 10 and 12%) in the treatment efficiency was also studied. The obtained results showed that when natural Aloe gel and bactofugate mixtures were used the recorded chemical oxygen demand removal rates exceeded 56% within 48 h of treatment. Whereas, the use of the fermented Aloe gel in the treatment mixtures has promoted the organic matter removal to reach 72%.
The wastewater from the dumping site usually contains high pollutant levels. Biological process a... more The wastewater from the dumping site usually contains high pollutant levels. Biological process and physico-chemical treatments are among several technologies for wastewater treatment. Using microorganisms in the treatment of landfill leachate is an emerging research issue. Furthermore, bioremediation is a feasible approach for pollutants removal from landfill leachate which would provide an efficient way to resolve the issue of landfill leachate. In this study, the performance of yeast and bacteria isolated from kefir grains was assessed for landfill leachate treatment. Kefir grains microbial composition was evaluated by molecular approaches (Rep-PCR and 16S rRNA gene sequencing). The obtained outcomes denoted that high concentrations of lactic acid bacteria and yeast populations (over 107 CFU/mL) were found in the kefir grains and were essentially composed of Lactococcus lactis, Lactobaccillus kefirien, bacillus sp., Lactococcus lactis and Kluyveromyces marxianus. The co-culture with 1% of inoculum size was demonstrated as the most efficient in the degradation of different contaminants. The overall abatement rate of chemical oxygen demand (COD), ammonium nitrogen (NH4 + -N) and salinity were 75.8%, 85.9% and 75.13%, respectively. The bioremediation process resulted in up of 75% removal efficiency of Ni and Cd, and a 73.45, 68.53 and a 58.17% removal rates of Cu, Pb and Fe, respectively. The research findings indicate the performance of L. lactis and K. marxianus co-culture isolated from kefir grains for the bioremediation of LFL.
This research was carried for the coproduction of two industrial enzymes: α-amylase and protease ... more This research was carried for the coproduction of two industrial enzymes: α-amylase and protease via SSF by Rhizopus oryzae on humidified bread waste. Fermentation time, inoculum size, initial moisture content, salt solutions, and the thickness of the substrate were investigated one by one. Fungus culture was carried out in sterile aluminum trays, and pH was adjusted to 5.5. The main results showed that the highest levels of enzyme production were obtained at 120 h, 65% relative humidity, height media of 1 cm, 105 spore/g, and M-9 solution (g/L): NaH2PO4, 12.8; KH2PO4, 3; NaCl, 0.5; NH4Cl, 1; MgSO4 7H2O, 0.5; CaCl2 2H2O, 0.01. α-Amylase (100 U/g) and protease (2400 U/g) produced by SSF from Rhizopus oryzae (CH4) on BW as substrate are of great interest in industries and could be valorized as enhancers of the bread making process.
This study investigates the performance of the combination of biological pre-treatment with Kefir... more This study investigates the performance of the combination of biological pre-treatment with Kefir grains (KGs) and photocatalytic process using Ag-doped TiO2 nanoparticles (NPs) for the simultaneous removal of toxic pollutants from landfill leachate (LFL). After 5 days of 1% (w/v) KGs pre-treatment at 37 °C, TOC, COD, NH4+-N, and PO43- removal rates were 93, 83.33, 70 and 88.25%, respectively. The removal efficiencies were found to be 100, 94, 62.5, 53.16 and 47.52 % for Cd, Ni, Zn, Mn and Cu, respectively. The optimal conditions of Ag-doped TiO2 photocatalytic process were optimized using Box-Behnken design and response surface methodology (BBD-RSM) to enhance the quality of pre-treated LFL. Interestingly, Ag-doped TiO2 photocatalytic process increases the overall removal efficiencies to 98, 96, 85 and 93% of TOC, COD, NH4+-N, and PO43-, respectively. Furthermore, the removal efficiency of toxic heavy metals was gradually improved. In addition, KGs and Ag-doped TiO2 exhibited excellent recyclability showing the potential of combined biological/photocatalytic process to treat hazardous LFL.
