- Al Ain, Abu Dhabi, United Arab Emirates
The biological treatment of emulsified oils, using bacteria, has gained a lot of attention and its effectiveness has been widely proven. This is a very important process, as emulsified oils are considered a major environmental hazard.... more
The biological treatment of emulsified oils, using bacteria, has gained a lot of attention and its effectiveness has been widely proven. This is a very important process, as emulsified oils are considered a major environmental hazard. However, the produced biomass, i.e., bacteria, does not have any obvious value. One the other hand, if oils can be removed by microalgae, the produced biomass in this case can be readily used to produce lipids, proteins and pigments. The former product can be used for biodiesel production and the latter two products have potential to be used in pharmaceutical and food applications. The ability of two marine strains, namely Nannochloropsis sp. and Tetraselmis sp . to grow in water containing emulsified oil has been tested. The effectiveness of the selected strains to utilize the organics as a carbon source and reduce their concentration has also been assessed. The oil removal efficiency and cells growth rates were evaluated. In the tested condition, the...
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α-Amylase and β-glucosidase are key enzymes involved in carbohydrates breakdown and intestinal absorption, respectively. Inhibition of these enzymes hinders blood glucose level increase after a carbohydrate diet and can be an important... more
α-Amylase and β-glucosidase are key enzymes involved in carbohydrates breakdown and intestinal absorption, respectively. Inhibition of these enzymes hinders blood glucose level increase after a carbohydrate diet and can be an important strategy in the management of non-insulin-dependent diabetes mellitus (NIDDM). A main drawback of currently used inhibitors is their side effects such as abdominal distention, flatulence, meteorism and diarrhea, caused by excessive inhibition of pancreatic α-amylase resulting in abnormal bacterial fermentation of undigested carbohydrates in the colon. Natural inhibitors from plants have shown lower inhibitory effect against α-amylase activity and a stronger inhibitory activity against α-glucosidase and can be used as effective therapy for NIDDM with minimal side effects. In this work dates-extract (DE) inhibitory effect on α-amylase and α-glucosidase has been assessed. The inhibition percentages on α-amylase and α-glucosidase were in the range of 6-24...
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Electrocoagulation is a process that involves dissolution of a metal anode with simultaneous formation of hydroxyl ions and hydrogen gas at the cathode. It has recently attracted the attention of many industries as a potential technique... more
Electrocoagulation is a process that involves dissolution of a metal anode with simultaneous formation of hydroxyl ions and hydrogen gas at the cathode. It has recently attracted the attention of many industries as a potential technique for the treatment and purification of several types of highly contaminated wastewater. In this study, electrocoagulation has been evaluated as a treatment process for the reduction of high concentrations of COD in petroleum refinery wastewater. Experiments were carried out in the continuous mode using an electrocoagulation reactor with aluminum electrodes. The effects of key operating parameters such current density, pH, initial COD content and the inlet flow rate were investigated. The reduction of COD content was significantly improved by increasing the current density and reducing the feed flow rate. The reactor performance was optimized at a neutral pH, in the range of 6-8, and ambient temperature of about 25 o C. The results demonstrated the tec...
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Mostconventionaltechniquesforthedeterminationofmicroalgaelipidcontentaretimeconsumingandinmostcasesareindirectandrequireexcessivesamplepreparations.Thisworkpresentsanewtechniquethatutilizes radio frequency (RF) for rapid lipid... more
Mostconventionaltechniquesforthedeterminationofmicroalgaelipidcontentaretimeconsumingandinmostcasesareindirectandrequireexcessivesamplepreparations.Thisworkpresentsanewtechniquethatutilizes radio frequency (RF) for rapid lipid quantification, without the need for sample preparation. TestsshowedthatashiftintheresonancefrequencyofaRFopen-endedcoaxialresonatorandagradualincreasein its resonance magnitude may occur as the lipids content of microalgae cells increases. These responseparameterscanbethencalibratedagainstactualcellularlipidcontentsandusedforrapiddeterminationofthecellularlipids.Theaveragedurationoflipidquantificationusingtheproposedtechniquewasofabout1minute,whichissignificantlylessthanallotherconventionaltechniques,andwasachievedwithouttheneedfor any time consuming treatment steps.
