Transesterification Efficiency Research Articles

Carbon-based magnetic nano-particle utilizing nano-biochar as core and its immobilizing lipase for biodiesel preparation

Using the transesterification capacity of lipase to produce eco-friendly biodiesel is a promising method for the achievement of a Net Zero future. The method of immobilized lipase enhances the usability of the enzyme and improves its stability. Carbon-based magnetic nano-particles (C-MNPs) with nano-biochar as the precipitation core were prepared as the support to immobilize Candida antarctica lipase B (CalB) for biodiesel preparation. The nano-biochar particles were derived through the calcination of rice straw powder and subsequently ground to the nanoscale. FT-IR, XRD, SEM, and VSM results showed that the obtained C-MNPs with a diameter of 13–17 nm were showing excellent superparamagnetism, and effectively immobilized the lipase on them (CalB@C-MNPs). The optimal reaction conditions in a 100-mL stoppered flask for biodiesel production were dissolving 5 g soybean oil in 3 mL tert-butanol solvent, adding 1.16 mL methanol (molar ratio of methanol to oil 5:1), 0.15 mL water, and 0.2 g CalB@C-MNPs, and then shaking at 200 rpm and 30 °C for 24 h. Its primarily optimized conversion efficiency of biodiesel was 83.1 %. After repeated use of immobilized CalB for 8 cycles, the remaining activity and biodiesel yield were 79.7 % and 66.3 %, respectively. As a robust catalyst, CalB@C-MNPs exhibited outstanding transesterification efficiency, the ability for rapid recovery under an external magnetic field, and a promising candidate in biodiesel production.

Optimization of Enzymatic Transesterification of Acid Oil for Biodiesel Production Using a Low-Cost Lipase: The Effect of Transesterification Conditions and the Synergy of Lipases with Different Regioselectivity.

This study describes the enzymatic production of second-generation biodiesel using low-quality acid oil as a substrate. Biolipasa-R, a commercially available and low-cost lipase, was employed for enzymatic transesterification. Response surface methodology was applied to optimize the enzymatic transesterification process. The optimal conditions for biodiesel production, which comprised 42% lipase concentration (per weight of oil), 32% water content (per weight of oil), a methanol to oil molar ratio of 3:1, pH 7.0 and reaction temperature 30°C, resulted in the highest fatty acid methyl ester (FAME) content (71.3%). Subsequently, the synergistic effect of two lipases with different regioselectivities under the optimum transesterification conditions was studied, aiming at the enhancement of process efficiency. The transesterification efficiency of immobilized Biolipasa-R was determined and compared to that of Biolipasa-R in its free form. The results revealed a good performance on FAME content (66.5%), while the recycling of immobilized lipase resulted in a decrease in transesterification efficiency after three consecutive uses.

A Study of Green Synthesis of Nano-TiO2 Catalyst by Gossypium Leaf Extract and Its Nanocatalysis in the Synthesis of Biofuel from Gossypium Seed Oil

Synthesis of TiO2 nanoparticles by aqueous leaf extract of Gossypium (Gossypiumarboretum) leaves on meta titanic acid [TiO(OH)2]. Rutile tetragonal TiO2 nanoparticles were characterized by XRD, SEM and TEM studies and their particle size was calculated, which was below 100 nm. The Obtained TiO2NPs were used as catalysts in the transesterification of Gossypium seed oil, which enhanced the rate of reaction. Thus, it is a very attractive catalyst for biodiesel production from Gossypium seed oil. The effect of the amount of nano-TiO2 catalyst and microwave heating was studied. In this study, the preparation of both catalyst and biodiesel from the parts of the same Gossypium plant and the feasibility of carrying out the microwave-assisted transesterification (green process) of Gossypium seed oil by using biogenic nanoTiO2 catalyst was explored. They improve the efficiency of transesterification. The used catalyst can be recycled by simple filtration and reused without reduction in its activity. It is a green method (affords nontoxic and noncorrosive medium), clean reaction, simple experimental, isolation procedures, gives high yield and the properties of synthesized biodiesel are in good agreement with that of diesel oil. So, it may be used alone or by blending with diesel.

