Maximum Conversion Yield Research Articles

Valorization of slaughterhouse wastes through transesterification for sustainable biodiesel production using potassium hydroxide as a heterogeneous catalyst

In this research, biodiesel was synthesized from chicken gizzard using potassium hydroxide catalyst and the effects of operating parameters including catalyst weight percentage (0.005–0.015%), methanol to oil molar ratio (3:1 to 9:1), temperature (50–70 °C), contact time (4–6 h), and stirring rate (400–600 rpm) on the methyl ester conversion yield were investigated. This study is innovative as it explores the transesterification of chicken gizzard, a low-cost feedstock, which has not yet been investigated. Furthermore, the applied catalyst was characterized through BET, FTIR, FSEM, XRD, XRF, EDS/Map techniques, while GC analysis showed that heptanoeic acid (41.57%), arachidic acid (27.63%), and linoleic acid (15.48%) constituted the main constituents of the extracted oil. Based on BET analysis the specific surface area of the used catalyst was 358 m2 g−1 which is an appropriate value for the current purpose. The results revealed that the maximum biodiesel conversion yield (94%) was obtained under the optimal conditions of catalyst weight percentage at %0.01, methanol to oil ratio at a ratio of 6:1, temperature at 60 °C, reaction duration of 5 h, and stirring rate at 500 rpm. The regeneration studies demonstrated that the used catalyst can be used for 2 consecutive cycles with acceptable conversion yields. However, beyond this point, the yield deteriorates, dropping to below 90%. Furthermore, the comparison of the physical characteristics of the generated biodiesel, including density, viscosity, flame point, cloud point, pour point, aniline point, cetane number, and copper strip corrosion with ASTM-D675110 and EN-14214 standards showed that they were within the standards ranges which indicates that the produced biodiesel was a viable alternative to traditional diesel fuel. Considering the promising results obtained from biodiesel production utilizing chicken gizzard for the first time, this waste material can be deemed a cost-effective raw material for biodiesel production.

Agro-industrial residue of Pouteria sapota peels as a green heterogeneous catalyst to produce biodiesel from soybean and sunflower oils

We report the use of ash from the agro-industrial waste of Pouteria sapota peels as a reusable heterogeneous catalyst to produce biodiesel from soybean and sunflower oils. The heterogeneous catalyst was prepared by activating raw Pouteria sapota peel powder at 500 °C for 2 h. The physicochemical and structural properties of the ash were evaluated by SEM-EDS, XRD, FTIR, BET analyses, and its basicity was determined through acid-base titration. The good activity of the ash-based catalyst was attributed mainly to the presence of potassium chloride (KCl), a specific surface area of 1.432 m2 g−1, and its high basicity of 9.069 mmol g−1. A maximum conversion yield of 92% was achieved for both the oils under optimized reaction conditions. For the soybean and sunflower oils, the optimum parameters were 3 wt% and 5 wt% of catalyst charge, methanol to oil molar ratio of 6:1 and 9:1, and a reaction time of 240 min, respectively. The reactions were performed at 65 °C under stirring at 400 rpm. The physicochemical properties of soybean and sunflower biodiesel satisfactorily complied with the International Standard of the American Society for Testing and Materials (ASTM-D6751) and the European Standardization (EN-14214).

Expression and characterization of an organic solvent tolerant recombinant lipase from Staphylococcus capitis SH6 for food wastewater treatment

The study illustrated here aims on an organic solvent tolerant lipase from Staphylococcus capitis (SCL). The gene part, encoding the mature lipase, was cloned and sequenced. The concluded polypeptide sequence, equivalent to the protein, consist of 388 amino acid residues with a molecular mass of about 45 kDa. A structure-based alignment of the SCL amino acid sequence shows high identities with those many staphylococcal lipases. From this alignment of sequences, the catalytic triad (Ser 117, Asp 308 and His 347) of SCL could be identified. The mature part of the SCL was expressed in Escherichia coli and the recombinant lipase (r-SCL) was purified to homogeneity. The purified r-SCL presented a quite interesting stability at low temperatures (< 30 °C) and the enzyme was found to be highly stable in polar organic solvent and at a pH ranging from 3 to 12. After that, we have demonstrated that the recombinant enzyme may be implicated in the biodegradability of oily wastewater from effluents of fast-food restaurants; the maximum conversion yield into fatty acids obtained at 30 °C, was 65%.

