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The effectiveness of a recycling approach of the printed circuit board (PCBs), and, thus, the quality of polymeric constituents, primarily rests on the capacity to eliminate the bromine content (mainly as HBr). HBr is emitted in appreciable quantities during thermal decomposition of PCB-contained brominated flame retardants (BFRs). The highly corrosive, yet relatively reactive HBr, renders recovery of bromine-free hydrocarbons streams from brominated polymers in PCBs very challenging. Via combined experimental and theoretical frameworks, this study explores the potential of deploying alumina (Al2O3) as a debromination agent of Br-containing hydrocarbon fractions in PCBs. A consensus from a wide array of characterization techniques utilized herein (ICP-OES, IC, XRD, FTIR, SEM-EDX, and TGA) clearly demonstrates the transformation of alumina upon its co-pyrolysis with the non-metallic fractions of PCBs, into aluminum bromides and oxy-bromides. ICP-OES measurements disclose the presence of high concentration of Cu in the non-metallic fraction of PCB, along with minor levels of selected valuable metals. Likewise, elemental ionic analysis by IC demonstrates an elevated concentration of bromine in washed alumina-PCBs pyrolysates, especially at 500 °C. The Coats-Redfern model facilitates the derivation of thermo-kinetic parameters underpinning the thermal degradation of alumina-PCB mixtures. Density functional theory calculations (DFT) establish an accessible reaction pathway for the HBr uptake by the alumina surface, thus elucidating chemical reactions governing the observed alumina debromination activity. Findings from this study illustrate the capacity of alumina as a HBr fixation agent during the thermal treatment of e-waste.

In recent years, metal–organic frameworks (MOFs) have emerged as a promising support for immobilizing enzymes due to their high designability and structural diversity. Previous studies show that MOFs with single-crystal-ordered macroporous structures can effectively improve the accessibility of large-size enzyme and reduce the mass transfer resistance compared to conventional MOFs. In order to further enhance the reusability of lipase immobilized on macroporous MOFs, modification of MOFs through some magnetic particles could be an efficient approach. In this work, magnetic macroporous zeolitic imidazolate framework-8 (ZIF-8), referred to as m-M-ZIF-8 (with an average macropore size of about 140 nm), was synthesized and used for the immobilization of Thermomyces lanuginosus lipase (TLL). It was found that enzyme loading and the specific enzyme activity of the immobilized lipase were greatly enhanced through this magnetic modification. The enzyme loading of TLL@C-ZIF-8, T LL@M-ZIF-8, and TLL@m-M-ZIF-8 was 0.060, 0.074, and 0.076 mg/mg respectively. Besides, the activity of 93.5% was maintained after the immobilized lipase being repeatedly used for five batches, which was much higher than that of the immobilized lipase without magnetic modification, which was only 73.4%.

Immobilization has been proposed as a way to simplify the separation and repeated reuse of enzymes, which is essential for their feasible application at industrial scales. However, in their immobilized form, enzyme activity is fully utilized, due primarily to the additional diffusion limitations. Here, the immobilization of lipase on zeolite and its use in catalyzing oil hydrolysis is studied. Adsorption isotherms were investigated, and the data identified the model that best describes the process, which is the Sips model. The adsorption capacity of zeolite was determined as 62.6 mg/g, which is relatively high due to the high porosity of the support. The rate of enzymatic hydrolysis of olive oil, using the immobilized lipase, was determined at a pH of 7 and a temperature of 40 °C and was compared to that when using free enzymes. The results determined the parameters for a diffusion-reaction model. The effects of both the surface reaction and diffusion were found to be significant, with a slightly higher effect from surface reactions.