Abstract In this work, the feasibility of baker yeast production using white bread waste is inves... more Abstract In this work, the feasibility of baker yeast production using white bread waste is investigated. Grinded and sieved white baguette waste was hydrated and hydrolyzed differently using enzymes preparations to obtain two growth mediums. Medium (I) contained a mixture of alpha amylase and amyloglucosidase; and Medium (II) contained a mixture of alpha amylase, amyloglucosidase and protease enzymes. The clarified media were diluted and supplemented with NH4SO4 (3.5 g/l), and KH2PO4 (2 g/l). A commercial baker yeast strain was reactivated and a preculture was prepared for the mediums inoculation. Fermentation was carried out in Erlenmeyer flasks and incubated in the thermo-shaker (30 °C, 150 rpm). After 48 h of fermentation, important biomass production was recorded in Mediums (I) and (II) (1.04 × 108 CFU/ml and 2.74 × 108 CFU/ml) compared to the control medium (1.63 × 108 CFU/ml). Hence, the productivity ratio of Medium I and Medium II was estimated to be 0.63 and 1.68. Microbial growth, sugars and proteins consumption kinetics were studied. The obtained results indicated that the production of yeast biomass could be an attractive alternative for bread waste valorization ensuring a global biomass yield of 0.77 g/g.
Residuals are responsible for the polluting load increase of soft drink industry wastewater due t... more Residuals are responsible for the polluting load increase of soft drink industry wastewater due to their high sugar contents. The present work proposes an upstream segregation of residuals to be biologically treated by the bioconversion of their carbohydrates content into baker's yeast biomass. Carbonated soft drinks (CSD) and nectars and juices (NJ) ranges were considered. Different incorporation ratios of NJ in the CSD (0–75%) have been investigated for balanced growth medium. Despite the nitrogen deficiency of media, results showed that NJ incorporation promoted the microbial growth. Media containing more than 50% of NJ exhibited ∼25% sugar-biomass conversion rates. The chemical oxygen demand (COD) of the media exceeded 70% at the end of fermentation. Moreover, valuable components were recovered by yeast production. Nutrient consumption rates varied from 65.4% for sugar and calcium content to in excess of 99% for protein and other minerals. In order to investigate an availabl...
The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella ... more The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella sp.) cultivation was investigated in this study. Landfill leachate was collected from Borj Chakir landfill, Tunisia. A full factorial experimental design 22 was proposed to study the effects of the incubation time and leachate ratio factors on the organic matter removal expressed in chemical oxygen demand (COD) and ammoniacal nitrogen (NH4─N) and on the biological response of Chlorella sp. expressed by the cell density and chlorophyll content. All experiments were batch runs at ambient temperature (25 ± 2 °C). The Chlorella sp. biomass and chlorophyll a concentrations of 1.2 and 5.32 mg L−1, respectively, were obtained with 10% leachate spike ratio. The obtained results showed that up to 90% of the ammoniacal nitrogen in landfill leachate was removed in 10% leachate ratio spiked medium with a residual concentration of 40 mg L−1. The maximum COD removal rate reached 60% within 13 days of incubation time indicating that microalgae consortium was quite effective for treating landfill leachate organic contaminants. Furthermore, with the 10% leachate ratio spiked medium, the maximum lipid productivity was 4.74 mg L−1 d−1. The present study provides valuable information for potential adaptation of microalgae culture and its contribution for the treatment of Tunisian landfill leachate.
This work proposes a novel approach for the reuse and the recovery of dairy wastes valuable compo... more This work proposes a novel approach for the reuse and the recovery of dairy wastes valuable components. Thermal coagulation was performed for dairy effluents and the main responsible fraction for the organic matter content (protein and fat) was separated. Dairy curds were prepared for the formulation of bacterial growth media. Protein, sugar, fat and fatty acids contents have been assessed. Samples treated at 100 °C exhibited marked improvement in terms of protein (25-50%) recovery compared to those treated at 80 °C. Fatty acid analysis revealed the presence of unsaturated fatty acids (mainly oleic acid) that are essential to promote Lactobacillus growth. Previously isolated and identified bacterial strains from dairy wastes (Lactobacillus paracasei, Lactobacillus plantarum, Lactococcus lactis and Lactobacillus brevis) were investigated for their ability to grow on the formulated media. All the tested lactic acid bacteria exhibited greater bacterial growth on the formulated media su...