Microalgae to Bioenergy: Optimization of Aurantiochytrium sp. Saccharification.

Microalgae are a promising feedstock for bioethanol production, essentially due to their high growth rates and absence of lignin. Hydrolysis-where the monosaccharides are released for further fermentation-is considered a critical step, and its optimization is advised for each raw material. The present study focuses on the thermal acid hydrolysis (with sulfuric acid) of Aurantiochytrium sp. through a response surface methodology (RSM), studying the effect of acid concentration, hydrolysis time and biomass/acid ratio on both sugar concentration of the hydrolysate and biomass conversion yield. Preliminary studies allowed to establish the range of the variables to be optimized. The obtained models predicted a maximum sugar concentration (18.05 g/L; R2 = 0.990) after 90 min of hydrolysis, using 15% (w/v) biomass/acid ratio and sulfuric acid at 3.5% (v/v), whereas the maximum conversion yield (12.86 g/100 g; R2 = 0.876) was obtained using 9.3% (w/v) biomass/acid ratio, maintaining the other parameters. Model outputs indicate that the biomass/acid ratio and time are the most influential parameters on the sugar concentration and yield models, respectively. The study allowed to obtain a predictive model that is very well adjusted to the experimental data to find the best saccharification conditions for the Aurantiochytrium sp. microalgae.

Hydrogen Production from Catalytic Pyrolysis of Phenol as Tar Model Compound in Magnetic Field

Tar conversion during biomass pyrolysis is essential for hydrogen production. In this study, phenol and 10 wt.% Ni/CaO-Ca12Al14O33 were used as the tar model compound and catalyst, respectively. The purpose of the present investigation was to analyze the influence of varying magnetic field strength (ranging from 0 to 80 mT), reaction temperature (ranging from 550 to 700 °C), and carrier gas velocity (ranging from 20 to 30 mL/min) on the catalytic pyrolysis outcomes obtained from phenol. The findings indicated that the conversion rate of phenol and H2 output exhibited an increase with an escalation in magnetic field strength and reaction temperature but demonstrated a decrease with an upsurge in the carrier gas velocity. The ideal conditions for achieving the maximum phenol conversion (91%) and H2 yield (458.5 mL/g) were realized by adjusting the temperature to 650 °C, retaining the carrier gas velocity at 20 mL/min, and elevating the magnetic field intensity to 80 mT. These conditions resulted in a considerable increase in phenol conversion and H2 yield by 22.2% and 28.2%, respectively, compared with those achieved without magnetism. According to the kinetic calculations, it was indicated that the inclusion of a magnetic force had a beneficial effect on the catalytic efficacy of 10 wt.% CaO-Ca12Al14O33. Additionally, this magnetic field was observed to lower the activation energy required for the production of H2 when compared with the activation energy required during phenol catalytic pyrolysis. This consequently resulted in an enhancement of the overall efficiency of H2 production.

Optimization of the process variables on biodegradable industrial lubricant basestock synthesis from Jatropha curcas seed oil via response surface methodology

The synthesis of biolubricants from renewable feedstocks is currently gaining attention. Over 95% of the market is comprised of lubricants made from petroleum. Due to their limited biodegradability and high eco-toxicity, lubricants generated from petroleum constitute a significant environmental hazard. As pollution levels increase and oil supplies decline, there is a rising need to develop biobased alternatives. Manufacturing cleaner fuel products will mitigate the negative environmental impact of greenhouse gas emissions, which contribute to global warming. Jatropha curcas seed oil is an efficient renewable feedstock for biolubricant synthesis. This study optimized the process variables on biodegradable lubricant basestock production from J. curcas seed oil. A central composite design was used to maximize the chemical interaction between J. curcas methyl ester and ethylene glycol (EG) as a polyol. A total of 20 experimental runs were done to examine reaction temperature, time, and the ethylene glycol to fatty acid methyl ester (EG-to-FAME) molar ratio. A statistical model indicated that the maximum conversion yield of jatropha biolubricant (JBL) would be 92.48% under the following optimum reaction conditions: 128.95°C, 202.40 min, and ethylene glycol to fatty acid methyl ester (EG-to-FAME) molar ratio of 3.87:1. At these optimum conditions, an average jatropha biolubricant (JBL) yield of 94.12% was achieved under experimental conditions, and this value was well within the range predicted (92.48%) by the model. The quadratic model predicted the biolubricant output (R2 = 0.9919). The synthesized biolubricant met the requirements of Viscosity Grade 46 (ISO VG 46) set by the International Organization for Standardization.