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Cyclodextrins (CDs) and their derivatives have attracted significant attention in the pharmaceutical, food, and textile industries, which has led to an increased demand for their production. CD is typically produced by the action of... more
Cyclodextrins (CDs) and their derivatives have attracted significant attention in the pharmaceutical, food, and textile industries, which has led to an increased demand for their production. CD is typically produced by the action of cyclodextrin glycosyltransferase (CGTase) on starch. Owing to the relatively high cost of enzymes, the economic feasibility of the entire process strongly depends on the effective retention and recycling of CGTase in the reaction system, while maintaining its stability. CGTase enzymes immobilized on various supports such as porous glass beads or glyoxyl-agarose have been previously used to achieve this objective. Nevertheless, the attachment of biocatalysts on conventional supports is associated with numerous drawbacks, including enzyme leaching prominent in physical adsorption, reduced activity as a result of chemisorption, and increased mass transfer limitations. Recent reports on the successful utilization of metal–organic frameworks (MOFs) as support...
Biodiesel is a promising candidate for sustainable and renewable energy and extensive research is being conducted worldwide to optimize its production process. The employed catalyst is an important parameter in biodiesel production.... more
Biodiesel is a promising candidate for sustainable and renewable energy and extensive research is being conducted worldwide to optimize its production process. The employed catalyst is an important parameter in biodiesel production. Metal–organic frameworks (MOFs), which are a set of highly porous materials comprising coordinated bonds between metals and organic ligands, have recently been proposed as catalysts. MOFs exhibit high tunability, possess high crystallinity and surface area, and their order can vary from the atomic to the microscale level. However, their catalytic sites are confined inside their porous structure, limiting their accessibility for biodiesel production. Modification of MOF structure by immobilizing enzymes or ionic liquids (ILs) could be a solution to this challenge and can lead to better performance and provide catalytic systems with higher activities. This review compiles the recent advances in catalytic transesterification for biodiesel production using e...
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Crude petroleum oil spills are among the most important organic contaminations. While the separated oils accumulated on the surface water are relatively easily removed, the emulsified portions are more difficult to remove and pose... more
Crude petroleum oil spills are among the most important organic contaminations. While the separated oils accumulated on the surface water are relatively easily removed, the emulsified portions are more difficult to remove and pose significant threats to the environment. Bioremediation using bacteria has proven to be an effective method, but the biomass produced in this case does not have any significant remunerative value. In this work, microalgae were proposed to combine emulsified oil remediation process with the potential of microalgae as a biofuel feedstock, thus enhancing the economic and environmental benefits of the process. A freshwater strain of Chlorella vulgaris was grown in water containing different concentrations of emulsified crude oil at different temperatures. The specific growth rate (μmax) of the microalgae for each initial oil concentration was determined and was found to increase with the increase in initial oil concentration. For example, at 30°C, the specific growth rate, μ increased from 0.477 to 0.784 per day as the oil concentration increased from 57 to 222 mg/L. At 30°C, the effect of substrate concentration agreed with that of the microalgae growth, whereas at 40°C, the drop in oil concentration decreased with the increase in concentration. The results were fitted to a modified Monod kinetics model that used specific interfacial area as the influential substrate instead of the actual concentration. The results of this study clearly show the potential of using microalgae for emulsified oil remediation at relatively high concentrations.
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Green building regulations in the United Arab Emirates are required to obtain building permits so that future construction projects can create a sustainable living environment. Emirates such as Abu Dhabi, Dubai, and Sharjah have specific... more
Green building regulations in the United Arab Emirates are required to obtain building permits so that future construction projects can create a sustainable living environment. Emirates such as Abu Dhabi, Dubai, and Sharjah have specific green building regulations, whereas other emirates follow Abu Dhabi’s regulatory criteria. Previous work fails to present a techno-economic cross-code analysis for various green building regulations in the UAE by evaluating energy and water performance. A case study using an existing high-rise green office building was formulated using the Integrated Environmental Solution: Virtual Environment (IES-VE) platform and the U.S. Leadership in Energy and Environmental Design (U.S. LEED) water consumption evaluation tool to study its energy and water performance, respectively. The archived results were used to devise an economic study based on the discounted cash flow technique. The principal findings of this research allowed us to determine a cross-code a...
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Lipids, proteins, and carbohydrates are the major constituents found in microalga cells, in varying proportions, and these biomolecules find applications in different industries. During microalga cultivation, to efficiently manipulate,... more
Lipids, proteins, and carbohydrates are the major constituents found in microalga cells, in varying proportions, and these biomolecules find applications in different industries. During microalga cultivation, to efficiently manipulate, control, and optimize the productivity of a specific compound for a specific application, real‐time monitoring of these three cell components is essential. In this study, a method using measurement of electrical capacitance was developed to simultaneously determine the lipid, protein, and carbohydrate content of microalga cells without the requirement for any pre‐processing steps. The marine microalga Nannochloropsis oculata was cultivated under nitrogen starvation conditions to induce lipid accumulation over a period of 22 days. The correlation between the electrical capacitance of the microalga culture and the intracellular biomolecule content (determined by standard techniques) was investigated, enabling subsequent deduction of microalga intracellular content from electrical capacitance of the culture. The accuracy and precision of the technique were proven by validating an independent sample. The main advantage of the proposed technique is its capability of quantifying microalga composition within a few minutes, significantly faster than currently available conventional techniques.