International Journal of Environmental Science and Technology
Among dairy effluents, bactofugate (B) and decreaming racking water (D) were identified as the mo... more Among dairy effluents, bactofugate (B) and decreaming racking water (D) were identified as the most polluting due to their organic load content expressed in the chemical oxygen demand (156–240 g·L−1). Joining the plant wastewater, such effluents contribute to the increase of the polluting load of the wastewater treatment plant input which disturbs the treatment performance. This work proposes an upstream segregation of those dairy effluents for combined physical–chemical and biological treatment. An experimental design was proposed to investigate initial pH, applied temperature and exposure time factor effects on the thermal coagulation process. The fermentation of the resulted supernatants using Lactobacillus lactis ssp. lactis was performed. The optimized thermal coagulation pretreatment was obtained at (pH; T(°C); t(min)): 6, 60 °C and 5 min, with both (B) and (D) effluents. Resulted clarified whey sugar, protein and fat contents were assessed. The physical–chemical treatment resulted in considerable organic matter removal: 45% for (B) samples and 31% for (D) samples of proteins content and almost the total fat content. However, there is no considerable effect on the sugar content reduction, which remains responsible for the major fraction of the whey residual chemical oxygen demand (COD). Clarified whey fermentation using Lactococcus lactis ssp. lactis strain induced important sugar consumption rates. Therefore, important sugar consumption rates were recorded and the COD removal efficiency was improved. The recorded global COD removal efficiency was of about 93%. The proposed combined physical–chemical and biological processes for dairy effluents pretreatment allowed not only to reduce the effluents polluting load, but also to valorize wheys by producing valuable components.
Processed milk waste (MW) presents a serious problem within the dairy industries due to its high ... more Processed milk waste (MW) presents a serious problem within the dairy industries due to its high polluting load. Its chemical oxygen demand (COD) can reach values as high as 80,000 mg O L. This study proposes to reduce the organic load of those wastes using thermal coagulation and recover residual valuable components via fermentation. Thermal process results showed that the COD removal rates exceeded 40% when samples were treated at temperature above 60 °C to reach 72% at 100 °C. Clarified supernatants resulting from thermal treatment of the samples at the temperatures of 60 (MW), 80 (MW), and 100 °C (MW) were fermented using lactic acid bacteria strains without pH control. Lactic strains recorded important final cell yields (5-7 g L). Growth mediums prepared using the thermally treated MW produced 73% of the bacterial biomass recorded with a conventional culture medium. At the end of fermentation, mediums were found exhausted from several valuable components. Industrial scale implementation of the proposed process for the recycling of industrial MWs is described and discussed.
Residual fermented dairy products resulting from process defects or from expired shelf life produ... more Residual fermented dairy products resulting from process defects or from expired shelf life products are considered as waste. Thus, dairies wastewater treatment plants (WWTP) suffer high input effluents polluting load. In this study, fermented residuals separation from the plant wastewater is proposed. In the aim to meet the municipal WWTP input limits, a pretreatment combining physical–chemical and biological processes was investigated to reduce residual fermented dairy products polluting effect. Yoghurt (Y) and fermented milk products (RL) were considered. Raw samples chemical oxygen demand (COD) values were assessed at 152 and 246 g.L−1 for Y and RL products, respectively. Following the thermal coagulation, maximum removal rates were recorded at 80 °C. Resulting whey stabilization contributed to the removal rates enhance to reach 72% and 87% for Y and RL samples; respectively. Residual whey sugar content was fermented using Candida strains. Bacterial growth and strains degrading ...
Dairy industry effluents were usually characterized by their high organic matter content. Cheese ... more Dairy industry effluents were usually characterized by their high organic matter content. Cheese whey is the most wide studied dairy reject. Though, the high polluting dairy wastewater including product losses and process effluents are also problematic and they need to be treated separately. Despite the quite efficiency of physico-chemical processes, polluting load removal is typically insufficient and the treatment should be completed by a biological process. Lactose bioconversion to single cell proteins; lactic acid; citric acid; biopolymer, bioethanol or even hydrogen seem to be promoting alternatives, not only for the treatment but also for the recovery of valuable products. Anaerobic digestion using dark and/or photofermentation and microbial fuel cells exhibited several advantageous comparing to the conventional dairy wastewater processing pathways. Then, the microbial material role for the bioconversion is crucial and it should be done according to the treatment purposes. Saccharomyces, Klyveromyces and Candida strains are widely used for dairy wastewaters polluting load removal. Lactic acid bacteria are used for their biotechnological proprieties. Some mixed cultures proved to result in more efficient treatment results with valuable products.
