Interesterification of Glyceryl Trioctanoate Catalyzed by Sulfonic Silica-Based Materials: Insight into the Role of Catalysts on the Reaction Mechanism

In the present work, the acid-catalyzed interesterification of glyceryl trioctanoate (GTO) with ethyl acetate was investigated as a model reaction for the one-step production of biofuel and its additives. The activity of heterogeneous acid catalysts, such as silica-based propyl-sulfonic ones, was evaluated. Propyl-sulfonic groups were grafted on both amorphous and mesoporous silica oxide (SBA-15, KIT-6) using different functionalization processes and characterized by N₂ adsorpion-desorption isotherm (BET), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and potentiometric titration. During the optimization of the reaction conditions with the most active catalyst (Am-Pr-SO₃H), it was shown that the addition of ethanol allowed a total conversion of GTO together with 89% and 56% yield of ethyl octanoate and triacetin, respectively. The catalytic performance is strictly correlated to the catalyst features, in terms of both the acid capacity and the porous structure. Moreover, the catalytic performance is also affected by a synergistic mechanism between silanols and Pr-SO₃H groups towards the 'silanolysis' of ethyl acetate. The overall results show that the presence of ethanol, the reaction time, and the amount of catalyst shifts the reaction towards the formation of the biofuel mixture composed by ethyl octanoate and triacetin.

Sustainable Castor Bean Biodiesel Through Ricinus communis L. Lipase Extract Catalysis

The rise in oil prices, global warming, and the depletion of nonrenewable resources have led researchers to study sustainable alternatives to increasing energy demand. The autocatalysis from castor oil and castor lipases to produce biodiesel can be an excellent alternative to reduce the production costs and avoid the drawbacks of chemical transesterification. This study aimed to evaluate the catalytic activity of castor bean lipase extract (CBLE) on three vegetable oils hydrolysis, to obtain and enhance biodiesel yield by an autocatalysis from castor oil and CBLE. Furthermore, the enzymatic biodiesel physicochemical quality was analyzed. The enzymatic activity for olive oil was 76.12 U, 90.06 U for commercial castor oil, and 75.60 U in raw castor oil. The hydrolysis percentages were high at 25 °C, pH 4.5, for 4 h with 97.18% for olive oil, 98.86%, and 96.19% for commercial and raw castor oil, respectively. The CBLE catalyzed the transesterification reaction on castor oil to obtain 82.91% biodiesel yield under the selected conditions of 20% lipase loading, 1:6 oil/methanol molar ratio, and 10% buffer pH 4.5, 37 °C for 8 h. The castor biodiesel quality satisfied the ASTM-D6751 (USA) and EN-14214 (European Union) values, except for the density, viscosity, and moisture, as expected for this kind of biodiesel.

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.

RSM process optimization of biodiesel production from rapeseed oil and waste corn oil in the presence of green and novel catalyst

In the scenario of global warming and pollution, the green synthesis and use of biodiesel has acquired utmost priority. Due to several limitations of homogeneous catalysis, organobase immobilized heterogeneous catalyzed production of biodiesel has come out as a favored route. The present report demonstrates the design and synthesis of Peganum harmala spice seed extract modified GO-CuFe₂O₄ (SSE@GO-CuFe₂O₄) nanocomposite as an organobase functionalized high surface area magnetic nanocatalyst. Pistachio leaves were used in the green reduction of precursor salts to synthesize CuFe₂O₄ NPs. The as-synthesized nanomaterial was characterized physicochemically by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-Ray analysis (EDX), elemental mapping, transmission electron microscopy (TEM), X-Ray diffraction (XRD), thermogravimetric analysis (TGA) and vibrating sample magnetometer techniques (VSM). Subsequently, the catalyst was explored in the efficient synthesis of biodiesels by trans-esterification of two substrates, the rapeseed oil and waste corn oil. The optimum conditions for biodiesel production were determined through response surface methodology based on Box-Behnken design including the study of calibration curves and 3D contour plots. Easy separation and workup, use of green medium, excellent reused for several times and short reaction time are outstanding benefits of this study.

Enzyme immobilization on biomass-derived carbon materials as a sustainable approach towards environmental applications

Enzymes with their environment-friendly nature and versatility have become highly important 'green tools' with a wide range of applications. Enzyme immobilization has further increased the utility and efficiency of these enzymes by improving their stability, reusability, and recyclability. Biomass-derived matrices when used for enzyme immobilization offer a sustainable solution to environmental pollution and fuel depletion at low costs. Biochar and other biomass-derived carbon materials obtained are suitable for the immobilization of enzymes through different immobilization strategies. Environmental pollution has become an utmost topic of research interest due to an ever-increasing trend being observed in anthropogenic activities. This has widely contributed to the release of various toxic effluents into the environment in their native or metabolized forms. Therefore, more focus is being directed toward the utilization of immobilized enzymes in the bioremediation of water and soil, biofuel production, and other environmental applications. In this review, up-to-date literature concerning the immobilization and potential uses of enzymes immobilized on biomass-derived carbon materials has been presented.