Designing hydrolysis-resistant Ti/Zn bimetallic catalyst based on the coordination activation mechanism to synthesize high molecular weight poly (1,5-pentene terephthalate) (PPeT)

The high molecular weight poly (1,5-pentene terephthalate) synthesis and its molecular weight distribution control are still challenging, and one of the critical problems is the lack of efficient catalysts. Based on the coordination activation mechanism, a heavy metal free, hydrolysis-resistant and 1,5-Pentanediol soluble Ti/Zn bimetallic catalyst has been synthesized and characterized. The Ti/Zn bimetallic active center increases electron-absorption effect in catalyst to promote the esterification process, and the diol-metal alkoxide structure increases the production of oligomer ligands, which can effectively improve transesterification efficiency. The optimal polycondensation reaction temperature for PPeT synthesized with Ti/Zn bimetallic catalyst can be reduced to 230 °C, with an average reaction rate of 90.33 g mol−1·min−1. The number average molecular weight of PPeT can be increased to 3.02 × 104 g mol−1, and the polymer dispersive index can be as low as 1.90. As the number average molecular weight increases, poly (1,5-pentene terephthalate) has a tensile strength of 29.80 MPa and an elongation at break of 16.39%. More importantly, Ti/Zn bimetallic catalyst retains excellent catalytic activity after treatment with boiling water and has significantly improved hydrolysis resistance and storage stability. Ti/Zn bimetallic catalyst can significantly increase the molecular weight and melt viscosity of poly (1,5-pentene terephthalate), giving it the potential for a wider range of applications in plastics and fiber fields.

Comparative study of biofuel production based on spent coffee grounds transesterification and pyrolysis: Process simulation, techno-economic, and life cycle assessment

Biomass is an interesting energy source to replace fossil fuels for carbon neutrality, which is called biofuel. Spent coffee grounds (SCG) have the potential for the biofuel production since it is generated a lot due to the increased coffee consumption, and it has a high heating value. In this study, to evaluate the economic and environmental feasibilities of biofuel from SCG, the feasibilities of biofuel production by transesterification and pyrolysis of SCG were estimated and compared via process simulation, techno-economic analysis, and life cycle assessment. Consequently, the production cost and CO2 emissions of transesterification were 3.08 times and 6.92 times larger than pyrolysis because feedstock pretreatment was necessary before the transesterification and pretreatment efficiency were low. Pyrolysis biofuel had a low 32.18 MJ kg−1 higher heating value compared to the 40.10 MJ kg−1 of transesterification biofuel due to the water contents depending on the cooling temperature of products. By varying efficiency and cooling temperature through the sensitivity analysis, costs became 30.76–43.71 $ GJ−1 and 8.82–12.35 $ GJ−1 for transesterification and pyrolysis, respectively. Although efficiency improved, transesterification cost could not overcome pyrolysis because of the additional pretreatment and separation. The CO2 emissions were reduced greatly in the transesterification system while the pyrolysis system gradually increased. Even though the pyrolysis system could emit more CO2 when transesterification efficiency improved, pyrolysis recycling would be proper for the SCG feedstock because of the economic feasibility.

Diversification of product-derived ionic liquids and application in DMC synthesis without introducing any impurities

Various strongly basic ionic liquids with distinctive structures, including single and double ended quaternary ammonium and phosphorus salts, were first synthesized based on hydroxyethoxy anion (HOCH2CH2O–) from the product ethylene glycol. Nature was characterized by NMR, FTIR, TG and acid-base titration. Its alkali strength was equivalent to that of sodium methoxide, demonstrating superior alkalinity. Influences of cation structures and C1-C4 alcohols structures on transesterification efficiency were investigated. Under mild conditions (68 °C for 5 min), DMC yield was 42.8% with a TOF value of 2853.6 h−1 when [TBAB]OCH2CH2OH as catalyst with only 0.18% EC molar content, indicating good catalytic performance. Comparison was made for reaction results between the synthesized catalysts and reported catalysts in literatures. The reaction mechanism was further deduced. Activation energies of positive and reverse reactions were determined as Ea+=32.0 kJ·mol−1 and Ea-=15.3 kJ·mol−1 through kinetics calculation. Relying on its decomposability and recyclability of decomposition products, a new catalyst circulation process without introducing any impurities was proposed and verified.