Soft drink industries suffer inadequate handling of their product losses generally considered as ... more Soft drink industries suffer inadequate handling of their product losses generally considered as wastes. Those products contribute to the wastewater organic load augmentation and cause fastidious environmental impact. In this study, an industrial scale bioconversion process based on multistage fermentation was proposed to treat and reuse soft drink factories’ high-loaded effluents for valuable components production. An upstream segregation of non-consumed beverage was performed to reduce the organic load of the soft drink wastewater. Beverage characterization revealed an important sugar content. Such an organic compound is undoubtedly responsible of the high organic load of soft drink wastewater. Thus, the bioconversion of the sugar content of soft drink waste to single-cell proteins was proposed as a solution to reduce wastewater polluting load. Soft drink wastewater including rejected and returned products was tested to be used as a substrate for yeast biomass production using a commercial yeast strain of Saccharomyces cerevisiae. The effect of nutrient supplementation and the initial sugar concentration effect in culture media on the biomass production were investigated using batch and fed-batch process. Results indicated that supplementation is necessary for successful fermentation. Juices and nectars gave better sugar-biomass conversion yields (0.38–0.45 g g−1). Depletion of the sugar contained in the soft drinks exceeded 96 % for all fermented media. Fed-batch culture revealed a biomass concentration improvement reaching 9.16 g L−1 compared to batch biomass concentration resulting from batch cultures (5.2 g L−1). The proposed process was shown to enable beverage industries to reduce water pollution generation through an on-site segregation procedure and a storage system to valorize product losses as source medium for single-cell protein production.
Landfilling is one of the most widely used processes for the disposal of municipal solid waste (M... more Landfilling is one of the most widely used processes for the disposal of municipal solid waste (MSW). It is designed to dispose high quantities of waste at economical costs. Landfill management may pose serious environmental impacts through the discharge of highly polluted wastewater also known as leachate. The treatment of landfill leachates (LFL) is very complicated, expensive and requires various combined process applications due to their high COD and nitrogen levels.
Coffee processing byproducts are studied in this work for their valuable components. Spent coffee... more Coffee processing byproducts are studied in this work for their valuable components. Spent coffee grounds (SCG) and coffee silverskin (CSS) from Coffea arabica species were investigated for the determination of ethanol/water extracts bioactive molecules of interest. Phenolic compounds evaluation revealed that SCG enclose important amounts of polyphenols (8.425 mg GAE.g DW) and flavonoids (2.801 mg CE.g DW). Nevertheless, the highest levels of tannin (3.45 mg CE.g DW) were obtained with CSS. The total antioxidant activity of SCG was equal to 8.267 mg GAE.g DW, the DPPH test showed an IC50 value of 18 μg.ml -1 and the inhibition of β-carotene bleaching of IC50 was 600 μg.ml. While, the CSS showed better reducing power with an IC50 value of 120 μg.ml . Therefore, SCG proved to be more interesting than CSS regarding its antioxidant potentiality and its richness in phenolic compounds to be incorporated as food or therapeutic additive.
Cet ouvrage presente quelques alternatives de traitement et de valorisation des rejets des indust... more Cet ouvrage presente quelques alternatives de traitement et de valorisation des rejets des industries des boissons sucrees qui referment des teneurs en glucides assez importantes exploitables pour la production des microorganismes et des molecules a interet industriel. Les differents procedes proposent l’exploitation de ces produits comme matrice de production aussi bien de biomasse (ferments : bacteries, levures et moisissures) ou des molecules a usages divers (hydrogene, bioethanol, acides organiques, ...etc). L’utilisation de ces boissons comme milieux de culture permet d’epuiser les sucres initialement presents dans la matrice et aboutir par consequent, a un rejet industriel beaucoup moins polluant pour l’environnement. Ces substrats propres ouvrent des perspectives dans les poles de production des microorganismes et des molecules offrant aux marches de la fermentation, de la nutrition humaine et de la nutrition animale, des bacteries repondant aux normes de qualite y compris ce...