The effect of the exposure to thermo-switchable solvent (TSS) on cell wall disruption of Chlorella sp. microalgae was investigated. The combustion and kinetic behaviors of microalgae cells treated with TSS, which was maintained at its hydrophilic state for 1.5 h to disrupt the cell wall, were analyzed and compared with those of undisrupted cells. The X-ray diffraction (XRD) results showed a clear drop in the crystallinity of the TSS-treated samples, which was mainly due to the degradation of the cellulosic material. The results were confirmed from the thermogravimetric analysis, which showed a drop in the cellulosic material from 71.9% in the untreated sample to 49% for TSS-treated sample. The activation energy of TSS-treated sample from different non-isothermal models was 44.90–157.97 (FWO), 103.09–492.19 (KAS), and 100.60–478.89 kJ mol−1 (Starink). The values were lower at low conversions (x ≤ 0.5) than untreated samples whose activation energy was 70.67–152.98 (FWO), 195.38–465.58 (KAS), and 190.39–453.11 kJ mol−1 (Starink). The low activation energies for all models of TSS-treated samples indicate that less energy would be required for the thermal conversion processes, as compared with the untreated samples. The tested model-free methods reduce mass transfer limitations, with Flynn-Wall-Ozawa (FWO) compensating for experimental errors, whereas Kissinger-Akahira-Sunose (KAS) and Starink for providing precision to kinetic data depending on a good constant degree of conversion. The reaction mechanism was represented well by the Malek and Popescu. The results presented in this work provide deeper understanding of the effect of TSS on microalgae cell wall disruption.

Phenolic compounds, which are present in considerable amounts in industrial wastewater, are toxic, even at low concentrations. Most bacteria used in conventional treatment methods for the removal of phenolics are pathogenic, and their biomass does not have an evident commercial value. We evaluated the usability of microalgae for the removal of phenolic compounds from simulated wastewater and as a sustainable oil source for biodiesel production with the aim to render microalgae cultivation more economically attractive. Freshwater and marine microalgae species, Chlorella sp. and Tetraselmis sp., were used to remove phenol, 4-nitrophenol, and 2,4-dinitrophenol, which are commonly found in refinery wastewater. The effect of initial phenolics concentrations on biomass growth and phenolics removal was evaluated and kinetics models were developed to describe the systems. Freshwater Chlorella sp. was grown in a pilot-scale open pond with optimum phenolics concentrations, and oil extracted from the harvested biomass was used to produce biodiesel using an in-house heterogeneous alkaline catalyst. The effects of catalyst amount, methanol:oil molar ratio, and reaction temperature on biodiesel production were determined after 4 h of reaction. The experimental data were used to determine the kinetics parameters of the reaction, and to develop a second-order interactive model that was used to determine the significance of the above parameters and to optimize the process. The optimum conditions were found to be a catalyst wt% of 7.7, methanol:oil molar ratio of 12, and temperature of 45 °C, at which the biodiesel after 4 h was 30.4%.

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. Keywords: Biodiesel, Microalgae, Supercritical CO2, Extraction, Transesterification

The depletion of fossil fuel resources and the negative impact of their use on the climate have resulted in the need for alternative sources of clean, sustainable energy. One available alternative, bioethanol, is a potential substitute for, or additive to, petroleum-derived gasoline. In the lignocellulose-to-bioethanol process, the cellulose hydrolysis step represents a major hurdle that hinders commercialization. To achieve economical production of bioethanol from lignocellulosic materials, the rate and yield of the enzymatic hydrolysis of cellulose, which is preferred over other chemically catalyzed processes, must be enhanced. To achieve this, product inhibition and enzyme loss, which are two major challenges, must be overcome. The implementation of membranes, which can permeate molecules selectively based on their size, offers a solution to this problem. Membrane bioreactors (MBRs) can enhance enzymatic hydrolysis yields and lower costs by retaining enzymes for repeated usage while permeating the products. This paper presents a critical discussion of the use of MBRs as a promising approach to the enhanced enzymatic hydrolysis of cellulosic materials. Various MBR configurations and factors that affect their performance are presented.

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.

