Enzymatic transesterification of Jatropha oil

Enhanced Enzymatic Performance of Immobilized Pseudomonas fluorescens Lipase on ZIF-8@ZIF-67 and Its Application to the Synthesis of Neryl Acetate with Transesterification Reaction

In this study, hybrid skeleton material ZIF-8@ZIF-67 was synthesized by the epitaxial growth method and then was utilized as a carrier for encapsulating Pseudomonas fluorescens lipase (PFL) through the co-precipitation method, resulting in the preparation of immobilized lipase (PFL@ZIF-8@ZIF-67). Subsequently, it was further treated with glutaraldehyde to improve protein immobilization yield. Under optimal immobilization conditions, the specific hydrolytic activity of PFL@ZIF-8@ZIF-67 was 20.4 times higher than that of the free PFL. The prepared biocatalyst was characterized and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR). Additionally, the thermal stability of PFL@ZIF-8@ZIF-67 at 50 °C was significantly improved compared to the free PFL. After 7 weeks at room temperature, PFL@ZIF-8@ZIF-67 retained 78% of the transesterification activity, while the free enzyme was only 29%. Finally, PFL@ZIF-8@ZIF-67 was applied to the neryl acetate preparation in a solvent-free system, and the yield of neryl acetate reached 99% after 3 h of reaction. After 10 repetitions, the yields of neryl acetate catalyzed by PFL@ZIF-8@ZIF-67 and the free PFL were 80% and 43%, respectively.

Lipase-Catalyzed Preparation and Optimization of Structured Phosphatidylcholine Containing Nervonic Acid

This study investigated the incorporation of nervonic acid into the chemical structure of phosphatidylcholine via a lipase-catalyzed acidolysis reaction to obtain a functional phospholipid. Lipase immobilization was conducted, and Amberlite XAD7-HP was selected as a carrier to immobilize phospholipase A1 (PLA1) for subsequent experiments. The main acidolysis reaction parameters, including enzyme load, substrate ratio, temperature, and water content, were studied against the reaction time. The optimum reaction conditions obtained were enzyme load, 20%; reaction temperature, 55 °C; water content, 1%; and reaction time, 9 h. The maximum incorporation of nervonic acid into phosphatidylcholine was 48 mol%, with PC recovery at 61.6 mol%. The positional distribution of structured phosphatidylcholine shows that nervonic acid was found in the sn-1 position due to enzyme specificity and in the sn-2 position, possibly due to acyl migration.

Combined immobilized lipases for effective biodiesel production from spent coffee grounds

This work describes the enzymatic transesterification of the oil extracted from SCGs for synthesis of biodiesel as a promising alternative to diesel fuels based on petroleum. Biocatalysts from various sources were tested for biodiesel synthesis using coffee oil among which CaCO3- immobilized Staphylococcus aureus and Bacillus stearothermophilus showed the highest conversion yields (61 ± 2.64% and 64.3 ± 1.53%, respectively) in 4 h. In further optimizing reaction parameters, methanol to oil molar ratio, biocatalyst quantity, water content, as well as incubation time and temperature markedly improved oil-to-biodiesel conversion up to 99.33 ± 0.57 % in a solvent free reaction after 12 h at 55 °C. A mixture of inexpensive CaCO3-immobilized bacterial lipases at a 1:1 ratio was the best environment-friendly catalyst for biofuel synthesis as well as the ideal trade-off between conversion and cost. Obtained coffee biodiesel remained stable beyond 40 days at ambient storage conditions and its chemical characteristics were comparable to those of other known biodiesels according to the European requirements (EN14214). Collectively, SCGs, after oil extraction, could be an ideal substrate for the production of an environment-friendly biodiesel by using appropriate mixture of CaCO3-immobilized lipases.

A comprehensive review on nanocatalysts and nanobiocatalysts for biodiesel production in Indonesia, Malaysia, Brazil and USA

Biodiesel is an alternative to fossil-derived diesel with similar properties and several environmental benefits. Biodiesel production using conventional catalysts such as homogeneous, heterogeneous, or enzymatic catalysts faces a problem regarding catalysts deactivation after repeated reaction cycles. Heterogeneous nanocatalysts and nanobiocatalysts (enzymes) have shown better advantages due to higher activity, recyclability, larger surface area, and improved active sites. Despite a large number of studies on this subject, there are still challenges regarding its stability, recyclability, and scale-up processes for biodiesel production. Therefore, the purpose of this study is to review current modifications and role of nanocatalysts and nanobiocatalysts and also to observe effect of various parameters on biodiesel production. Nanocatalysts and nanobiocatalysts demonstrate long-term stability due to strong Brønsted-Lewis acidity, larger active spots and better accessibility leading to enhancethe biodiesel production. Incorporation of metal supporting positively contributes to shorten the reaction time and enhance the longer reusability. Furthermore, proper operating parameters play a vital role to optimize the biodiesel productivity in the commercial scale process due to higher conversion, yield and selectivity with the lower process cost. This article also analyses the relationship between different types of feedstocks towards the quality and quantity of biodiesel production. Crude palm oil is convinced as the most prospective and promising feedstock due to massive production, low cost, and easily available. It also evaluates key factors and technologies for biodiesel production in Indonesia, Malaysia, Brazil, and the USA as the biggest biodiesel production supply.