Kefir grains are a microbial consortium of different genera of bacteria and yeasts. In this study... more Kefir grains are a microbial consortium of different genera of bacteria and yeasts. In this study, the performance of Tunisian Kefir grains during the biological treatment of a mixture of Gouda cheese whey and white wastewaters (GCW) in ratio 1:1 with very high organic matter concentration is investigated. The biological process was evaluated and optimized through the response surface methodology. Under the optimum conditions, Kefir grains concentration of 1.02%, temperature at 36.68 °C, and incubation time of 5.14 days, the removal efficiencies of COD, PO 4 3− , and NO 3 − were 87, 37.48, and 39.5%, respectively. Interestingly, the reusability tests of the grains proved not only their high resistance to harsh environmental conditions but also their great potential for more practical applications. Particularly, different strains were isolated from the grains and identified as Kluyveromyces marxianus , Lactoccocus lactis , Lactobacillus kefiri , and Bacillus spp. using 16S rDNA sequence analysis and rep-PCR fingerprinting. At the biological level, the raw GCW (RGCW) has a negative impact on the Hordeum vulgare both on seed germination, and on the growth parameters of seedlings. Interestingly, after Kefir grains treatment, the treated GCW (TGCW) allow a seedlings growth and germination rate similar to those soaked in water.
In this study the biotreatability of Jebel Chakir landfill leachate (Tunisia) using a mixture of ... more In this study the biotreatability of Jebel Chakir landfill leachate (Tunisia) using a mixture of dairy industry reject (bactofugate) and Aloe sp. leaf gel was evaluated. The effect of Aloe gel fermentation using Saccharomyces cerevisiae yeast strain was investigated against some selected bacterial and fungal strains. The inoculation size effect of the treatment mixtures (2, 6, 10 and 12%) in the treatment efficiency was also studied. The obtained results showed that when natural Aloe gel and bactofugate mixtures were used the recorded chemical oxygen demand removal rates exceeded 56% within 48 h of treatment. Whereas, the use of the fermented Aloe gel in the treatment mixtures has promoted the organic matter removal to reach 72%.
The wastewater from the dumping site usually contains high pollutant levels. Biological process a... more The wastewater from the dumping site usually contains high pollutant levels. Biological process and physico-chemical treatments are among several technologies for wastewater treatment. Using microorganisms in the treatment of landfill leachate is an emerging research issue. Furthermore, bioremediation is a feasible approach for pollutants removal from landfill leachate which would provide an efficient way to resolve the issue of landfill leachate. In this study, the performance of yeast and bacteria isolated from kefir grains was assessed for landfill leachate treatment. Kefir grains microbial composition was evaluated by molecular approaches (Rep-PCR and 16S rRNA gene sequencing). The obtained outcomes denoted that high concentrations of lactic acid bacteria and yeast populations (over 107 CFU/mL) were found in the kefir grains and were essentially composed of Lactococcus lactis, Lactobaccillus kefirien, bacillus sp., Lactococcus lactis and Kluyveromyces marxianus. The co-culture with 1% of inoculum size was demonstrated as the most efficient in the degradation of different contaminants. The overall abatement rate of chemical oxygen demand (COD), ammonium nitrogen (NH4 + -N) and salinity were 75.8%, 85.9% and 75.13%, respectively. The bioremediation process resulted in up of 75% removal efficiency of Ni and Cd, and a 73.45, 68.53 and a 58.17% removal rates of Cu, Pb and Fe, respectively. The research findings indicate the performance of L. lactis and K. marxianus co-culture isolated from kefir grains for the bioremediation of LFL.