Immobilization of enzyme on metal-organic frameworks (MOFs) has drawn increasing interest owing to their many well-recognized characteristics. However, the pore sizes of MOFs (mostly micropores and mesopores) limit their application for enzyme immobilization to a great extent owing to the large size of enzyme molecules. Synthesis of MOFs with macropores would therefore solve this problem, typically encountered with conventional MOFs. In this work, macroporous zeolitic imidazolate frameworks (ZIF-8), referred to as M-ZIF-8, were synthesized and used for immobilization of Aspergillus niger lipase (ANL). Immobilization efficiency using M-ZIF-8 and enzymatic catalytic performance for biodiesel preparation were investigated. The immobilized ANL on M-ZIF-8 (ANL@M-ZIF-8) showed higher enzymatic activity (6.5-fold), activity recovery (3.8-fold), thermal stability (1.4- and 3.4-fold at 80 and 100 °C, respectively), reusability (after five cycles, 68% of initial activity was maintained), and porosity than ANL on conventional ZIF-8 (ANL/ZIF-8). In addition, by using ANL@M-ZIF-8 for catalyzing a biodiesel production reaction, a higher fatty acid methyl ester yield was achieved.

Hydrogenation of carbon dioxide (CO2) to formic acid by the enzyme formate dehydrogenase (FDH) is a promising technology for reducing CO2 concentrations in an environmentally friendly manner. However, the easy separation of FDH with enhanced stability and reusability is essential to the practical and economical implementation of the process. To achieve this, the enzyme must be used in an immobilized form. However, conventional immobilization by physical adsorption is prone to leaching, resulting in low stability. Although other immobilization methods (such as chemical adsorption) enhance stability, they generally result in low activity. In addition, mass transfer limitations are a major problem with most conventional immobilized enzymes. In this review paper, the effectiveness of metal organic frameworks (MOFs) is assessed as a promising alternative support for FDH immobilization. Kinetic mechanisms and stability of wild FDH from various sources were assessed and compared to those of cloned and genetically modified FDH. Various techniques for the synthesis of MOFs and different immobilization strategies are presented, with special emphasis on in situ and post synthetic immobilization of FDH in MOFs for CO2 hydrogenation.

Background In recent years, microalgae (MA) have attracted much interest considering their possible therapeutic application. They contain active natural compounds or derivatives (extracts, pure or chemically modified compounds) that have increasing applications in the pharmaceutical industry. Methods The present study aims to examine microalgae for new photosensitizers, with a potential to be used in the light-associated treatment of tumors. Semi-purified extracts of several microalgae strains were evaluated as photosensitizers for photodynamic therapy (PDT) applications. Four tumor cell lines (A549, LNCap, MCF-7, and MDA-MB 435) were used to assess 34 samples extracted by three methods: cellulase enzyme, lysozyme enzyme and ultra-sonication. The fluorescence measurements and the recorded images alongside the spectral intensities between 650–800 nm wavelengths provided characteristic features to some of the contents of the examined extracts. Results Several microalgae constituents activated by blue light (BL), red light (RL) or both (in sequence) exhibited significant effects on the viability of the tumor cell lines, decreasing it as much as 95% for certain MA constituents. Majority of the MA constituents showed a higher phototoxicity after exposure to both blue and red lights than the photo-induced toxicity when exposed to a single light source. The viability of the tumor cells exhibited the dose dependent response with the MA constituents. Conclusion The results clearly showed that MA constituents are potential photosensitizers that have a significant photo-damage effects on the tested cancer cells.

Solvay process is an efficient treatment technique for reject brine from desalination, where salinity is reduced by removing Na+ by adding NH3 . However, in this process large amounts of NH3 are consumed and Cl– ions are not affected. Electrocoagulation has been tested for removing Cl– and NH3 regeneration. When no current was applied, removal of the ions was insignificant. Applying a current density of 0.1167 A/cm2 increased the removal percentages of NH4+ and Cl– by 71.6% and 26.9%, respectively, which proved that the removal was due to electrocoagulation. It was found that the removal percentages and rates increased with increasing the current density and temperature but decreased as the initial ion concentration increased. Three-experiment design levels and response surface methodologies were used to model the system. A second-order polynomial model was developed and used to predict the optimum conditions, which were found to be at a 0.2 A/cm2 current density, 36.8°C temperature, and initial Cl− concentration of 7.4 × 103mg/L. The accuracy of the model was verified against an independent run, not used in the development of the model, and the error did not exceed 10% for both ions Scopus