Biofuels from Renewable Sources, a Potential Option for Biodiesel Production

Ever-increasing population growth that demands more energy produces tremendous pressure on natural energy reserves such as coal and petroleum, causing their depletion. Climate prediction models predict that drought events will be more intense during the 21st century affecting agricultural productivity. The renewable energy needs in the global energy supply must stabilize surface temperature rise to 1.5 °C compared to pre-industrial values. To address the global climate issue and higher energy demand without depleting fossil reserves, growing bioenergy feedstock as the potential resource for biodiesel production could be a viable alternative. The interest in growing biofuels for biodiesel production has increased due to its potential benefits over fossil fuels and the flexibility of feedstocks. Therefore, this review article focuses on different biofuels and biomass resources for biodiesel production, their properties, procedure, factors affecting biodiesel production, different catalysts used, and greenhouse gas emissions from biodiesel production.

Biodiesel Production by Single and Mixed Immobilized Lipases Using Waste Cooking Oil

Biodiesel is one of the important biofuels as an alternative to petroleum-based diesel fuels. In the current study, enzymatic transesterification reaction was carried out for the production of biodiesel from waste cooking oil (WCO) and experimental conditions were optimized, in order to reach maximum biodiesel yield. Bacillus stearothermophilus and Staphylococcus aureus lipase enzymes were individually immobilized on CaCO₃ to be used as environmentally friendly catalysts for biodiesel production. The immobilized lipases exhibited better stability than free ones and were almost fully active after 60 days of storage at 4 °C. A significant biodiesel yield of 97.66 ± 0.57% was achieved without any pre-treatment and at 1:6 oil/methanol molar ratio, 1% of the enzyme mixture (a 1:1 ratio mixture of both lipase), 1% water content, after 24 h at 55 °C reaction temperature. The biocatalysts retained 93% of their initial activities after six cycles. The fuel and chemical properties such as the cloud point, viscosity at 40 °C and density at 15 °C of the produced biodiesel complied with international specifications (EN 14214) and, therefore, were comparable to those of other diesels/biodiesels. Interestingly, the resulting biodiesel revealed a linolenic methyl ester content of 0.55 ± 0.02% and an ester content of 97.7 ± 0.21% which is in good agreement with EN14214 requirements. Overall, using mixed CaCO₃-immobilized lipases to obtain an environmentally friendly biodiesel from WCO is a promising and effective alternative for biodiesel production catalysis.

Biodiesel Production from Brassica juncea Using Oleaginous Yeast

The present study explores the potential of Brassica juncea as a low-cost substrate for biodiesel production through the growth of oleaginous yeast. Firstly, the selected lignocellulosic biomass, i.e., Brassica juncea, was thermochemically pretreated using dilute sodium hydroxide. Optimization of thermochemical pretreatment resulted in significant removal of lignin and hemicellulose with 8.4% increase in cellulose content. Further, the sugar hydrolysate of pretreated biomass was used as a substrate for the growth of selected oleaginous yeast (Cryptococcus sp. MTCC 5455). Lipid and biomass production was optimized using central composite design (CCD) based on response surface methodology (RSM). Maximum biomass and lipid content of 32.50 g/L and 11.05 g/L, respectively, was obtained at 30 °C temperature, pH 6.0, and after 5 days of incubation. The oleaginous yeast lipid was further transesterified using immobilized lipase. The highest fatty acid methyl ester 15% FAME yield was obtained after 10 h of enzymatic reaction. Next, the results of specific gravity, viscosity, flash points, and cloud point of obtained biodiesels were conformed to the ASTM D975 standard. Overall, the present study put forth the cost-effective approach for lignocellulosic biomass-based oleaginous lipid production toward the green synthesis of biodiesel.

Valorisation of xylose to renewable fuels and chemicals, an essential step in augmenting the commercial viability of lignocellulosic biorefineries

Biologists and engineers are making tremendous efforts in contributing to a sustainable and green society. To that end, there is growing interest in waste management and valorisation. Lignocellulosic biomass (LCB) is the most abundant material on the earth and an inevitable waste predominantly originating from agricultural residues, forest biomass and municipal solid waste streams. LCB serves as the renewable feedstock for clean and sustainable processes and products with low carbon emission. Cellulose and hemicellulose constitute the polymeric structure of LCB, which on depolymerisation liberates oligomeric or monomeric glucose and xylose, respectively. The preferential utilization of glucose and/or absence of the xylose metabolic pathway in microbial systems cause xylose valorization to be alienated and abandoned, a major bottleneck in the commercial viability of LCB-based biorefineries. Xylose is the second most abundant sugar in LCB, but a non-conventional industrial substrate unlike glucose. The current review seeks to summarize the recent developments in the biological conversion of xylose into a myriad of sustainable products and associated challenges. The review discusses the microbiology, genetics, and biochemistry of xylose metabolism with hurdles requiring debottlenecking for efficient xylose assimilation. It further describes the product formation by microbial cell factories which can assimilate xylose naturally and rewiring of metabolic networks to ameliorate xylose-based bioproduction in native as well as non-native strains. The review also includes a case study that provides an argument on a suitable pathway for optimal cell growth and succinic acid (SA) production from xylose through elementary flux mode analysis. Finally, a product portfolio from xylose bioconversion has been evaluated along with significant developments made through enzyme, metabolic and process engineering approaches, to maximize the product titers and yield, eventually empowering LCB-based biorefineries. Towards the end, the review is wrapped up with current challenges, concluding remarks, and prospects with an argument for intense future research into xylose-based biorefineries.