Antioxidant Activity of Andrographolide from Andrographis paniculataleaf and Its Extraction Optimization by using Accelerated Solvent Extraction

Andrographis paniculata is widely used as a medicinal plant in many countries and andrographolide is the major bioactive compound extracted from A. paniculata leaf. This study purposely to optimize statistical andrographolide extraction using the accelerated solvent extraction (ASE) technique. The Box Behnken design (BBD) was chosen to determine the optimum ASE conditions for the extraction temperature (ºC), cycle number, and extraction time (min) to achieve the highest yield of andrographolide. The optimum ASE conditions were identified as: extraction temperature of 60 ºC, using 3 cycles and 5 min extraction time, with maximum conversion yield as high as 335.2 ± 0.2 mg/g determined by High Performance Liquid Chromatography (HPLC) with the squared correlation coefficients (R2) of 0.97. The findings revealed the ASE method significantly enhanced andrographolide extraction and agreed closely with the predicted value at 337.5 mg/g. Andrographolide was isolated by preparative HPLC technique. A. paniculata leaf extract and extracted andrographolide displayed moderate radical scavenging activity in 2, 2−Diphenyl−1−picrylhydrazyl hydrate (DPPH) assay with IC50 of 0.883 ± 1.597 mg/ml and 0.514 ± 0.285 mg/ml respectively as IC50 for ascorbic acid was 0.048 ± 0.004 mg/ml. A. paniculata extract and andrographolide inhibited the tyrosinase enzyme with IC50 of 0.749 ± 0.293 μg/ml and IC50 of 2.441 ± 2.026 μg/ml indicated stronger tyrosinase inhibition abilities than kojic acid, IC50 of 19.985 ± 0.557 μg/ml. These results suggest that A. paniculata leaf extract and andrographolide have greater potential as sources of biochemical compounds that can be used as skin depigmentation solutions.

UV-driven self-repair of cyclobutane pyrimidine dimers in RNA.

Nucleic acids can be damaged by ultraviolet (UV) irradiation, forming structural photolesions such as cyclobutane-pyrimidine-dimers (CPD). In modern organisms, sophisticated enzymes repair CPD lesions in DNA, but to our knowledge, no RNA-specific enzymes exist for CPD repair. Here, we show for the first time that RNA can protect itself from photolesions by an intrinsic UV-induced self-repair mechanism. This mechanism, prior to this study, has exclusively been observed in DNA and is based on charge transfer from CPD-adjacent bases. In a comparative study, we determined the quantum yields of the self-repair of the CPD-containing RNA sequence, GAU = U to GAUU (0.23%), and DNA sequence, d(GAT = T) to d(GATT) (0.44%), upon 285 nm irradiation via UV/Vis spectroscopy and HPLC analysis. After several hours of irradiation, a maximum conversion yield of ∼16% for GAU = U and ∼33% for d(GAT = T) was reached. We examined the dynamics of the intermediate charge transfer (CT) state responsible for the self-repair with ultrafast UV pump - IR probe spectroscopy. In the dinucleotides GA and d(GA), we found comparable quantum yields of the CT state of ∼50% and lifetimes on the order of several hundred picoseconds. Charge transfer in RNA strands might lead to reactions currently not considered in RNA photochemistry and may help understanding RNA damage formation and repair in modern organisms and viruses. On the UV-rich surface of the early Earth, these self-stabilizing mechanisms likely affected the selection of the earliest nucleotide sequences from which the first organisms may have developed.