Switchable solvents with hydrophobicities that can be reversibly changed were evaluated as single solvents for oil extraction from wet biomass. Three switchable solvents, N,N-dimethylcyclohexylamine (DMCHA), N-ethylbutylamine (EBA), and dipropylamine, were used to extract oil from the undisrupted wet paste of harvested Chlorella sp. microalgae. The oil extraction yields for the three solvents were 13.6%, 12.3%, and 7.0%, respectively. However, single hydrophobicity solvents n-hexane and [Bmim][PF6] were unable to extract any oil, achieving yields of 0% and 0.7%, respectively. A parametric study was performed to evaluate the effects of temperature, cell disruption duration, and extraction duration on the effectiveness of oil extraction. The results were used to develop a statistical model to predict oil extraction effectiveness under different conditions. The switchable solvents were also evaluated in simultaneous extraction-reaction systems used to convert the oils extracted from wet microalgae into biodiesel. The use of enzymes was found to enhance the production yield of biodiesel by 33%. The highest biodiesel yield of 47.5% was achieved using DMCHA at 35 °C with a methanol/oil molar ratio of 6:1 and a 30% enzyme loading employing a solvent program comprising 1-h cell disruption, 1-h extraction/reaction, and 1-h phase separation steps. The proposed strategy of using a single solvent for simultaneous extraction and reaction could substantially simplify biodiesel production from wet microalgae.

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.

Microalgae is considered the most promising source of oils for biodiesel production. Beside microalgae contain proteins and pigments, which have large applications in the food and pharmaceutical industries. Combining the cultivation of microalgae for the production of these compounds with wastewater treatment renders the overall process very attractive and economically feasible. However, the selection of the most suitable application to be coupled with the wastewater treatment depends on the composition of the harvested microalgae. In the present work, the effectiveness of Chlorella sp. for the degradation of p-cresol have been evaluated at a concentration ranging from 35 to 330 mg/L. The effect of initial concentration on the contaminants removal, biomass productivity and the chemical composition of microalgae has been determined. Results shows that, Chlorella sp. can degrade p-cresol at concentration up to 330 mg/L, and use it for biomass growth. Biochemical assay showed an improvement in the lipid productivity at higher concentrations, combined with the reduction in the protein content. The highest pigment composition was obtained at the optimum biomass growth, at 150 mg/L. These results give deep understanding of the factors that must be considered when integrating wastewater treatment with using the harvested biomass in other applications.

Ionic liquids (ILs) have been proposed as a more benign replacement to toxic and volatile organic solvents in enzymatic biodiesel production, used to minimize methanol inhibition effect and enhance the stability of immobilized enzyme. Despite their several advantages, ILs are expensive, which renders the overall process unfeasible. In this work, the use of low-cost deep eutectic solvents (DESs) has been investigated as a new reaction medium for enzymatic biodiesel production from waste oils. A DES composed of chlorine-chloride and glycerol (ChCl:Gly) was tested and its effectiveness was compared to 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], which has shown positive results. To decrease the viscosity of ChCl:Gly DES, ternary ChCl:Gly:water DESs with different water contents were prepared and tested. Despite lower cost compared to ILs, without successful repeated reuse of the DES-immobilized lipase system, their advantages remain theoretical. Therefore, the reusability of the DES-Novozym®435 system in consecutive cycles was examined. It was shown that 34% biodiesel production yield could be achieved in ChCl:Gly at 1:2 molar ratio, compared to 23% when [bmim][PF6] was used. The yield increased further, when the ternary DES of ChCl:Gly:water (1:2) with 3 wt% water was used, reaching 44%. By removing the by-product glycerol, the reusability of the DES-immobilized system was improved, with better results achieved using 1-butanol compared to using ethylene glycol. Keywords: Biodiesel, Deep eutectic solvent, Ionic liquids, Immobilized lipase, Reusability

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.