Stabilization and operational selectivity alteration of Lipozyme 435 by its coating with polyethyleneimine: Comparison of the biocatalyst performance in the synthesis of xylose fatty esters

Differently modified Lipozyme 435 (L435) (immobilized lipase B from Candida antarctica) preparations were used as biocatalysts in the esterification reaction to synthesize sugar fatty acid esters (SFAEs) from xylose (acyl acceptor) and lauric/palmitic acids (acyl donors) in methyl ethyl ketone (MEK) solvent. The L435 treatment with polyethyleneimine (PEI) (2; 25; and 750 KDa) prevented the enzyme leakage in the crude sugar ester reaction product. The 2 KDa PEI coating of this enzyme preparation produced the highest enzyme stability in MEK, buffer solutions (pHs 5 and 7), and methanol aqueous phosphate buffer at pH 7. Using an excess of the acyl donor (1:5 xylose: fatty acid molar ratio), high xylose conversions (70-84%) were obtained after 24 h-reaction using both, non-modified and PEI (2 KDa) coated L435, but the PEI treated biocatalyst afforded a higher xylose modification degree. After 5 reuse cycles with the L435 coated with PEI 2 KDa, the xylose conversions only decreased 10%, while with the non-treated biocatalyst they decreased by 37%. The formation of SFAEs was confirmed by mass spectrometry, which showed the presence of xylose mono-, di-, and triesters. They exhibited emulsion capacities close to that of a commercial sucrose monolaurate.

Recent advances in biodiesel production: Challenges and solutions

Mono alkyl fatty acid ester or methyl ethyl esters (biodiesel) are the promising alternative for fossil fuel or petroleum derived diesel with similar properties and could reduce the carbon foot print and the greenhouse gas emissions. Biodiesel can be produced from renewable and sustainable feedstocks like plant derived oils, and it is biodegradable and non-toxic to the ecosystem. The process for the biodiesel production is either through traditional chemical catalysts (Acid or Alkali Transesterification) or enzyme mediated transesterification, but as enzymes are natural catalysts with environmentally friendly working conditions, the process with enzymes are proposed to overcome the drawbacks of chemical synthesis. At present 95% of the biodiesel production is contributed by edible oils worldwide whereas recycled oils and animal fats contribute 10% and 6% respectively. Although every process has its own limitations, the enzyme efficiency, resistance to alcohols, and recovery rate are the crucial factors to be addressed. Without any benefit of doubt, production of biodiesel using renewable feedstocks and enzymes as the catalysts could be recommended for the commercial purpose, but further research on improving the efficiency could be an advantage.

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.

Biodiesel Production From Lignocellulosic Biomass Using Oleaginous Microbes: Prospects for Integrated Biofuel Production

Biodiesel is an eco-friendly, renewable, and potential liquid biofuel mitigating greenhouse gas emissions. Biodiesel has been produced initially from vegetable oils, non-edible oils, and waste oils. However, these feedstocks have several disadvantages such as requirement of land and labor and remain expensive. Similarly, in reference to waste oils, the feedstock content is succinct in supply and unable to meet the demand. Recent studies demonstrated utilization of lignocellulosic substrates for biodiesel production using oleaginous microorganisms. These microbes accumulate higher lipid content under stress conditions, whose lipid composition is similar to vegetable oils. In this paper, feedstocks used for biodiesel production such as vegetable oils, non-edible oils, oleaginous microalgae, fungi, yeast, and bacteria have been illustrated. Thereafter, steps enumerated in biodiesel production from lignocellulosic substrates through pretreatment, saccharification and oleaginous microbe-mediated fermentation, lipid extraction, transesterification, and purification of biodiesel are discussed. Besides, the importance of metabolic engineering in ensuring biofuels and biorefinery and a brief note on integration of liquid biofuels have been included that have significant importance in terms of circular economy aspects.

Lipozyme 435-Mediated Synthesis of Xylose Oleate in Methyl Ethyl Ketone

In this paper, we have performed the Lipozyme 435-catalyzed synthesis of xylose oleate in methyl ethyl ketone (MEK) from xylose and oleic acid. The effects of substrates’ molar ratios, reaction temperature, reaction time on esterification rates, and Lipozyme 435 reuse were studied. Results showed that an excess of oleic acid (xylose: oleic acid molar ratio of 1:5) significantly favored the reaction, yielding 98% of xylose conversion and 31% oleic acid conversion after 24 h-reaction (mainly to xylose mono- and dioleate, as confirmed by mass spectrometry). The highest Lipozyme 435 activities occurred between 55 and 70 °C. The predicted Ping Pong Bi Bi kinetic model fitted very well to the experimental data and there was no evidence of inhibitions in the range assessed. The reaction product was purified and presented an emulsion capacity close to that of a commercial sugar ester detergent. Finally, the repeated use of Lipozyme 435 showed a reduction in the reaction yields (by 48 and 19% in the xylose and oleic acid conversions, respectively), after ten 12 h-cycles.