Comparison of pretreatment effects on sugar release, energy efficiency and the reuse of effluents

The effect of ultrasonic, alkali and acid pretreatments and their combination on saccharification was investigated, and the impact of the liquid fractions, obtained after the enzymatic hydrolysis of pretreated biomasses, on seed germination was evaluated. Mechanical deconstruction of biomass coupled to chemical and/or physical pretreatments was found to enhance the cellulose to glucose conversion yields for both barley and bean straws. The highest conversion yield of 86% was obtained by ultrasonication coupled to alkaline pretreatment of bean straw, corresponding to 171 mg of glucose/g TS. The maximum conversion yield (48 %) for barley straw was obtained with NaOH pretreatment accounting for approximately 140 mg/gTS. The highest energy efficiency was obtained with NaOH pretreatment (1.7 kg glucose /kWh and 1.9 kg glucose /kWh for barley and bean straws respectively). Therefore, NaOH pretreatment appears the most suitable for an efficient release of glucose from the studied biomasses. As for the effect of the liquid fractions of hydrolysis on seed germination, the diluted effluents (3 %) were found to enhance tomato seeds germination, especially in the case of barley straw, by 17–50 %. This work suggests the valorization of liquid fractions and their reuse for agriculture, which is an option to be considered especially in the context of scarce water resources. Finally, the selected pretreatments based on energy efficiency and environmental impact will be developed at pilot and industrial scale for objective to develop a local and regional bioeconomy. • Alkaline and Alkaline combined with US had the highest impact on enzymatic hydrolysis. • Ball milling has further improved the yields of sugars achieved after pretreatments. • Alkaline pretreatment was the most energy efficient for biomass saccharification. • Effluents from pretreatments had no negative effect on tomato seeds germination.

Carbon dioxide hydrogenation to methanol: Process simulation and optimization studies

This work investigates process simulation and optimization as an efficient approach to mitigate global warming using carbon dioxide hydrogenation to methanol. Modeling and simulation of hydrogenation to methanol were studied using Aspen Plus V8. Cu/ZnO/Al2O3 catalyst is used to optimize parameters to enhance the reduction of CO2 to methanol. The effect of temperature, pressure, and the feed flow rate on CO2 conversion and CH3OH yield was reported. Response surface methodology (RSM) is used to analyze the chemical equilibrium of the CH3OH production process to obtain an optimal way of assuring a relatively higher CO2 conversion and CH3OH production rate. It helps to evaluate the optimum temperature, pressure, andH2/CO2 molar ratio to achieve maximum CO2 conversion and CH3OH yield. The impact of conversion and CH3OH yield was evaluated using surface plots. The RSM studies show optimized conditions for conversion and CH3OH yield at a temperature of 210 °C, a pressure of 55 bar, and a H2/CO2 concentration of 1:5. The anticipated CO2 conversion and CH3OH yield were 87.56% and 11.22%, respectively, whereas the simulation gave CO2 conversion of 87.65% and CH3OH yield of 11.39%. The generated quadratic model accurately predicts carbon dioxide conversion to methanol. The applicability of the model to forecast CO2 conversion and CH3OH yield is supported by the agreement between the simulated and expected results. This work can be considered a possible solution to overcome the thermodynamic difficulty by providing a higher CO2 conversion and would be beneficial for further investigation in industrial process.

Spraying Water Microdroplets Containing 1,2,3-Triazole Converts Carbon Dioxide into Formic Acid.

We report the use of 1,2,3-triazole (Tz)-containing water microdroplets for gas-phase carbon dioxide (CO2) reduction at room temperature. Using a coaxial sonic spraying setup, the CO2 can be efficiently captured by Tz and converted to formic acid (HCOOH; FA) at the gas-liquid interface (GLI). A mass spectrometer operated in negative ion mode monitors the capture of CO2 to form the bicarbonate anion (HCO3-) and conversion to form the formate anion (HCOO-). Varied FA species were successfully identified by MS/MS experiments including the formate monomer ([FA - H]-, m/z 45), the dimer ([2FA - H]-, m/z 91; [2FA + Na - 2H]-, m/z 113), the trimer ([3FA - H]-, m/z 137), and some other adducts (such as [FA - H + H2CO3]-, m/z 107; [2FA + Na - 2H + Tz]-, m/z 182). The reaction conditions were systematically optimized to make the maximum conversion yield reach over 80% with an FA concentration of approximately 71 ± 3.1 μM. The mechanism for the reaction is speculated to be that Tz donates the proton and the hydroxide (OH-) at the GLI, resulting in a stepwise yield of electrons to reduce gas-phase CO2 to FA.