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ABSTRACT Commercial applications of enzymatic biodiesel production have been hindered by the enzyme's high cost and poor reusability. Ionic liquids (ILs) have been proposed as alternatives to organic solvents conventionally used in... more
ABSTRACT Commercial applications of enzymatic biodiesel production have been hindered by the enzyme's high cost and poor reusability. Ionic liquids (ILs) have been proposed as alternatives to organic solvents conventionally used in enzymatic biodiesel production. In this work, the reusability of an enzyme-IL system was tested at different methanol-to-oil molar ratios for four consecutive cycles, of 60 and 120 min each. Extracting biodiesel alone by n-hexane resulted in a sharp drop in the overall activity due to the accumulation of the by-product, glycerol. Extracting glycerol by 1-butanol enhanced the stability and allowed the enzyme-IL to be used successfully for four cycles. This study also shows the effect of methanol inhibition on the enzyme stability. The results of this work provide important information for the success of using enzyme-IL systems for biodiesel production, which is essential for the process to be economic.
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Increasing attention has been recently focused on producing biodiesel from non-edible organic materials to avoid competing on food sources. The focus of the present work is to assess the possibility of extracting oils from date seeds... more
Increasing attention has been recently focused on producing biodiesel from non-edible organic materials to avoid competing on food sources. The focus of the present work is to assess the possibility of extracting oils from date seeds (DS), which is a waste biomass that can then be used in biodiesel production. Two cultivars of local date seeds, namely, Khalas and Allig, have been used. Oil was extracted by Soxhlet and Folch methods from DS particles in five size ranges (300 nm, 0.1–0.3 mm, 0.3–0.85 mm, 0.85–1.18 mm, and > 1.18 mm) and compared to ungrounded DS. The size of the DS particles was found to have a clear effect on the oil extraction yield percentage (OEYP), which increased with the decrease in the particles size, excluding the nano-particles at which the OEYP reduced. The maximum OEYPs were achieved from Allig DS in the size range of 0.1–0.3 mm, which were 9.0 and 10.4%, using the Folch and Soxhlet extractions, respectively. The same size range, the maximum OEYPs, was also achieved from Khalas DS and was very close to those achieved from the Allig DS. The Soxhlet extraction was generally more effective than the Folch extraction in all size ranges. The difference in the effectiveness was minimum in the size range of 0.1–0.3 mm, and increased as the particles’ size increased. In the Folch process, the effects of the duration of main steps, namely, the ultra-sonication, orbital shaking, and centrifugation, on the OEYP, were evaluated. Using Allig DS in the size range of 0.1–0.3 mm, the effects of the times of ultra-sonication, above 1 min, and centrifugation on OEYP were insignificant, whereas the orbital shaking time had a slight negative effect. This work provides important information of the extraction process of oils from DS, and brings their use for biodiesel production closer to commercialization.
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Abstract Biodiesel is a promising sustainable alternative to non-renewable petrodiesel. In this work, oils extracted from microalgae are used for biodiesel production. To simplify the process, the extraction of the oils and their reaction... more
Abstract Biodiesel is a promising sustainable alternative to non-renewable petrodiesel. In this work, oils extracted from microalgae are used for biodiesel production. To simplify the process, the extraction of the oils and their reaction are made to take place simultaneously in one step. Immobilized lipase was used as the catalyst, and supercritical CO2 (SC-CO2) was used as an extraction solvent and reaction medium. The use of SC-CO2 allows easy separation of the products and leaves the leftover biomass uncontaminated, allowing it to be utilized in food and pharmaceutical applications. The effects of temperature (35–50 °C), reaction time (2-6 h), and methanol:oil (M:O) molar ratio (8:1–16:1) on biodiesel yield were investigated. Within 6 h, the maximum biodiesel production yield was found to be 19.3% at a temperature of 35 °C and at an M:O molar ratio of 8:1. The results hold promise in simplifying the microalgae-to-biodiesel production process.