Structure elucidation and docking analysis of 5M mutant of T1 lipase Geobacillus zalihae

5M mutant lipase was derived through cumulative mutagenesis of amino acid residues (D43E/T118N/E226D/E250L/N304E) of T1 lipase from Geobacillus zalihae. A previous study revealed that cumulative mutations in 5M mutant lipase resulted in decreased thermostability compared to wild-type T1 lipase. Multiple amino acids substitution might cause structural destabilization due to negative cooperation. Hence, the three-dimensional structure of 5M mutant lipase was elucidated to determine the evolution in structural elements caused by amino acids substitution. A suitable crystal for X-ray diffraction was obtained from an optimized formulation containing 0.5 M sodium cacodylate trihydrate, 0.4 M sodium citrate tribasic pH 6.4 and 0.2 M sodium chloride with 2.5 mg/mL protein concentration. The three-dimensional structure of 5M mutant lipase was solved at 2.64 Å with two molecules per asymmetric unit. The detailed analysis of the structure revealed that there was a decrease in the number of molecular interactions, including hydrogen bonds and ion interactions, which are important in maintaining the stability of lipase. This study facilitates understanding of and highlights the importance of hydrogen bonds and ion interactions towards protein stability. Substrate specificity and docking analysis on the open structure of 5M mutant lipase revealed changes in substrate preference. The molecular dynamics simulation of 5M-substrates complexes validated the substrate preference of 5M lipase towards long-chain p-nitrophenyl-esters.

Reviewing research on the synthesis of CALB-catalyzed sugar esters incorporating systematic mapping principles

Rigorous evidence reviews must follow specific guidelines designed to improve transparency, reproducibility, and to minimize biases to which traditional reviews are susceptible. While evidence synthesis methods, such as systematic reviews and maps, have been used in several research fields, the majority of reviews published in the realm of chemical engineering are nonsystematic. In this study, we incorporated principles of systematic mapping to conduct a literature review covering research on the synthesis of sugar fatty acid esters (SFAE) with Candida antarctica lipase B (CALB). Our results showed that the simple monosaccharides were the most cited sugars among studies we conducted. The direct use of renewable raw materials and frequently available resources to produce alternative sugar esters (SE) was scarcely reported in our data set. We found that free fatty acids (FFA) were the most commonly cited acyl donors amongst all publications, with lauric, oleic, and palmitic acids accounting for ∼43% of the occurrences. Tertiary alcohols (ter-butyl alcohol (T-but) and 2-methyl-2-butanol (2M2B)) and ionic liquids were the most used solvents to synthesize SE. The co-occurence analysis of keywords involving solvent terms showed that most of the papers evaluated different solvents as reaction media (mostly in the form of a bisolvent system), also investigating the impact of their choice on sugar ester productivities. Given the potential of reviews informing us of research decisions, this article reveals trends and spaces across CALB-catalyzed SE synthesis research, in addition to introducing a new methodological perspective for developing reviews in the field of chemical engineering.

Real-time assessment and characterization of immobilized lipase onto a natural matrix and qualitative reaction kinetic studies using swept-source optical coherence tomography

The current study presents a method based on Optical Coherence Tomography (OCT) for non-destructive, real-time analysis and portrayal of immobilization efficacy for lipase on a natural matrix namely, eggshell. Subsequently, qualitative biochemical reaction kinetics of immobilized lipase was also studied. Successful immobilization of lipase on eggshell was confirmed by the presence of a clear peak in 'A' scan of OCT image. From immobilization kinetics it is clearly observed that the thickness of the highest peak of the A-scan increases significantly and peak intensity saturated after 90 min of incubation. Hydrolysis of oil using immobilized lipase indicated that the release of free fatty acids increased up to 8 h during reaction and the result was in accordance with the 'B' scan data of the OCT system. Changes in scattering coefficient-based analysis were performed with respect to incubation time to showcase the immobilization process and hydrolysis reaction of lipase. Scanning electron microscope analysis with smoother surface indicated presence of lipase on eggshell matrices, with no further change after oil hydrolysis.

Multilayered Nano-Entrapment of Lipase through Organic-Inorganic Hybrid Formation and the Application in Cost-Effective Biodiesel Production

Significant components of cost-effective medium for Magnusiomyces capitatus A4C extracellular lipase (ECL) production were optimized via a five-level factorial design. A simplistic, economical, and green approach was adopted for biomimetic mineralization to prepare multilayered nano-entrapped ECL, which were then applied as biocatalysts for the production of fatty acid methyl ester (FAME). The optimal ECL (0.8 mg protein/mL) and CuSO₄∙5H₂O (1.2 mM) showed the highest capacity for enzyme loading. The ECL-CuSO₄-hybrid showed an 89.7% conversion of triacylglycerides into FAME via transesterification and a 98.7% conversion of oleic acid into FAME via esterification at 72 h. The ECL-CuSO₄-hybrid gave 65% and 78.7% FAME production after 5 successive reuses via transesterification and esterification reactions, respectively. Therefore, these ECL-inorganic hybrid biocatalysts have high economical potential to be used for the production of biodiesel as the future petrodiesel replacement.