Valorization of palm oil via cross-metathesis reaction using 1-octene

The use of palm oil-derived polyol in polyurethane manufacturing is restricted owing to its poor hydroxyl value, which results in a suboptimal polyurethane network. Palm oil could be first chemically modified by cross metathesis (CM) into olefin and ester products with terminal double bonds prior to converting it to the polyols with optimum hydroxyl value. Due to the catalyst degradation and the unwanted self-metathesis reaction, the plant oil CM employing ethylene has been limited by its poor selectivity and low yield. The goal of present research is to investigate the palm oil CM using 1-octene from the aspects of parametric and kinetic analysis. The use of 1-octene was hypothesized to prevent the formation of undesired catalytic intermediates and hence allowing the ruthenium-based Hoveyda Grubbs second generation catalyst (2nd HGC) to maintain its activity and stability. Adopting one factorial at time (OFAT) in a batch system, the effect of different parameters on cross-metathesis of palm oil was examined. The variation in reaction time, temperature, reactant molar ratio of 1-octene to triolein (MOC/TR), and catalyst loadings were correlated to triolein conversion, yield, and selectivity of 1-decene. The products such as 1-decene and glyceryl tri-9-decenoate were quantified using Gas Chromatography-Mass Spectrometry (GC-MS). The maximum triolein conversion and 1-decene yield, 97.78% and 293.36% respectively, were obtained when the cross metathesis of palm oil using 1-octene occurred at 343 K for 2 h with MOC/TR of 8 and catalyst loading of 5 ppm. After three consecutive catalytic tests carried out at best operating condition, the insignificant decline in the reaction performance evidenced that the 2nd HGC catalyst remained active and stable. It was also found that the power-law model well predicted the concentration profile of the cross-metathesis of palm oil using 1-octene, estimating activation energy of 22583 J/mol. This study developed a new technically feasible process for adding value to palm oil, by enabling the use of palm oil as a feedstock for the production of polyol.

Synthesis of Ca–Fe-based heterogeneous catalyst from waste shells and their application for transesterification of Jatropha oil

The depletion of fossil fuel reserves with increased fuel demand and global emissions has increased the search for eco-friendly renewable fuels with a low environmental impact. Biodiesel can be considered as mono-alkyl esters of long-chain fatty acids obtained from the transesterification of vegetable oils and animal fats. Economically low-cost biodiesel production has received considerable interest for blending with fossil-based diesel for a more sustainable future. Therefore, the current study focuses on synthesizing an efficient, low-cost heterogeneous CaO catalyst from waste egg and seashell using a solid-state method and applying it to the transesterification of Jatropha oil. The Ca2Fe2O5 solid catalyst was prepared by doping calcined CaO with iron in a 2:1 ratio using ferric oxide (Fe2O3). Furthermore, the catalyst was extruded and analytically characterized using XRD, FT IR, BET, and its basic strength was quantified by Hammett indicators. Later on, transesterification of Jatropha oil was optimized by varying reaction parameters, such as the molar ratio of methanol to Jatropha oil, reaction time, and catalyst loading. The maximum conversion yield was 96.3% at a 20:1 methanol-to-oil ratio and 80 bar N2 pressure using 5% (w/w) catalyst loading. Furthermore, the catalytic recycling study demonstrated that the Ca2Fe2O5 catalyst could retain > 70–80% of transesterification efficiency and stability up to 4 cycles under high acid value and moisture conditions.Graphical abstract

Enhanced production of biodiesel using nanomaterials: A detailed review on the mechanism and influencing factors