Flexible Vitrimers for Self‐healable Triboelectric Nanogenerators

AbstractDespite rapid advancements in the development of triboelectric nanogenerators (TENG), mechanical defects generated during their working condition limit the service lifetime of these devices. Polyester‐based vitrimers can offer a solution to solve this issue via their dynamic bond exchange reactions. However, they often require high temperatures and a long time to crosslink, rendering them not useful for large‐scale TENG fabrication. To solve these issues, a self‐healable vitrimer‐based triboelectric nanogenerator (VITENG) is developed based on diacrylate poly(dimethylsiloxane) (AA‐PDMS) via a fast thiol‐Michael reaction. By including 2,3‐dihydroxypropyl methacrylate (DHPMA), hydroxy end dangling side chains are generated in the matrix, which increase the PDMS network's flexibility and transesterification efficiency. Efficient transesterification occurs on the abundant dynamic β‐hydroxy ester bonds in the PDMS network, resulting in 100% efficient mechanical damage repair. The VITENG demonstrates a good performance with an output voltage of 135 V under a load of 10 N, demonstrating the potential for mechanical energy harvesters with long lifetimes and high design flexibility.

Development of transesterification model for safe technology of chemical modification of oxidized fats

The object of research is the process of chemical transesterification of palm olein with increased oxidation indicators in the presence of potassium glyceroxide catalyst. Transesterification is an important method of fat modification. The use of fats with increased oxidation indicators leads to the deactivation of common catalysts and a decrease in the efficiency of the process. There is a need to increase the dosage of catalysts, increase the process temperature, which negatively affects the product quality. An alternative transesterification catalyst (potassium glyceroxide) was used for the transesterification of palm olein with increased oxidation indicators. Palm olein (CAS Number 93334-39-5) with standard indicators was used: melting point 22.4 °C, peroxide value 0.8 ½ O mmol/kg, anisidine value 0.3 c. u. Olein was subjected to heating at a temperature of 90 °C in order to increase oxidation indicators, after which it underwent transesterification. The difference in melting points of the initial and transesterified palm olein was used as a parameter of process efficiency. The maximum limit values of the oxidation indicators at which the process is effective are: peroxide value 12.7 ½ O mmol/kg, anisidine value 10.4 c. u. The difference in melting points is 12.1 °C, which indicates the efficiency of the process. The qualitative indicators of the obtained transesterified fat indicate compliance with DSTU 4336 (CAS Number 97593-46-9): melting point 34.5 °C, peroxide value 1.2 ½ O mmol/kg, anisidine value 1.0 c. u. The results of the research make it possible to use fat with increased oxidation indicators without pretreatment and predict the efficiency of transesterification depending on the fat indicators. This will increase profitability and reduce production waste.

Direct transesterification of microalgae after pulsed electric field treatment

AbstractBACKGROUNDLipid extraction is a major bottleneck for the commercialization of microalgae due to energy costs involved during solvent recycling. Direct transesterification offers the possibility to bypass the extraction step by immediately converting the lipids to fatty acid methyl esters (FAMEs). In this study, the efficiency of direct transesterification after pulsed electric field (PEF) treatment was evaluated. Freshly harvested Auxenochlorella protothecoides (A. protothecoides), cultivated either autotrophically or mixotrophically, was subjected to PEF. Two treatment energies were tested, 0.25 and 1.5 MJ kgdw−1, and results were compared with those for conventional two‐step transesterification.RESULTSFor autotrophically grown A. protothecoides, the percentage of the total FAMEs recovered from untreated biomass and microalgae treated with 0.25 MJ kgdw−1 was 30% for both cases, while for 1.5 MJ kgdw−1 it was 65%. A 24 h incubation step between PEF treatment and direct transesterification significantly improved the results. Untreated biomass remained stable with 30% of FAMEs, while with both treatment energies a 97% FAME recovery was achieved. However, for mixotrophic A. protothecoides the process was not as effective. Approximately 30% of FAMEs were recovered for all three conditions immediately after PEF with only a marginal increase after incubation. The reason for this different behavior of the two cultivation modes is unknown and under investigation.CONCLUSIONSOverall, the synergy between PEF and direct transesterification was proven to have potential, in particular for autotrophic microalgae. Its implementation and further optimization in a biorefinery therefore merit further attention. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Influence of the glycerin content in the preparation of calcium diglyceroxide from eggshell applied in the residual oil transesterification