This research was carried for the coproduction of two industrial enzymes: α-amylase and protease ... more This research was carried for the coproduction of two industrial enzymes: α-amylase and protease via SSF by Rhizopus oryzae on humidified bread waste. Fermentation time, inoculum size, initial moisture content, salt solutions, and the thickness of the substrate were investigated one by one. Fungus culture was carried out in sterile aluminum trays, and pH was adjusted to 5.5. The main results showed that the highest levels of enzyme production were obtained at 120 h, 65% relative humidity, height media of 1 cm, 105 spore/g, and M-9 solution (g/L): NaH2PO4, 12.8; KH2PO4, 3; NaCl, 0.5; NH4Cl, 1; MgSO4 7H2O, 0.5; CaCl2 2H2O, 0.01. α-Amylase (100 U/g) and protease (2400 U/g) produced by SSF from Rhizopus oryzae (CH4) on BW as substrate are of great interest in industries and could be valorized as enhancers of the bread making process.
This study investigates the performance of the combination of biological pre-treatment with Kefir... more This study investigates the performance of the combination of biological pre-treatment with Kefir grains (KGs) and photocatalytic process using Ag-doped TiO2 nanoparticles (NPs) for the simultaneous removal of toxic pollutants from landfill leachate (LFL). After 5 days of 1% (w/v) KGs pre-treatment at 37 °C, TOC, COD, NH4+-N, and PO43- removal rates were 93, 83.33, 70 and 88.25%, respectively. The removal efficiencies were found to be 100, 94, 62.5, 53.16 and 47.52 % for Cd, Ni, Zn, Mn and Cu, respectively. The optimal conditions of Ag-doped TiO2 photocatalytic process were optimized using Box-Behnken design and response surface methodology (BBD-RSM) to enhance the quality of pre-treated LFL. Interestingly, Ag-doped TiO2 photocatalytic process increases the overall removal efficiencies to 98, 96, 85 and 93% of TOC, COD, NH4+-N, and PO43-, respectively. Furthermore, the removal efficiency of toxic heavy metals was gradually improved. In addition, KGs and Ag-doped TiO2 exhibited excellent recyclability showing the potential of combined biological/photocatalytic process to treat hazardous LFL.
Abstract In this work, the feasibility of baker yeast production using white bread waste is inves... more Abstract In this work, the feasibility of baker yeast production using white bread waste is investigated. Grinded and sieved white baguette waste was hydrated and hydrolyzed differently using enzymes preparations to obtain two growth mediums. Medium (I) contained a mixture of alpha amylase and amyloglucosidase; and Medium (II) contained a mixture of alpha amylase, amyloglucosidase and protease enzymes. The clarified media were diluted and supplemented with NH4SO4 (3.5 g/l), and KH2PO4 (2 g/l). A commercial baker yeast strain was reactivated and a preculture was prepared for the mediums inoculation. Fermentation was carried out in Erlenmeyer flasks and incubated in the thermo-shaker (30 °C, 150 rpm). After 48 h of fermentation, important biomass production was recorded in Mediums (I) and (II) (1.04 × 108 CFU/ml and 2.74 × 108 CFU/ml) compared to the control medium (1.63 × 108 CFU/ml). Hence, the productivity ratio of Medium I and Medium II was estimated to be 0.63 and 1.68. Microbial growth, sugars and proteins consumption kinetics were studied. The obtained results indicated that the production of yeast biomass could be an attractive alternative for bread waste valorization ensuring a global biomass yield of 0.77 g/g.
Residuals are responsible for the polluting load increase of soft drink industry wastewater due t... more Residuals are responsible for the polluting load increase of soft drink industry wastewater due to their high sugar contents. The present work proposes an upstream segregation of residuals to be biologically treated by the bioconversion of their carbohydrates content into baker's yeast biomass. Carbonated soft drinks (CSD) and nectars and juices (NJ) ranges were considered. Different incorporation ratios of NJ in the CSD (0–75%) have been investigated for balanced growth medium. Despite the nitrogen deficiency of media, results showed that NJ incorporation promoted the microbial growth. Media containing more than 50% of NJ exhibited ∼25% sugar-biomass conversion rates. The chemical oxygen demand (COD) of the media exceeded 70% at the end of fermentation. Moreover, valuable components were recovered by yeast production. Nutrient consumption rates varied from 65.4% for sugar and calcium content to in excess of 99% for protein and other minerals. In order to investigate an availabl...