Constraints and advances in high-solids enzymatic hydrolysis of lignocellulosic biomass: a critical review

The industrial production of sugar syrups from lignocellulosic materials requires the conduction of the enzymatic hydrolysis step at high-solids loadings (i.e., with over 15% solids [w/w] in the reaction mixture). Such conditions result in sugar syrups with increased concentrations and in improvements in both capital and operational costs, making the process more economically feasible. However, this approach still poses several technical hindrances that impact the process efficiency, known as the "high-solids effect" (i.e., the decrease in glucan conversion yields as solids load increases). The purpose of this review was to present the findings on the main limitations and advances in high-solids enzymatic hydrolysis in an updated and comprehensive manner. The causes for the rheological limitations at the onset of the high-solids operation as well as those influencing the "high-solids effect" will be discussed. The subject of water constraint, which results in a highly viscous system and impairs mixing, and by extension, mass and heat transfer, will be analyzed under the perspective of the limitations imposed to the action of the cellulolytic enzymes. The "high-solids effect" will be further discussed vis-à-vis enzymes end-product inhibition and the inhibitory effect of compounds formed during the biomass pretreatment as well as the enzymes' unproductive adsorption to lignin. This review also presents the scientific and technological advances being introduced to lessen high-solids hydrolysis hindrances, such as the development of more efficient enzyme formulations, biomass and enzyme feeding strategies, reactor and impeller designs as well as process strategies to alleviate the end-product inhibition. We surveyed the academic literature in the form of scientific papers as well as patents to showcase the efforts on technological development and industrial implementation of the use of lignocellulosic materials as renewable feedstocks. Using a critical approach, we expect that this review will aid in the identification of areas with higher demand for scientific and technological efforts.

Engineered Thermoanaerobacterium aotearoense with nfnAB knockout for improved hydrogen production from lignocellulose hydrolysates

BACKGROUND

As a renewable and clean energy carrier, the production of biohydrogen from low-value feedstock such as lignocellulose has increasingly garnered interest. The NADH-dependent reduced ferredoxin:NADP⁺ oxidoreductase (NfnAB) complex catalyzes electron transfer between reduced ferredoxin and NAD(P)⁺, which is critical for production of NAD(P)H-dependent products such as hydrogen and ethanol. In this study, the effects on end-product formation of deletion of nfnAB from Thermoanaerobacterium aotearoense SCUT27 were investigated.

RESULTS

Compared with the parental strain, the NADH/NAD⁺ ratio in the ∆nfnAB mutant was increased. The concentration of hydrogen and ethanol produced increased by (41.1 ± 2.37)% (p < 0.01) and (13.24 ± 1.12)% (p < 0.01), respectively, while the lactic acid concentration decreased by (11.88 ± 0.96)% (p < 0.01) when the ∆nfnAB mutant used glucose as sole carbon source. No obvious inhibition effect was observed for either SCUT27 or SCUT27/∆nfnAB when six types of lignocellulose hydrolysate pretreated with dilute acid were used for hydrogen production. Notably, the SCUT27/∆nfnAB mutant produced 190.63-209.31 mmol/L hydrogen, with a yield of 1.66-1.77 mol/mol and productivity of 12.71-13.95 mmol/L h from nonsterilized rice straw and corn cob hydrolysates pretreated with dilute acid.

CONCLUSIONS

The T. aotearoense SCUT27/∆nfnAB mutant showed higher hydrogen yield and productivity compared with those of the parental strain. Hence, we demonstrate that deletion of nfnAB from T. aotearoense SCUT27 is an effective approach to improve hydrogen production by redirecting the electron flux, and SCUT27/∆nfnAB is a promising candidate strain for efficient biohydrogen production from lignocellulosic hydrolysates.

Enhanced lipid extraction from oleaginous yeast biomass using ultrasound assisted extraction: A greener and scalable process

Soaring demand for alternative fuels has been gaining wide interest due to depletion of conventional fuel, increasing petroleum prices and greenhouse gas emissions. Biodiesel, an alternative fuel, derived from oleaginous microbes has been promising because of short incubation time and easy to scale up. Oleaginous yeast Trichosporon sp. is capable of utilizing glycerol and agro-residues for enhanced lipid synthesis. Lipid extraction from Trichosporon sp. biomass showed highest lipid content with ultrasonic assisted extraction (43 ± 0.33%, w/w) coupled with process parameters than the conventional Soxhlet (30 ± 0.28%, w/w) and Binary solvent [choloroform:methanol, (2:1, v/v)] methods (36 ± 0.38%, w/w), respectively. The standardized process parameters of ultrasonic assisted extraction coupled with chloroform/methanol solvent system resulted 95-97% of conversion efficiency in 20 min at 30 °C with a frequency of 50 Hz and 2800 W power, respectively. Enzymatic transesterification of yeast biomass lipid obtained 85% of fatty acid methyl esters that are predominant with oleic acid methyl ester followed by palmitic and stearic acid methyl esters, respectively. These results substantiate that the ultrasonic assisted extraction is a potential green extraction technique that had reduced time, energy and solvent consumption without compromising on lipid quality. Deploying this green extraction technique could make the biodiesel production process inexpensive and eco-friendly.