Betty Titus Mathew,1 Shaima Raji,2 Sawsan Dagher,1 Ali Hilal-Alnaqbi,1,3 Abdel-Hamid Ismail Mourad,1,4 Sulaiman Al-Zuhair,5 Mahmoud Al Ahmad,2 Khaled Abbas El-Tarabily,6 Amr Amin6,7 1Mechanical Engineering Department, College of Engineering, United Arab Emirates University, Al Ain, United Arab Emirates; 2Electrical Engineering Department, College of Engineering, United Arab Emirates University, Al Ain, United Arab Emirates; 3Abu Dhabi Polytechnic, Abu Dhabi, United Arab Emirates; 4Mechanical Design Department, Faculty of Engineering, Helwan University, Helwan, Cairo, Egypt; 5Chemical Engineering Department, College of Engineering, United Arab Emirates University, Al Ain, United Arab Emirates; 6Biology Department, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates; 7Department of Zoology/College of Science, Cairo University, Giza, Egypt Background: Activated carbon (AC) is a common adsorbent that is used in both artificial and bioartificial liver devices.Methods: Three natural materials – date pits of Phoenix dactylifera (fruit), Simmondsia chinensis (jojoba) seeds, and Scenedesmus 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.Results: 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 date-pit AC as the best to preserve liver cell integrity.Conclusion: The findings of this study introduce date-pit-based AC as a novel alternative biomaterial for the removal of protein-bound toxins in bioartificial liver devices. Keywords: activated carbon, adsorption, cytotoxicity, phytomaterials, in vitro analysis, 3D cultures, 2D cultures

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.

Lipase has successfully been encapsulated into hexagonal zeolitic imidazolate frameworks (ZIF-8) for use in biodiesel production. It was shown that the lipase encapsulation did not have a significant effect on the morphology, surface properties and crystallinity. The effects of methanol ratio, temperature, oil concentration and water content, on the biodiesel production yield and rate of reaction, were tested. The highest yield was obtained at a methanol ratio and temperature of 6:1 and 40 °C, respectively, and a drop was observed by increasing both. It was also shown that the yield decreased with the increase in water content. The activity and stability of the immobilized lipase in ZIF-8 by encapsulation was compared to that immobilized by surface adsorption. Although the adsorbed lipase on ZIF-8 showed higher activity, the stability of the encapsulated one was higher. At methanol ratio of 12:1, the encapsulated lipase in ZIF-8 maintained 83% residual activity after 5 cycles, compared to only 34% attained by the adsorbed lipase at the same conditions. The experimental results were used to determine the kinetics parameters of modified Ping Pong Bi Bi model, and the accuracy of the prediction were compared to those obtained by the Michaelis Menten model. To gain a better insight into how the reaction occurs inside the ZIF-8 crystal with encapsulated lipase, a diffusion–reaction model was developed and numerically solved. The results clearly show that the substrate did not diffuse deeply into the crystal, which further confirmed the mass transfer limitation that resulted in the lower activity of the encapsulated lipase as compared to the adsorbed one. The developed numerical model can be applied to any diffusion–reaction systems.

Treatment of municipal wastewater, which involves multiple steps, produces large amounts of biosolid 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 biosolid 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 biosolid 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 increase with the increase in the acidic strength. The highest extracted gold yield was 0.012 mg/g of biomass. The amount of gold recovery into the TBP solution was 26%, which was much higher than that of other metals extracted into the acid solution. The importance of removing the metals from the biosolid is obvious, as it allows the latter to be used as a fertilizer. In addition, using only one additional step, a valuable product, gold, can be selectively separated, despite being present in lower amounts that other metals found in the sludge.

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.