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Microalgae are promising sustainable and renewable sources of oils that can be used for biodiesel production. In addition, they contain important compounds, such as proteins and pigments, which have large applications in the food and... more
Microalgae are promising sustainable and renewable sources of oils that can be used for biodiesel production. In addition, they contain important compounds, such as proteins and pigments, which have large applications in the food and pharmaceutical industries. Combining the production of these valuable products with wastewater treatment renders the cultivation of microalgae very attractive and economically feasible. This review paper presents and discusses the current applications of microalgae cultivation for wastewater treatment, particularly for the removal of phenolic compounds. The effects of cultivation conditions on the rate of contaminants removal and biomass productivity, as well as the chemical composition of microalgae cells are also discussed.
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Activated carbon (AC) is a common adsorbent that is used in both artificial and bioartificial liver devices. Three natural materials - date pits of (fruit), (jojoba) seeds, and spp. (microalgae) - were used in the present investigation as... more
Activated carbon (AC) is a common adsorbent that is used in both artificial and bioartificial liver devices. Three natural materials - date pits of (fruit), (jojoba) seeds, and spp. (microalgae) - were used in the present investigation as precursors for the synthesis of AC using physical activation. The chemical structures and morphology of AC were analyzed. Then, AC's bilirubin adsorption capacity and its cytotoxicity on normal liver (THLE2) and liver cancer (HepG2) cells were characterized. Compared with the other raw materials examined, date-pit AC was highly selective and showed the most effective capacity of bilirubin adsorption, as judged by isotherm-modeling analysis. MTT in vitro analysis indicated that date-pit AC had the least effect on the viability of both THLE2 and HepG2 cells compared to jojoba seeds and microalgae. All three biomaterials under investigation were used, along with collagen and Matrigel, to grow cells in 3D culture. Fluorescent microscopy confirmed d...
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There is an increasing need to find natural bioactive compounds for pharmaceutical applications, because they have less harmful side effects compared to their chemical alternatives. Microalgae (MA) have been identified as a promising... more
There is an increasing need to find natural bioactive compounds for pharmaceutical applications, because they have less harmful side effects compared to their chemical alternatives. Microalgae (MA) have been identified as a promising source for these bioactive compounds, and this work aimed to evaluate the anti-proliferative effects of semi-purified protein extracted from MA against several tumor cell lines. Tested samples comprised MA cell extracts treated with cellulase and lysozyme, prior to extraction. The effect of dialysis, required to remove unnecessary small molecules, was also tested. The anti-cancer efficacies of the dialyzed and undialyzed extracts were determined by measuring cell viability after treating four human cancer cell lines, specifically A549 (human lung carcinoma), MCF-7 (human breast adenocarcinoma), MDA MB-435 (human melanoma), and LNCap (human prostate cancer cells derived from a metastatic site in the lymph node). This was compared to the effects of the ag...
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Treatment of municipal wastewater, which involves multiple steps, produces large amounts of bio-solid sludge, which is either incinerated or disposed in landfills. This sludge contains carbon, nitrogen, and phosphorous in appreciable... more
Treatment of municipal wastewater, which involves multiple steps, produces large amounts of bio-solid sludge, which is either incinerated or disposed in landfills. This sludge contains carbon, nitrogen, and phosphorous in appreciable amounts, and hence, it is being recently suggested that it should be used as a fertilizer. However, the bio-solid sludge also contains large amounts of heavy metals, which exert harmful effects on the plantation, and therefore, they must be removed before it can be used as a fertilizer. In addition, some of these heavy metals are precious such as gold. In this work, heavy metals present in the bio-solid sludge produced from municipal wastewater plants were extracted using acidic solutions of different strengths. The method of selected gold extraction using tributyl phosphate (TBP) in kerosene solution from the metal rich acidic solution was also tested. The rate and yield of gold extraction in-crease with the increase in the acidic strength. The highest...
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ABSTRACT In biodiesel production, catalyzed by immobilized lipase, a solvent is needed to reduce the inhibition effects caused by excessive use of short-chain alcohols and deposited glycerol. Volatile and toxic organic chemicals are... more
ABSTRACT In biodiesel production, catalyzed by immobilized lipase, a solvent is needed to reduce the inhibition effects caused by excessive use of short-chain alcohols and deposited glycerol. Volatile and toxic organic chemicals are commonly used to achieve this by enhancing the solubility of the alcohols and glycerol. In this work, non-volatile ionic liquids (ILs) are proposed as alternative solvents, which are safer and easier to recycle. Several ILs were tested and their effectiveness was compared to that of the conventional solvents, n-hexane and tert-butanol. Hydrophobic ILs showed much more promising results and much higher biodiesel production yields compared to hydrophilic ILs. A set of experiments was designed using full factorial (33) experimental design to statistically evaluate the results. The effects of reaction temperature, methanol-to-oil molar ratio and enzyme loading were considered. Response surface methodology (RSM) was then used to optimize process variables. The highest yields of 72 and 48% were achieved after 14 hrs of reaction at 50°C, 6:1 molar ratio and 40% enzyme loading in [bmim][PF6] and [bmim][NTf2], respectively. Regression models were developed to predict the optimal production yields and found to be adequate and statistically acceptable.