The deterioration of fossil fuel supplies, combined with growing environmental concerns about fossil fuel extraction and consumption, has prompted worldwide communities to focus on renewable energy. Biodiesel production from various biomass feedstock is identified as an environmentally friendly and sustainable alternative. The application of nanomaterials as catalysts in the synthesis of biodiesel has enhanced the yield due to the selectivity. This review article is focused on the applications of potential nanoparticles in biodiesel production and their mechanism of action. The effect of operating variables, namely nanomaterial type, concentration, temperature, methanol to oil ratio, and water content on biodiesel production have been summarized. Under microwave-assisted transesterification, both sodium hydroxide and strontium oxide catalysts, produced highest yield (99%). For calcium oxide nanocatalyst, the highest biodiesel conversion obtained was 98.2% through microwave-assisted transesterification method of waste cooking oil. The optimal conditions for such a high conversion yield were methanol to oil ratio, reaction temperature, time, and catalyst loading of, 1:8, 65 °C, 76 mins, and 4 wt% respectively. The maximum biodiesel conversion yield achieved using KOH nanocatalyst was 96.44% in a microwave-assisted transesterification of waste cotton-seed cooking oil, at optimum conditions of 9.6 min, 0.65 wt% catalyst loading, and 7:1 methanol: oil ratio, respectively. Future perspectives on nanocatalysis for biodiesel production are explained.

Heterogeneous numerical modelling for the auto thermal reforming of crude glycerol in a fixed bed reactor

A mathematical model for the catalytic autothermal reforming (ATR) reaction of synthetic crude glycerol to hydrogen in a fixed bed tubular reactor (FBTR) and over an in-house developed metal oxide catalyst is presented in this work. The heterogeneous model equations account for a two-phase system of solid catalyst and bulk feed gas. Also, the ATR of crude glycerol reaction scheme and intrinsic kinetic rate model over an active, selective, and stable nickel-based catalyst were integrated in the developed model. Also, the model was validated using experimental data generated in our labs for the ATR of synthetic crude glycerol. The modelling results adequately described the detailed gas product composition and distribution, temperature profiles, and conversion propagation in the axial direction of the fixed bed reactor over a wide range of reaction temperature (773–923 K) and mass-time (12.71–158.23 g cat·min·(mol C) −1 ). The crude glycerol conversion predicted with the model showing a close resemblance to those obtained experimentally with an average absolute deviation (AAD) of less than 8%. The maximum crude glycerol conversion and hydrogen yield were found to be 92% and 3 mol hydrogen/mol crude glycerol, respectively. Also, the gas product concentration profile in the reactor was adequately described (90%) accuracy with a hydrogen concentration of 39 vol%.

Multiple-objective optimization in green fuel production via catalytic deoxygenation reaction with NiO-dolomite catalyst

This study investigates the multi-objective optimization of reaction parameters with response surface methodology (RSM) with central composite design (CCD) for the deoxygenation of waste cooking oil (WCO) over low cost-modified local carbonate mineral catalyst (NiO-Malaysian dolomite) into green fuel in the range of gasoline, kerosene and diesel. RSM was performed to study the effect of four operating parameters: temperature (390–430 °C), time (30–120 min), catalyst loading (1–10 wt%) and nitrogen flow rate (50–300 cm3/min). The results indicate that for maximum WCO conversion, deoxygenated oil and product yield, the optimum parameters of the deoxygenation reaction were at 410 °C, 60 min, 5.50 wt% of catalyst loading, and 175 cm3/min of N2. The green fuel properties testing (density, kinematic viscosity, flash point, cloud point, pour point, sulfur, carbon residue, cetane index, oxidation stability, acid value, iodine value and calorific value) and GC–MS analysis show that the product oil meets almost all the requirements of green diesel fuel and hydrocarbon biofuel standards for fuel application while the quadratic model proposed agreed with the experimental data (95% confidence) which indicates that the RSM can adequately predict the reaction products.