AbstractCurrently, biodiesel is pointed out worldwide as the main alternative in the complementation and substitution of petrochemical diesel. However, the current industrial route of synthesis of this biofuel depends on the cost of raw materials (which are also destined for food purposes) and the expense of the production process. Aiming to remedy this obstacle, the use of solid, sustainable, low‐cost, efficient, and reusable catalysts in residual raw materials, such as waste cooking oils, has been highlighted as a promising alternative. This work focused on studying the influence of the glycerin content used in the preparation by wet impregnation of catalyst calcium diglyceroxide in the efficiency of transesterification of waste cooking oil. The catalyst was synthesized from CaO from chicken eggshell, raw glycerin co‐product from biodiesel, and methanol. The transesterification reactions were performed using 120 g of frying residual oil, methanol: oil molar rate of 6:1, constant shaking, and reaction temperature of 63 ± 1°C for 180 min. The catalyst material synthesized with residual glycerin was active for four reactions (without reactivation of its sites) with high percentages of efficiency of 96.13, 96.85, 95.93, and 91.65, respectively. It was noted that the glycerol purity correlated with changes in the structural morphology of the final compound, as well as changes in the leaching rate, acidity index, water content, and ester content of the blends. It was found that adding 15% water to the lipid material correlated with an increase in ester content (99%) in the synthesized biodiesel.

Simultaneous Extraction of Rapeseed Oil and Enzymatic Transesterification with Butanol in the Mineral Diesel Medium

Increasing environmental pollution is driving an increase in the production and use of biofuels. The cost price of biodiesel could be reduced by using low-quality oilseeds unfit for human consumption and by applying the simultaneous oil extraction and transesterification process, avoiding the oil pressure stage. The purpose of this study was to investigate the enzymatic biofuel production process (in situ) by using rapeseed with high oil acidity for simultaneous oil extraction and transesterification with a mixture of butanol and mineral diesel fuel. The investigation of the in situ process was performed using a mixture of butanol and mineral diesel and the most effective biocatalyst Lipozyme TL IM was selected. The novelty of this paper consists of the fact that mineral diesel was used as the oil extractant, and the amount chosen was such that, at the end, a mixture of fuel with a ratio 9:1 of mineral diesel to biodiesel was be produced. The experiments were carried out using ground rapeseeds under laboratory conditions. The efficiency of oil extraction was investigated by the FTIR spectrometry method, and the efficiency of transesterification was determined by the gas chromatography method. It was found that the optimal reaction duration was 7 h, reaction temperature was 40 °C, and lipase content was 6% (from the oil content in rapeseed). An oil extraction efficiency of 99.92 ± 0.04 (w/w) was observed at these conditions. A transesterification degree of 99.08 ± 0.08% (w/w) met with the requirements of the standards for biodiesel fuel. The physical and chemical properties of the produced fuel mixture met the requirements of the standards for mineral diesel and biodiesel; therefore, it can be used in diesel engines.

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

Application of Microalgae Biomass for Biodiesel Fuel Production

Recently, there has been a growing interest in the use of new types of cheaper raw materials for biodiesel production. There are many prospects for microalgae, which do not compete for land with conventional biodiesel raw materials, are characterized by rapid reproduction and high biomass accumulation, and under certain conditions, some are able to accumulate a large amount of oil. A number of studies have been conducted on the extraction of oil from microalgae cells and transesterification with various acyl receptors. This paper provides an overview of the results of research on microalgal biomass preparation and oil extraction. Indicators of the quality of the oil are presented and its suitability for biodiesel synthesis is analyzed. The homogeneous and heterogeneous catalysts used for oil transesterification are described and the optimal conditions of the process when using various alcohols as acyl receptors are presented. Much attention is paid to the parameters affecting the transesterification efficiency and biodiesel yield. The physical and chemical, and operational and environmental properties of biodiesel obtained from algae oil are analyzed. The evaluation of the economic efficiency of biodiesel synthesis is also presented.

Optimization and Comparison of Biodiesel Production Process by Electric Heating and Microwave-Assisted Heating Transesterification for Waste Cooking Oil via One-Way Experiments and ANOVA

Base-catalyzed transesterification of waste cooking oils (WCOs) into biodiesel is a widely used renewable fuel production technology. The traditional heating method for this process is electric heating (EH), while microwave-assisted heating (MW) has also received extensive attention in recent years. This study compares the two reaction processes in detail by one-way experiments and ANOVA. Catalyst content, reaction temperature (average temperature), and alcohol–oil molar ratio are key factors for these two transesterification processes. The maximum FAME yield of both EH and MW processes appeared at 1.0% catalyst concentration, with the reaction temperature around 60°C, while the MW process called for more methanol. It is speculated that the acid value of WCOs may be closely related to the time required for transesterification as well. The MW process can improve the transesterification efficiency, which is shown in kinetics as much larger than the reaction constant of the EH process and about one-tenth of the activation energy.