Bioethanol production from lignocellulosic biomass depends on enzymatic cellulose hydrolysis to generate glucose. However, enzyme inhibition by the product is one of the several problems making lignocelluloses refractory to this process. To resolve this, we designed a membrane bioreactor (MBR) with an inverted dead-end filtration concept for simultaneous removal of the product during the reaction. Polyethersulfone membranes were used, and their selectivity in allowing only product permeation was proven. The effects of different water fluxes and initial substrate concentrations were investigated. Additionally, a detailed kinetic model based on the mechanistic steps was developed to predict the dynamic behavior of the system, and the kinetic parameters were estimated by fitting the experimental data. The MBR yield increased from 7% without product separation to 45% with product separation. Both kinetic and statistical models showed good agreement (R2: 0.96 and 0.97, respectively). According to the statistical model, the optimal conditions were a substrate concentration of 2.67 g/L and a water flux of 0.8 mL/min, which achieves a maximum yield of 86.7%. Our novel MBR and kinetic model allow for a better understanding of the dynamic behavior of this important reaction–diffusion system and can be used to predict, design, and optimize similar MBRs.

Background: 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. Methods: 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 agents on the human BPH-1 cell line (benign human prostate epithelial cells). The t-test was used to statistically analyze the results and determine the significance. Results: Against LNCap and A549 cells, the performance of cellulase-treated extracts was better (with p-values 0.05, as compared to the control); however, they had similar effects against the other two tumor cell lines (with p-values mainly < 0.05, as compared to the control). Moreover, based on their effect on BPH-1 cells, extracts from lysozyme-treated MA cells were determined to be safer against the benign prostate hyperplasia cells, BPH-1 (with p-values mainly > 0.05, as compared to the control). After dialysis, the performance of MA extracts from lysozyme-treated cells was enhanced significantly (with p-values dropping to < 0.05, as compared to the control). Conclusions: The results of this work provide important information and could provide the foundation for further research to incorporate MA constituents into pharmaceutical anti-cancer therapeutic formulations.

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 t...

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 enzymes or ILs. The available literature clearly indicates that MOFs are the most suitable immobilization supports, leading to higher biodiesel production without affecting the catalytic activity while increasing the catalyst stability and reusability in several cycles.

Biodiesel production had received a considerable attention as a green, non-toxic and renewable alternative to petroleum diesel. To avoid using vegetable oils, which are expensive and compete with food, as feedstock, waste oils have been proposed. However, these waste materials contain a large amount of free fatty acids that complicates the production process. In this work, biodiesel production using an alternative feedstock; namely oils from date-pits, has been investigated. These oils have the same favorable features of straight oils, and at the same time are considered waste, since they are extracted from a waste material. The yield of oils extracted using n-hexane in a Soxhlet apparatus was compared to that of oils extracted using methanol-chloroform solvent mixture. The extracted oils were then converted to biodiesel via transesterification with methanol in presence of Novozym&#174435 or Eversa&#174Transform. The highest oils extraction yield of 11.7%, per dry weight sample, was obtained using Soxhlet extraction apparatus compared to 8.9% using methanol-chloroform mixture. The highest biodiesel production yield was 30% of the oil used, achieved after 6 hours using Novozym&#174435 at 40°C, 5:1 methanol to oil molar ratio and 10wt% enzyme loading. By using a chemical alkaline catalyst, NaOH, at the same conditions, the yield was 27%.

Microalgae are considered a promising source of oil for biodiesel production. This work reports an estimation method of oil content inside living microalgal cells by visualization and image processing techniques. This approach was used to analyze the time course of oil accumulation patterns in Nile Red-stained microalgal cells of Scenedesmus sp. cultivated in nitrogen-deficient medium used to induce oil accumulation in microalgal cells. Nile Red staining is a widely used technique for studying oil content of microalgal cells. The intracellular oil content was estimated by mathematically evaluating the oil volume inside the stained cell. This novel visualization approach has the potential to be used in ex vivo studies of oil content at the level of single microalgal cells. This method can also be applied to other types of oil-producing microorganisms because of its accuracy, precision, and reduction in the time and effort required for optimization.