Subcritical water pretreatment for agave bagasse fractionation from tequila production and enzymatic susceptibility

This work focuses on the effect of subcritical water pretreatment conditions on agave bagasse chemical composition, biomass fractionation, and enzymatic hydrolysis obtained from the different tequila production processes. The pretreatment was carried out in a batch pressurized reactor within an isothermal regime. The operational conditions for subcritical water pretreatment were (150–190 °C) and (10–50 min). The best operational conditions were selected, based on the increased cellulose content (>50%) in the pretreated solid phase. The conditions for 190 °C for 50 and 30 min of pretreated agave bagasse solids were chosen for enzymatic hydrolysis susceptibility (15 FPU/g of the substrate). The maximum conversion yield (cellulose to glucose) during enzymatic hydrolysis achieved was up to 61.62% (5.86 g/L) in industrial bagasse at 72 h and initial saccharification rate was 0.34 g/(L*h) at 12 h. This study indicates that the agave bagasse is a promising raw material in the development of second-generation biorefineries.

Optimization of an organic solvent-tolerant lipase production by Staphylococcus capitis SH6. Immobilization for biodiesel production and biodegradation of waste greases

Using the statistical approach, this work seeks to optimize the process parameters to boost the generation of an organic solvent-tolerant lipase by Staphylococcus capitis SH6. The main parameters influencing the enzyme production were identified by using Plackett–Burman’s screening design. Among the test variables, only tryptone (25 g/L), malt extract (2.5 g/L), NaCl (10 g/L) and pH (7.0) contributed positively to enzyme production. Then, the crude lipase was immobilized by adsorption on CaCO3 at pH 10. A maximum immobilization efficiency of 82% was obtained by incubating 280 mg of enzyme with CaCO3 (1 g) during 30 min. The immobilized lipase was more stable toward organic solvents than the free enzyme. It retained about 90% of its original activity in the presence of ethanol and methanol. After that, the immobilized enzyme was used for biodiesel production by transesterification process between waste oil and methanol or ethanol during 24 h at 30 °C. Our results show that the lipase can be utilized efficiently in biodiesel industry. Likewise, we have demonstrated that the immobilized enzyme may be implicated in the biodegradability of waste grease; the maximum conversion yield into fatty acids obtained after 12 h at 30 °C, was 57%.

Lipase-catalyzed selective esterification of catechin

Catechins show strong antioxidant, antitumoral, antiviral, and anti-inflammatory activities. The uses of catechins in food, cosmetic, and pharmaceutical formulations seem very attractive. Unfortunately, solubility and stability of catechins are poor in apolar media, which limits their efficient uses. In order to improve the solubility of catechins in the oil phase and maintain their oxidation resistance, a regioselective enzymatic acylation was investigated. The effects of reaction medium, water content, carbon chain length of acyl donor and other factors on the acylation reaction were studied, catechins were enzymatically esterified with an aliphatic acid (stearic acid) using an immobilized lipase Novozym 435 in n-butanol. The results show that when the ratio between catechins and stearic acid was 1:5, adding molecular sieves 4A after 11 h of reaction and the temperature of 60 °C led to the maximum conversion yield of 60.36%. Studies have shown that catechin stearate has a higher antioxidant activity than vitamin E and dibutyl hydroxytoluene (BHT).

Ionic liquid coupled with nickel salt for enhancing the hydro-liquefaction efficiency of the major biomass components

Ionic liquid combined with metal species is considered as a promising catalytic system for biomass liquefaction, which complies with the requirement of green chemistry and promotes utilization of biomass resources. The catalytic systems containing imidazolium-based ionic liquids and nickel chloride were applied to the hydro-liquefaction of major biomass constituents (cellulose, xylan and lignin) in this work. The anion type in ionic liquid played a vital role in the liquefaction of feedstock. The results indicated that the maximum conversion and bio-oil yield were achieved in 1-butyl-3-methylimidazolium bromide ([BMIM]Br)/NiCl2 system, which was attributed to the strong nucleophile and coordinating capacity of bromide ion. The ionic liquid-based catalyst was more effective in the conversion of cellulose and xylan, due to their high reactivity. Additionally, the ionic liquid-based catalyst facilitated the thermal degradation of feedstocks and intermediates, resulting in the increased content of organics with the smaller molecular sizes. The deoxy-hydrogenation reaction was enhanced over ionic liquid-based catalyst, improving the quality of the resulting bio-oils.