The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella ... more The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella sp.) cultivation was investigated in this study. Landfill leachate was collected from Borj Chakir landfill, Tunisia. A full factorial experimental design 22 was proposed to study the effects of the incubation time and leachate ratio factors on the organic matter removal expressed in chemical oxygen demand (COD) and ammoniacal nitrogen (NH4─N) and on the biological response of Chlorella sp. expressed by the cell density and chlorophyll content. All experiments were batch runs at ambient temperature (25 ± 2 °C). The Chlorella sp. biomass and chlorophyll a concentrations of 1.2 and 5.32 mg L−1, respectively, were obtained with 10% leachate spike ratio. The obtained results showed that up to 90% of the ammoniacal nitrogen in landfill leachate was removed in 10% leachate ratio spiked medium with a residual concentration of 40 mg L−1. The maximum COD removal rate reached 60% within 13 days of incubation time indicating that microalgae consortium was quite effective for treating landfill leachate organic contaminants. Furthermore, with the 10% leachate ratio spiked medium, the maximum lipid productivity was 4.74 mg L−1 d−1. The present study provides valuable information for potential adaptation of microalgae culture and its contribution for the treatment of Tunisian landfill leachate.
This work proposes a novel approach for the reuse and the recovery of dairy wastes valuable compo... more This work proposes a novel approach for the reuse and the recovery of dairy wastes valuable components. Thermal coagulation was performed for dairy effluents and the main responsible fraction for the organic matter content (protein and fat) was separated. Dairy curds were prepared for the formulation of bacterial growth media. Protein, sugar, fat and fatty acids contents have been assessed. Samples treated at 100 °C exhibited marked improvement in terms of protein (25-50%) recovery compared to those treated at 80 °C. Fatty acid analysis revealed the presence of unsaturated fatty acids (mainly oleic acid) that are essential to promote Lactobacillus growth. Previously isolated and identified bacterial strains from dairy wastes (Lactobacillus paracasei, Lactobacillus plantarum, Lactococcus lactis and Lactobacillus brevis) were investigated for their ability to grow on the formulated media. All the tested lactic acid bacteria exhibited greater bacterial growth on the formulated media su...
International Journal of Environmental Science and Technology
Among dairy effluents, bactofugate (B) and decreaming racking water (D) were identified as the mo... more Among dairy effluents, bactofugate (B) and decreaming racking water (D) were identified as the most polluting due to their organic load content expressed in the chemical oxygen demand (156–240 g·L−1). Joining the plant wastewater, such effluents contribute to the increase of the polluting load of the wastewater treatment plant input which disturbs the treatment performance. This work proposes an upstream segregation of those dairy effluents for combined physical–chemical and biological treatment. An experimental design was proposed to investigate initial pH, applied temperature and exposure time factor effects on the thermal coagulation process. The fermentation of the resulted supernatants using Lactobacillus lactis ssp. lactis was performed. The optimized thermal coagulation pretreatment was obtained at (pH; T(°C); t(min)): 6, 60 °C and 5 min, with both (B) and (D) effluents. Resulted clarified whey sugar, protein and fat contents were assessed. The physical–chemical treatment resulted in considerable organic matter removal: 45% for (B) samples and 31% for (D) samples of proteins content and almost the total fat content. However, there is no considerable effect on the sugar content reduction, which remains responsible for the major fraction of the whey residual chemical oxygen demand (COD). Clarified whey fermentation using Lactococcus lactis ssp. lactis strain induced important sugar consumption rates. Therefore, important sugar consumption rates were recorded and the COD removal efficiency was improved. The recorded global COD removal efficiency was of about 93%. The proposed combined physical–chemical and biological processes for dairy effluents pretreatment allowed not only to reduce the effluents polluting load, but also to valorize wheys by producing valuable components.