Optimization of Biodiesel Production Parameters from Cucurbita maxima Waste Oil Using Microwave Assisted via Box-Behnken Design Approach

The production of biodiesel from vegetables or fruits waste oils has high potential as renewable energy. The Cucurbita maxima wastes are massive source of oils, which are believed to indicate the possible sources of renewable energy whose biodiesel can be produced. Hence, the study explores the potential of the Cucurbita maxima wastes, for the production of biodiesel. In this study, the Soxhlet extraction method was used to extract Cucurbita maxima waste oil using an organic solvent. Through Box-Behnken design (BBD), the effects of methanol to oil molar ratio (6–10), catalyst concentration (2–6%), and reaction time (45–75 min) on the transesterification efficiency of methyl esters were investigated. The oil contents of Cucurbita maxima waste was found to be 44.6 ± 0.21 %. This oil was characterized, and after obtaining the pure characterized oil, biodiesel was produced using microwave assisted by the transesterification process. The optimum conversion efficiency of the Cucurbita maxima waste oil to fatty acid methyl ether was 97.76%, at the optimal parameters, methanol to oil ratio (8.4 : 1), catalyst concentration (3.14%), and reaction time (57.12 min). The results revealed that all parameters have a significant effect on the yield of biodiesel ( p < 0.0001 ). The physicochemical properties reveal that the Cucurbita maxima waste oil could be applied as a potential source of material for methyl ester production. The fatty acid profile of the oil indicated that it was mainly composed of unsaturated fatty acid, which ensures good flow properties of the fuel. The results of these studies showed the prospective of Cucurbita maxima wastes as a new potential feedstock for biodiesel production.

How to improve the efficiency of biocatalysis in non-aqueous pure deep eutectic solvents: A case study on the lipase-catalyzed transesterification reaction

Non-aqueous biocatalysis has been expanding the application fields of biocatalysis and is playing an increasingly important role in industrial biocatalysis. Deep eutectic solvents (DESs) have been recognized as green reaction media of non-aqueous biocatalysis. To provide guidance for improving the catalytic performance of enzymes in pure DESs, Candida antarctica lipase B (CALB) catalyzed transesterification reaction was chosen as the model reaction to assess the catalytic efficiency in different series of pure DESs. The catalytic efficiency of CALB was strongly influenced by the properties of DESs. Hydrophobic DESs caused less inactivation of CALB than hydrophilic DESs. The highest yield in hydrophobic DESs reached 56.75% after 12 h. The amount of carboxyl group in hydrophobic DESs, the amount of hydroxyl group in hydrophilic DESs, and the length of carbon chain had positive impacts on the catalytic efficiency of CALB in DESs. Learning from the CALB behaviors in DESs, a preliminary attempt in rational design DESs for higher transesterification efficiency was provided. Except for reaction media, the catalytic activity of CALB in DESs was improved by medium engineering means and enzyme engineering measures, such as adding a trace amount of water, imprinting CALB with pH buffer or inorganic salt, and protecting CALB by lyoprotectants. Synergistic effect of multiple activation methods could also be observed in improving the catalytic efficiency. This study can provide insights into expanding the application of DESs in non-aqueous biocatalysis.

Optimized biodiesel production from C. innophyllum bio-oil using Kriging and Ann predicitive models

This work aimed at optimizing the two-stage transesterification efficiency of the production of C. inophyllum biodiesel using artificial neural network and Kriging predictive models. Response surface methodology was used to develop the central rotatable composite design of 27 trial experimental runs with variations in the input process parameters like methanol to oil molar ratio, potassium hydroxide catalyst loading, and reaction time. A multi-layered non-linear regressive artificial neural network model with feed-forward propagation and a numerical surrogate Kriging model was used to predict the C. inophyllum biodiesel yield. The efficacy of the developed model was verified using analysis of variance by com-paring its coefficient of determination and the mean relative percentage deviation values. The optimized C. inophyllum biodiesel as 98.1% is derived with 0.94 v/v of methanol to oil molar ratio, 0.98 wt.% of potassium hydroxide catalyst loading, and 80 minutes reaction time with 70?C constant reaction temperature as predicted by Kriging model. The optimized parameters were also verified experimentally.