Cochineal Waxy Residues as Source of Policosanol: Chemical Hydrolysis and Enzymatic Transesterification

The aim of this study was to obtain and characterise the long-chain alcohols present in policosanol derived from waste from the production of carminic acid, a natural colouring agent widely used in the food industry. The effectiveness of different methods designed for extraction of policosanol from waxy waste was investigated and its content and composition was determined. Triacontanol was the main component in policosanol produced by chemical processes, and it yields up to 13% by alkaline hydrolysis in water and chloroform extraction. Regarding enzymatic transesterification, policosanol was obtained using lipase Candida antarctica recombinant in Aspergillus niger (CAL-Bn) in a reaction medium with toluene. To improve the reaction, different acyl receptors, propanol, butanol, and isopropanol, were tested and molecular sieves were employed to maintain an anhydrous reaction medium. In this case, the policosanol was made up of other long-chain alcohols, but triacontanol was obtained in yields of up to 19% using isopropanol as an acyl receptor. Triacontanol has a great commercial value due to its effect as a promoter of plant growth, and these results contribute to the use and application of this agroindustrial waste in obtaining value-added products.

Performance of Different Immobilized Lipases in the Syntheses of Short- and Long-Chain Carboxylic Acid Esters by Esterification Reactions in Organic Media

Short-chain alkyl esters and sugar esters are widely used in the food, pharmaceutical and cosmetic industries due to their flavor and emulsifying characteristics, respectively. Both compounds can be synthesized via biocatalysis using lipases. This work aims to compare the performance of commercial lipases covalently attached to dry acrylic beads functionalized with oxirane groups (lipases from Candida antarctica type B-IMMCALB-T2-350, Pseudomonas fluorescens-IMMAPF-T2-150, and Thermomyces lanuginosus-IMMTLL-T2-150) and a home-made biocatalyst (lipase from Pseudomonas fluorescens adsorbed onto silica coated with octyl groups, named PFL-octyl-silica) in the syntheses of short- and long-chain carboxylic acid esters. Esters with flavor properties were synthetized by esterification of acetic and butyl acids with several alcohols (e.g., ethanol, 1-butanol, 1-hexanol, and isoamyl alcohol), and sugar esters were synthetized by esterification of oleic and lauric acids with fructose and lactose. All biocatalysts showed similar performance in the syntheses of short-chain alkyl esters, with conversions ranging from 88.9 to 98.4%. However, in the syntheses of sugar esters the performance of PFL-octyl-silica was almost always lower than the commercial IMMCALB-T2-350, whose conversion was up to 96% in the synthesis of fructose oleate. Both biocatalysts showed high operational stability in organic media, thus having great potential for biotransformations.

Realm of Thermoalkaline Lipases in Bioprocess Commodities

For decades, microbial lipases are notably used as biocatalysts and efficiently catalyze various processes in many important industries. Biocatalysts are less corrosive to industrial equipment and due to their substrate specificity and regioselectivity they produced less harmful waste which promotes environmental sustainability. At present, thermostable and alkaline tolerant lipases have gained enormous interest as biocatalyst due to their stability and robustness under high temperature and alkaline environment operation. Several characteristics of the thermostable and alkaline tolerant lipases are discussed. Their molecular weight and resistance towards a range of temperature, pH, metal, and surfactants are compared. Their industrial applications in biodiesel, biodetergents, biodegreasing, and other types of bioconversions are also described. This review also discusses the advance of fermentation process for thermostable and alkaline tolerant lipases production focusing on the process development in microorganism selection and strain improvement, culture medium optimization via several optimization techniques (i.e., one-factor-at-a-time, surface response methodology, and artificial neural network), and other fermentation parameters (i.e., inoculums size, temperature, pH, agitation rate, dissolved oxygen tension (DOT), and aeration rate). Two common fermentation techniques for thermostable and alkaline tolerant lipases production which are solid-state and submerged fermentation methods are compared and discussed. Recent optimization approaches using evolutionary algorithms (i.e., Genetic Algorithm, Differential Evolution, and Particle Swarm Optimization) are also highlighted in this article.