Biodiesel produced from oil-rich feedstocks is known as a green replacement for conventional petroleum diesel. Transesterification is the common method used for biodiesel production. The enzymatic biodiesel production, using lipases, has recently been receiving extensive attention, due to its advantages over conventional alkali catalyzed process. The lipases can work at mild operating conditions, thus requiring less energy, with the ability to catalyze both triglycerides and free fatty acids (FFAs) from different oil sources, requiring fewer post-production steps. Among the process challenges that face this process is the inhibition of the lipase with excessive use of alcohols, resulting in a decrease in biodiesel yield. The use of organic solvents, as a reaction medium, becomes essential in this case. However, most organic solvents are toxic and volatile with harmful impacts on the environmental. In addition, with the use of volatile organic solvents, an additional unit is required to separate them from the products, for the purification of the product and recycling of the solvent. In this paper, the prospect of using alternative solvents, specifically supercritical carbon dioxide (SC-CO2) and ionic liquids (ILs), in enzymatic biodiesel production is presented. The properties of these alternative solvents, their advantages over organic solvents, factors affecting lipases activity and stability in these solvents, and the challenges facing process commercialization are discussed. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Steam reforming of commercially available LPG using Ru/Al2O3 and Ni/Al2O3 catalysts has been studied at temperatures between 573 and 773 K. Ru/Al2O3 catalyst showed higher rates of reaction and lower activation energies of the three main components of LPG, compared with Ni/Al2O3. However, Ni/Al2O3 catalyst showed a better H2:CH4 selectivity. The activation energy of n-butane was the lowest over Ru/Al2O3, whereas over Ni/Al2O3, propane had the lowest activation energy. The activation energy of i-butane was always the highest over both catalysts, which suggests that both catalysts performed better with unbranched molecules. A slight increase in activation energy was observed, when each component of the LPG mixture was studied separately as a pure gas, compared with being mixed in LPG. At a constant temperature of 773 K, hydrogen production yield and H2:CH4 selectivity were determined using Ru/Al2O3 at different steam:carbon (S:C) ratios and LPG flow rates. It was found that the yield and selectivity increas...

Crude proteins and pigments were extracted from different microalgae strains, both marine and freshwater. The effectiveness of enzymatic pre‐treatment prior to protein extraction was evaluated and compared to conventional techniques, including ultrasonication and high‐pressure water extraction. Enzymatic pre‐treatment was chosen as it could be carried out at mild shear conditions and does not subject the proteins to high temperatures, as with the ultrasonication approach. Using enzymatic pre‐treatment, the extracted proteins yields of all tested microalgae strains were approximately 0.7 mg per mg of dry cell weight. These values were comparable to those achieved using a commercial lytic kit. Ultrasonication was not very effective for proteins extraction from Chlorella sp., and the extracted proteins yields did not exceed 0.4 mg per mg of dry cell weight. For other strains, similar yields were achieved by both treatment methods. The time‐course effect of enzymatic incubation on the proteins extraction efficiency was more evident using laccase compared to lysozyme, which suggested that the former enzyme has a slower rate of cell disruption. The crude extracted proteins were fractionated using an ion exchange resin and were analyzed by the electrophoresis technique. They were further tested for their antioxidant activity, the highest of which was about 60% from Nannochloropsis sp. The total phenolic contents in the selected strains were also determined, with Chlorella sp. showing the highest content reaching 17 mg/g. Lysozyme was also found to enhance the extraction of pigments, with Chlorella sp. showing the highest pigments contents of 16.02, 4.59 and 5.22 mg/g of chlorophyll a, chlorophyll b and total carotenoids, respectively.

The ability of three freshwater microalgae strains, namely Chlorella sp. , Pseudochlorococcum sp . and Chlamydomonas sp. to grow in water containing different concentrations of phenol has been tested. The effectiveness of the selected strains to utilize the phenol as a carbon source and reduce its concentration has also been assessed. The phenol removal efficiency and cells growth rates were evaluated at different initial phenol concentrations, in the range of 100-450 ppm. It was found that growing, under a reduced illumination condition, increased the inhibition onset concentration, enhanced the phenol removal and allowed the strains to tolerate higher phenol concentrations reaching 450 ppm. In the tested range of the phenol concentrations, Chlamydomonas sp . has shown to have the highest specific growth rate of 0.59 day -1 , whereas Pseudochlorococcum sp showed the highest phenol removal rate of 166 ppm day -1 . Three kinetics models that incorporate substrate inhibition were tested to describe the growth, which show almost identical fittings.