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The performance of an adsorption column packed with granular activated carbon was evaluated for the removal of phenols from refinery wastewater. The effects of phenol feed concentration (80-182 mg/l), feed flow rate (5-20 ml/min), and... more
The performance of an adsorption column packed with granular activated carbon was evaluated for the removal of phenols from refinery wastewater. The effects of phenol feed concentration (80-182 mg/l), feed flow rate (5-20 ml/min), and activated carbon packing mass (5-15 g) on the breakthrough characteristics of the adsorption system were determined. The continuous adsorption process was simulated using batch data and the parameters for a new empirical model were determined. Different dynamic models such as Adams-Bohart, Wolborsko, Thomas, and Yoon-Nelson models were also fitted to the experimental data for the sake of comparison. The empirical, Yoon-Nelson and Thomas models showed a high degree of fitting at different operation conditions, with the empirical model giving the best fit based on the Akaike information criterion (AIC). At an initial phenol concentration of 175 mg/l, packing mass of 10 g, a flow rate of 10 ml/min and a temperature of 25 °C, the SSE of the new empirical and Thomas models were identical (248.35) and very close to that of the Yoon-Nelson model (259.49). The values were significantly lower than that of the Adams-Bohart model, which was determined to be 19,358.48. The superiority of the new empirical model and the Thomas model was also confirmed from the values of the R (2) and AIC, which were 0.99 and 38.3, respectively, compared to 0.92 and 86.2 for Adams-Bohart model.
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Abstract A three-step pilot plant was designed, fabricated and tested for the treatment of highly contaminated petroleum refinery wastewater. The three-step process consisted of an electrocoagulation (EC) unit, a biological treatment in a... more
Abstract A three-step pilot plant was designed, fabricated and tested for the treatment of highly contaminated petroleum refinery wastewater. The three-step process consisted of an electrocoagulation (EC) unit, a biological treatment in a spouted bed bioreactor (SBBR) using immobilized Pseudomonas putida in PVA particles, and an adsorption process using granular activated carbon in a packed column. The pilot plant was operated for a period of ten months at a flow rate of 1 m3/h, with continuous runs lasting up to 12 h. Different arrangements of the three units were tested to determine the most effective sequence. Placing the EC unit as the pretreatment step resulted in the best performance, since it reduced the COD and suspended solids, and consequently enhanced the performance of the succeeding biodegradation and adsorption units. At the optimum conditions and unit arrangement, the pilot plant was able to reduce the COD by 96% and the concentrations of phenol and cresols by nearly 100%.
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ABSTRACT Enzymatic biodiesel production in supercritical CO2 (SC-CO2) has recently received an increasing attention, as an alternative to the conventional chemical processes. In this study, enzymatic production of biodiesel from... more
ABSTRACT Enzymatic biodiesel production in supercritical CO2 (SC-CO2) has recently received an increasing attention, as an alternative to the conventional chemical processes. In this study, enzymatic production of biodiesel from microalgal lipids was investigated in batch and integrated extraction-reaction systems. In the batch system, the effect of enzyme loading (15-50% wt), temperature (35-55 °C) and methanol to lipid molar ratios (3-15:1) were studied, and response surface methodology was employed to optimize selected factors effect. The optimum transesterification yield of 80%, was obtained at 50 °C, 200 bar, 35% enzyme loading, and 9:1 molar ratio after 4 h reaction in the batch system. The experimental results were also used to determine the kinetics parameters of the Ping-Pong Bi Bi model, with methanol inhibition, suggested to describe the reaction. In the continuous integrated extraction-reaction system, the effect of methanol to lipids molar ratio was investigated, and enzyme operational stability and reusability were tested. Bed regeneration by tert-butanol washing was also assessed. The optimum methanol to lipid ratio was found to be 10: 1. At this ratio, the enzyme was able to attain 78% of its original activity when reused for 6 continuous cycles, and the bed was successfully reused by washing with tert-butanol.