Contribution of Pentose Catabolism to Molecular Hydrogen Formation by Targeted Disruption of Arabinose Isomerase (araA) in the Hyperthermophilic Bacterium Thermotoga maritima

Thermotoga maritima ferments a broad range of sugars to form acetate, carbon dioxide, traces of lactate, and near theoretic yields of molecular hydrogen (H₂). In this organism, the catabolism of pentose sugars such as arabinose depends on the interaction of the pentose phosphate pathway with the Embden-Myerhoff and Entner-Doudoroff pathways. Although the values for H₂ yield have been determined using pentose-supplemented complex medium and predicted by metabolic pathway reconstruction, the actual effect of pathway elimination on hydrogen production has not been reported due to the lack of a genetic method for the creation of targeted mutations. Here, a spontaneous and genetically stable pyrE deletion mutant was isolated and used as a recipient to refine transformation methods for its repair by homologous recombination. To verify the occurrence of recombination and to assess the frequency of crossover events flanking the deleted region, a synthetic pyrE allele, encoding synonymous nucleotide substitutions, was used. Targeted inactivation of araA (encoding arabinose isomerase) in the pyrE mutant was accomplished using a divergent, codon-optimized Thermosipho africanus pyrE allele fused to the T. maritima groES promoter as a genetic marker. Mutants lacking araA were unable to catabolize arabinose in a defined medium. The araA mutation was then repaired using targeted recombination. Levels of synthesis of H₂ using arabinose-supplemented complex medium by wild-type and araA mutant cell lines were compared. The difference between strains provided a direct measurement of H₂ production that was dependent on arabinose consumption. Development of a targeted recombination system for genetic manipulation of T. maritima provides a new strategy to explore H₂ formation and life at an extremely high temperature in the bacterial domain.

IMPORTANCE

We describe here the development of a genetic system for manipulation of Thermotoga maritima T. maritima is a hyperthermophilic anaerobic bacterium that is well known for its efficient synthesis of molecular hydrogen (H₂) from the fermentation of sugars. Despite considerable efforts to advance compatible genetic methods, chromosome manipulation has remained elusive and hindered use of T. maritima or its close relatives as model hyperthermophiles. Lack of a genetic method also prevented efforts to manipulate specific metabolic pathways to measure their contributions to H₂ yield. To overcome this barrier, a homologous chromosomal recombination method was developed and used to characterize the contribution of arabinose catabolism to H₂ formation. We report here a stable genetic method for a hyperthermophilic bacterium that will advance studies on the basic and synthetic biology of Thermotogales.

Genetic Tracing of Jatropha curcas L. from Its Mesoamerican Origin to the World

Jatropha curcas L. (Jatropha), a shrub species of the family Euphorbiaceae, has been recognized as a promising biofuel plant for reducing greenhouse gas emissions. However, recent attempts at commercial cultivation in Africa and Asia have failed because of low productivity. It is important to elucidate genetic diversity and relationship in worldwide Jatropha genetic resources for breeding of better commercial cultivars. Here, genetic diversity was analyzed by using 246 accessions from Mesoamerica, Africa and Asia, based on 59 simple sequence repeat markers and eight retrotransposon-based insertion polymorphism markers. We found that central Chiapas of Mexico possesses the most diverse genetic resources, and the Chiapas Central Depression could be the center of origin. We identified three genetic groups in Mesoamerica, whose distribution revealed a distinct geographic cline. One of them consists mainly of accessions from central Chiapas. This suggests that it represents the original genetic group. We found two Veracruz accessions in another group, whose ancestors might be shipped from Port of Veracruz to the Old World, to be the source of all African and Asian Jatropha. Our results suggest the human selection that caused low productivity in Africa and Asia, and also breeding strategies to improve African and Asian Jatropha. Cultivars improved in the productivity will contribute to expand mass commercial cultivation of Jatropha in Africa and Asia to increase biofuel production, and finally will support in the battle against the climate change.

Selection of Lipases for the Synthesis of Biodiesel from Jatropha Oil and the Potential of Microwave Irradiation to Enhance the Reaction Rate

The present study deals with the enzymatic synthesis of biodiesel by transesterification of Jatropha oil (Jatropha curcas L.) with ethanol in a solvent-free system. Seven commercial lipase preparations immobilized by covalent attachment on epoxy-polysiloxane-polyvinyl alcohol composite (epoxy-SiO₂-PVA) were tested as biocatalysts. Among them, immobilized lipases from Pseudomonas fluorescens (lipase AK) and Burkholderia cepacia (lipase PS) were the most active biocatalysts in biodiesel synthesis, reaching ethyl ester yields (FAEE) of 91.1 and 98.3% at 72 h of reaction, respectively. The latter biocatalyst exhibited similar performance compared to Novozym® 435. Purified biodiesel was characterized by different techniques. Transesterification reaction carried out under microwave irradiation exhibited higher yield and productivity than conventional heating. The operational stability of immobilized lipase PS was determined in repeated batch runs under conventional and microwave heating systems, revealing half-life times of 430.4 h and 23.5 h, respectively.

Biodiesel production from crude jatropha oil catalyzed by immobilized lipase/acyltransferase from Candida parapsilosis in aqueous medium

The lipase/acyltransferase from Candida parapsilosis (CpLIP2) immobilized on two synthetic resins (Accurel MP 1000 and Lewatit VP OC 1600) was used as catalyst for the production of biodiesel (fatty acid methyl esters, FAME) by transesterification of jatropha oil with methanol, in a lipid/aqueous system. The oil was dispersed in a buffer solution (pH 6.5) containing methanol in excess (2M in the biphasic system; molar ratio methanol/acyl chains 2:1). Transesterification was carried out at 30°C, under magnetic stirring, using 10% (w/w) of immobilized enzyme in relation to oil. The maximum FAME yields were attained after 8h reaction time: 80.5% and 93.8%, when CpLIP2 immobilized on Accurel MP 1000 or on Lewatit VP OC 1600 were used, respectively. CpLIP2 on both Accurel MP 1000 and Lewatit VP OC 1600 showed high operational stability along 5 consecutive 8h batches.