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 supports for various enzymes suggest that CGTase could be immobilized for enhanced production of CDs. The three-dimensional microenvironment of MOFs could maintain the stability of CGTase while posing minimal diffusional limitations. Moreover, the presence of different functional groups on the surfaces of MOFs could provide multiple points for attachment of CGTase, thereby reducing enzyme loss through leaching. The present review focuses on the advantages MOFs can offer as support for CGTase immobilization as well as their potential for application in CD production.

The growing demand for dates, as food, has enhanced its production and increased the total amount of date pits waste. Subcritical water extraction (SCWE) can be used to effectively extract valuable products from date pits. This study was to extract phenolic compounds, total flavonoid content, antioxidants, and dietary fibres from the date seeds using SCWE. The effects of process variables such as feed mixture concentration (x), extraction temperature (T), and extraction time (t) on the yields of total phenolic content (TPC), total flavonoid content (TFC), antioxidants, and dietary fibres were investigated for process optimisation using desirability approach. The results showed that extraction temperature could significantly increase TPC, TFC, and dietary fibres extraction yields, but has less effect on the antioxidant extraction. The feed mixture concentration has shown a significant effect on antioxidant extraction but was insignificant on TPC, TFC, and dietary fibres extractions. The desirability approach of process optimisation validated the feasibility of using SCWE for valuable products extraction from date pits.

The seeds of a local date palm cultivar from the United Arab Emirates, Allig, were characterized in this study. Soxhlet, Folch, and CO2 supercritical extraction were employed to obtain oil from Allig date seed (DS) powder composed of 0.1–0.3 mm particles, yielding oil extraction yield percentages of 10.2%, 9.5%, and 9.8%, respectively. The main fatty acid in the extracted oil was saturated stearic acid, comprising 47.9% of the total fatty acid content. After oil extraction, the total metal content in the DSs dropped from 3.2% to 2.8%, suggesting that some metals were extracted with the oil. On the other hand, the average heating value of the DSs increased from 28.55 ± 1.84 to 29.63 ± 1.28 MJ/kg after oil extraction. The average percentages of dehydration moisture, devitalization protein and carbohydrates, devitalization lipids, and solid decomposition in the DSs before oil extraction were 1–2%, 50–55%, 10–15%, and 30–35%, respectively, whereas those for the DSs after oil extraction were 20–25%, 35–30%, 0%, and 35–40%, respectively. As expected, the lipid content dropped after oil extraction. The heat of combustion and extracted oil results indicate that palm DSs, with their relatively high energy densities, have potential as a source of energy, among other notable organic products.

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&rsquo, 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 analysis and propose cost-effective trade-offs. These will aid the consultants and contractors in choosing appropriate green building regulations in the UAE by highlighting the potential of each parameter within green building regulations in terms of energy, water, and economic performance.

A thermo-responsive switchable solvent (TSS), which switched hydrophobicity by the change in temperature, was successfully used for simultaneous cell disruption, oil extraction-reaction, and biodiesel separation from wet microalgae. Catalyzed by immobilized lipase, the entire process was carried out in a single pot using the same solvent without drying the microalgae. Besides being easier to operate, the biodiesel yield using the TSS was 21% higher than that achieved using CO2-triggered switchable solvent under the same conditions and solvent switching program. To optimize the process, a parametric study was performed to evaluate the effects of cell disruption and extraction/reaction durations and methanol amount on the biodiesel production yield. The results were used to develop a statistical model to predict the biodiesel yield under different conditions. The model was validated by repeating the reaction as defined by the model and a yield of 75.11 ± 1.03% was observed. Moreover, we observed that the immobilized enzyme retained its activity till two rounds of reaction, and future optimization may improve the reusability further. In conclusion, our results showed that the successful use of a TSS lipids extraction-reaction from wet biomass can significantly simplify the biodiesel production from wet microalgae.