Processed milk waste (MW) presents a serious problem within the dairy industries due to its high ... more Processed milk waste (MW) presents a serious problem within the dairy industries due to its high polluting load. Its chemical oxygen demand (COD) can reach values as high as 80,000 mg O L. This study proposes to reduce the organic load of those wastes using thermal coagulation and recover residual valuable components via fermentation. Thermal process results showed that the COD removal rates exceeded 40% when samples were treated at temperature above 60 °C to reach 72% at 100 °C. Clarified supernatants resulting from thermal treatment of the samples at the temperatures of 60 (MW), 80 (MW), and 100 °C (MW) were fermented using lactic acid bacteria strains without pH control. Lactic strains recorded important final cell yields (5-7 g L). Growth mediums prepared using the thermally treated MW produced 73% of the bacterial biomass recorded with a conventional culture medium. At the end of fermentation, mediums were found exhausted from several valuable components. Industrial scale implementation of the proposed process for the recycling of industrial MWs is described and discussed.
Residual fermented dairy products resulting from process defects or from expired shelf life produ... more Residual fermented dairy products resulting from process defects or from expired shelf life products are considered as waste. Thus, dairies wastewater treatment plants (WWTP) suffer high input effluents polluting load. In this study, fermented residuals separation from the plant wastewater is proposed. In the aim to meet the municipal WWTP input limits, a pretreatment combining physical–chemical and biological processes was investigated to reduce residual fermented dairy products polluting effect. Yoghurt (Y) and fermented milk products (RL) were considered. Raw samples chemical oxygen demand (COD) values were assessed at 152 and 246 g.L−1 for Y and RL products, respectively. Following the thermal coagulation, maximum removal rates were recorded at 80 °C. Resulting whey stabilization contributed to the removal rates enhance to reach 72% and 87% for Y and RL samples; respectively. Residual whey sugar content was fermented using Candida strains. Bacterial growth and strains degrading ...
Dairy industry effluents were usually characterized by their high organic matter content. Cheese ... more Dairy industry effluents were usually characterized by their high organic matter content. Cheese whey is the most wide studied dairy reject. Though, the high polluting dairy wastewater including product losses and process effluents are also problematic and they need to be treated separately. Despite the quite efficiency of physico-chemical processes, polluting load removal is typically insufficient and the treatment should be completed by a biological process. Lactose bioconversion to single cell proteins; lactic acid; citric acid; biopolymer, bioethanol or even hydrogen seem to be promoting alternatives, not only for the treatment but also for the recovery of valuable products. Anaerobic digestion using dark and/or photofermentation and microbial fuel cells exhibited several advantageous comparing to the conventional dairy wastewater processing pathways. Then, the microbial material role for the bioconversion is crucial and it should be done according to the treatment purposes. Saccharomyces, Klyveromyces and Candida strains are widely used for dairy wastewaters polluting load removal. Lactic acid bacteria are used for their biotechnological proprieties. Some mixed cultures proved to result in more efficient treatment results with valuable products.
Soft drink industries suffer inadequate handling of their product losses generally considered as ... more Soft drink industries suffer inadequate handling of their product losses generally considered as wastes. Those products contribute to the wastewater organic load augmentation and cause fastidious environmental impact. In this study, an industrial scale bioconversion process based on multistage fermentation was proposed to treat and reuse soft drink factories’ high-loaded effluents for valuable components production. An upstream segregation of non-consumed beverage was performed to reduce the organic load of the soft drink wastewater. Beverage characterization revealed an important sugar content. Such an organic compound is undoubtedly responsible of the high organic load of soft drink wastewater. Thus, the bioconversion of the sugar content of soft drink waste to single-cell proteins was proposed as a solution to reduce wastewater polluting load. Soft drink wastewater including rejected and returned products was tested to be used as a substrate for yeast biomass production using a commercial yeast strain of Saccharomyces cerevisiae. The effect of nutrient supplementation and the initial sugar concentration effect in culture media on the biomass production were investigated using batch and fed-batch process. Results indicated that supplementation is necessary for successful fermentation. Juices and nectars gave better sugar-biomass conversion yields (0.38–0.45 g g−1). Depletion of the sugar contained in the soft drinks exceeded 96 % for all fermented media. Fed-batch culture revealed a biomass concentration improvement reaching 9.16 g L−1 compared to batch biomass concentration resulting from batch cultures (5.2 g L−1). The proposed process was shown to enable beverage industries to reduce water pollution generation through an on-site segregation procedure and a storage system to valorize product losses as source medium for single-cell protein production.
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Papers by Mariam Kasmi