Dual bioimprinting of Thermomyces lanuginosus lipase for synthesis of biodiesel

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High activity TLL is made by dually bioimprinting with substrate alcohol and a surfactant.

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TLL (28 U/g of oil) bioimprinted with only the surfactants could yield 99% biodiesel from soybean oil in about 4 h.

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Dually bioimprinted TLL (only 1.4 U/g of oil) was able to yield 99% biodiesel within 48 h

Use of biodiesel as an alternative to non-renewable sources of energy has become an attractive option in recent years. The enzymatic synthesis of biodiesel by transesterification of fats/oils with an alcohol is a much more sustainable route than the chemical method. However, cost effectiveness of the enzymatic route is a major barrier in its commercialization. In this work, a high activity biocatalyst design of Thermomyces lanuginosus lipase is made by dually bioimprinting it with substrate and a surfactant (which is believed to open up the lid covering the active site of the lipase) during precipitation of the lipase in organic solvent. When the lipase was bioimprinted with only the surfactants, 28 U of the enzyme/g of oil could yield 99% biodiesel from soybean oil in about 4 h. However, when dually bioimprinted even very low enzyme load 1.4 U/g of oil, yielded 99% biodiesel within 48 h.

Consecutive lipase immobilization and glycerol carbonate production under continuous-flow conditions

Several value-added products can be produced from glycerol and among these products glycerol carbonate (GC) has received much attention in recent years because of its physical properties and wide application in the chemical, pharmaceutical and food industries.

Ultrasound intensification suppresses the need of methanol excess during the biodiesel production with Lipozyme TL-IM

The synthesis of biodiesel from sunflower oil and methanol based on transesterification using the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL-IM) has been investigated under silent conditions and under an ultrasound field. Ultrasound assisted process led to reduced processing time and requirement of lower enzyme dosage. We found for the first time that oil to methanol ratio of 1:3 was favored for the ultrasound assisted enzymatic process which is lower than that observed for the case of conventional stirring based approach (ratio of 1.4). Our results indicate that intensification provided by ultrasound suppresses the need of the excess of the methanol reactant during the enzymatic biodiesel production. Ultrasound assisted enzymatic biodiesel production is therefore a faster and a cleaner processes.

An alternative method for production of microalgal biodiesel using novel Bacillus lipase

In this study, enzymatic interesterification is carried out using encapsulated lipase as biocatalyst with methyl acetate as acyl acceptor in a solvent-free system. Lipase, isolated from a marine bacterial isolate, Bacillus sp.S23 (KF220659.1) was immobilized in sodium alginate beads. This investigation elaborated on the effects of various parameters, namely enzyme loading, temperature, water, molar ratio, reaction time and agitation for interesterification. The study resulted in the following optimal conditions: 1.5 g immobilized lipase, 1:12 molar ratio of oil to methyl acetate, 35 °C, 8 % water, 60 h reaction time, 250 rpm of agitation. With the standardized condition, the maximum conversion efficiency was 95.68 %. The immobilized beads, even after ten cycles of repeated usage showed high stability in the presence of methyl acetate and no loss of lipase activity. The microalgal biodiesel composition was analyzed using gas chromatography. The current study was efficient in using immobilized lipase for the interesterification process, since the method was cost-effective and eco-friendly, no solvent was involved and the enzyme was encapsulated in a natural polymer.

Microbial engineering for aldehyde synthesis

Aldehydes are a class of chemicals with many industrial uses. Several aldehydes are responsible for flavors and fragrances present in plants, but aldehydes are not known to accumulate in most natural microorganisms. In many cases, microbial production of aldehydes presents an attractive alternative to extraction from plants or chemical synthesis. During the past 2 decades, a variety of aldehyde biosynthetic enzymes have undergone detailed characterization. Although metabolic pathways that result in alcohol synthesis via aldehyde intermediates were long known, only recent investigations in model microbes such as Escherichia coli have succeeded in minimizing the rapid endogenous conversion of aldehydes into their corresponding alcohols. Such efforts have provided a foundation for microbial aldehyde synthesis and broader utilization of aldehydes as intermediates for other synthetically challenging biochemical classes. However, aldehyde toxicity imposes a practical limit on achievable aldehyde titers and remains an issue of academic and commercial interest. In this minireview, we summarize published efforts of microbial engineering for aldehyde synthesis, with an emphasis on de novo synthesis, engineered aldehyde accumulation in E. coli, and the challenge of aldehyde toxicity.

Sodium aluminate from waste aluminium source as catalyst for the transesterification of Jatropha oil

Transesterification of Jatropha oil with methanol is carried over heterogeneous sodium aluminate catalyst to produce biodiesel.