Kinetic and Transesterification Properties of Lipase from Sprouted Melon (Cucumeropsis manni) Seeds


 
 
 
 
 Crude lipase (acetone powder) was extracted from freshly sprouted melon seeds (Cucumeropsis manni). The activity, kinetic properties (effect of time, pH, and enzyme and substrate concentration, respectively) as well as the ability of the crude lipase to catalyze the production of methyl esters (biodiesel) were examined. The enzyme activity was determined using n-hexane as the solvent (1:2 v/w solvent: substrate ratio) and the transesterification product was analyzed by HPLC. A linear relationship was observed between reaction time and rate of lipolysis with the optimal activity at 2hr of incubation. Furthermore, the lipase was optimally active at acid pH 5 and lipolysis was achieved optimally when the amount of enzyme was 2.0g. Rate of lipolysis was observed to increase linearly at concentrations up to 5.0g of substrate above which a drop in the rate, with no apparent decrease in activity, was observed. The Km (6.25g) and Vmax (13.33%FFA/hr) were also determined. Analysis of the transesterification product yielded 0.61% alkyl ester, 0.81 %FFA, 93.17% TAG, 4.15% 1, 3-DAG and 1.26% 1, 2-DAG while transesterification efficiency was determined to be at 0.588%. Biodiesel (alkyl esters) prepared with the crude lipase was had a density of 0.872 g/mL while its cloud and pour points were 22°C and 12°C, respectively. The results from this research showed that an active lipase was isolated from sprouted melon seeds. However, the fuel properties of the biodiesel produced did not meet international transportation fuel standards. In order to be used industrially, better reaction conditions need to be established for the lipase.
 
 
 
 

Recent Advances in Feedstock and Lipase Research and Development towards Commercialization of Enzymatic Biodiesel

Biodiesel is a biodegradable, renewable, and carbon-neutral alternative to petroleum diesel that can contribute to the global effort of minimizing the use of fossil fuels and meeting the ever-growing energy demands and stringent environmental constraints. The aim of this work was to (1) review the recent progress in feedstock development, including first, second, third, and fourth-generation feedstocks for biodiesel production; (2) discuss recent progress in lipase research and development as one of the key factors for establishing a cost-competitive biodiesel process in terms of enzyme sources, properties, immobilization, and transesterification efficiency; and (3) provide an update of the current challenges and opportunities for biodiesel commercialization from techno-economic and social perspectives. Related biodiesel producers, markets, challenges, and opportunities for biodiesel commercialization, including environmental considerations, are critically discussed.

Diacerein as a Promising Acyl Donor in Biosynthetic Acetyl-CoA and Glycosyl Esters Mediated by a Multifunctional Maltose O-Acetyltransferase from Escherichia coli.

Acetyl-coenzyme A (acetyl-CoA) is an important donor for acetylation modifications of nutritional supplements. The existing enzymatic methods for acetyl-CoA synthesis suffer from cofactor dependence, donor inaccessibility, and biocatalyst instability, leading to its high cost. Hence, a promising alternative is highly desired. Herein, a maltose O-acetyltransferase (MAT) with cofactor independence had been identified as a stable acetyl-CoA-synthesizing biocatalyst in a screen of the Escherichia coli genome. Under the action of MAT, an anthraquinone medicine containing two acetyl groups, diacerein, was screened as an acetyl donor. Saturation mutagenesis at Glu125 was performed to increase the acetyl-CoA-synthesizing capacity of MAT, while decreasing the accompanying hydrolase activities. A mutant MAT-E125F was thus generated and could convert diacerein and CoA into the highest yield of 3892.70 mg/L acetyl-CoA. Moreover, MAT could synthesize puerarin 6″-O-acetate and other glycosyl esters through acetyl-CoA-dependent acetylation or diacerein-based transesterification reaction. To most of the tested glycosides, the transesterification efficiency was higher than that of acetylation. The mutant MAT-E125V acquired the highest conversion of 94.0% to puerarin 6″-O-acetate through transesterification, while MAT-E125N yielded the highest conversion of 68.5% through acetylation. Taking together, the multifunctional MAT displayed a potent acetyl-CoA- and glycosyl ester-synthesizing capacity using diacerein as an acetyl donor.