Biodiesel Is Dead: Long Life to Advanced Biofuels—A Comprehensive Critical Review

Many countries are immersed in several strategies to reduce the carbon dioxide (CO2) emissions of internal combustion engines. One option is the substitution of these engines by electric and/or hydrogen engines. However, apart from the strategic and logistical difficulties associated with this change, the application of electric or hydrogen engines in heavy transport, e.g., trucks, shipping, and aircrafts, also presents technological difficulties in the short-medium term. In addition, the replacement of the current car fleet will take decades. This is why the use of biofuels is presented as the only viable alternative to diminishing CO2 emissions in the very near future. Nowadays, it is assumed that vegetable oils will be the main raw material for replacing fossil fuels in diesel engines. In this context, it has also been assumed that the reduction in the viscosity of straight vegetable oils (SVO) must be performed through a transesterification reaction with methanol in order to obtain the mixture of fatty acid methyl esters (FAMEs) that constitute biodiesel. Nevertheless, the complexity in the industrial production of this biofuel, mainly due to the costs of eliminating the glycerol produced, has caused a significant delay in the energy transition. For this reason, several advanced biofuels that avoid the glycerol production and exhibit similar properties to fossil diesel have been developed. In this way, “green diesels” have emerged as products of different processes, such as the cracking or pyrolysis of vegetable oil, as well as catalytic (hydro)cracking. In addition, some biodiesel-like biofuels, such as Gliperol (DMC-Biod) or Ecodiesel, as well as straight vegetable oils, in blends with plant-based sources with low viscosity have been described as renewable biofuels capable of performing in combustion ignition engines. After evaluating the research carried out in the last decades, it can be concluded that green diesel and biodiesel-like biofuels could constitute the main alternative to addressing the energy transition, although green diesel will be the principal option in aviation fuel.

Sustainable biodiesel generation through catalytic transesterification of waste sources: a literature review and bibliometric survey

Sustainable renewable energy production is being intensely disputed worldwide because fossil fuel resources are declining gradually. One solution is biodiesel production via the transesterification process, which is environmentally feasible due to its low-emission diesel substitute. Significant issues arising with biodiesel production are the cost of the processes, which has stuck its sustainability and the applicability of different resources. In this article, the common biodiesel feedstock such as edible and non-edible vegetable oils, waste oil and animal fats and their advantages and disadvantages were reviewed according to the Web of Science (WOS) database over the timeframe of 1970–2020. The biodiesel feedstock has water or free fatty acid, but it will produce soap by reacting free fatty acids with an alkali catalyst when they present in high portion. This reaction is unfavourable and decreases the biodiesel product yield. This issue can be solved by designing multiple transesterification stages or by employing acidic catalysts to prevent saponification. The second solution is cheaper than the first one and even more applicable because of the abundant source of catalytic materials from a waste product such as rice husk ash, chicken eggshells, fly ash, red mud, steel slag, and coconut shell and lime mud. The overview of the advantages and disadvantages of different homogeneous and heterogeneous catalysts is summarized, and the catalyst promoters and prospects of biodiesel production are also suggested. This research provides beneficial ideas for catalyst synthesis from waste for the transesterification process economically, environmentally and industrially.

Sustainable renewable energy production is being intensely disputed worldwide because fossil fuel resources are declining gradually.

An overview to process design, simulation and sustainability evaluation of biodiesel production

The overwhelming concerns due to over exploitation of fossil resources necessitate the utilization of alternative energy resources. Biodiesel has been considered as one of the most adaptable alternative to fossil-derived diesel with similar properties and numerous environmental benefits. Although there are various approaches for biodiesel production, development of cost-effective and robust catalyst with efficient production methods and utilization of a variety of feedstock could be the optimum solution to bring down the production cost. Considering the complexity of biodiesel production processes, process design, quantitative evaluation and optimization of the biodiesel from whole systems perspectives is essential for unlocking the complexity and enhancing the system performances. Process systems engineering offers an efficient approach to design and optimize biodiesel manufacturing systems by using a variety of tools. This review reflects state-of-the-art biodiesel research in the field of process systems engineering with a particular focus on biodiesel production including process design and simulation, sustainability evaluation, optimization and supply chain management. This review also highlights the challenges and opportunities for the development of potentially sustainable and eco-friendly enzymatic biodiesel technology.

Identification of functional cytochrome P450 and ferredoxin from Streptomyces sp. EAS-AB2608 by transcriptional analysis and their heterologous expression

Bioconversion using microorganisms and their enzymes is an important tool in many industrial fields. The discovery of useful new microbial enzymes contributes to the development of industries utilizing bioprocesses. Streptomyces sp. EAS-AB2608, isolated from a soil sample collected in Japan, can convert the tetrahydrobenzotriazole CPD-1 (a selective positive allosteric modulator of metabotropic glutamate receptor 5) to its hydroxylated form at the C4-(R) position. The current study was performed to identify the genes encoding the enzymes involved in CPD-1 bioconversion and to verify their function. To identify gene products responsible for the conversion of CPD-1, we used RNA sequencing to analyze EAS-AB2608; from its 8333 coding sequences, we selected two genes, one encoding cytochrome P450 (easab2608_00800) and the other encoding ferredoxin (easab2608_00799), as encoding desirable gene products involved in the bioconversion of CPD-1. The validity of this selection was tested by using a heterologous expression approach. A bioconversion assay using genetically engineered Streptomyces avermitilis SUKA24 ∆saverm3882 ∆saverm7246 co-expressing the two selected genes (strain ES_SUKA_63) confirmed that these gene products had hydroxylation activity with respect to CPD-1, indicating that they are responsible for the conversion of CPD-1. Strain ES_SUKA_63 also showed oxidative activity toward other compounds and therefore might be useful not only for bioconversion of CPD-1 but also as a tool for synthesis of drug metabolites and in optimization studies of various pharmaceutical lead compounds. We expect that this approach will be useful for bridging the gap between the latest enzyme optimization technologies and conventional enzyme screening using microorganisms. KEY POINTS: • Genes easab2608_00800 (cyp) and easab2608_00799 (fdx) were selected by RNA-Seq. • Selection validity was evaluated by an engineered S. avermitilis expression system. • Strain ES_SUKA_63 showed oxidative activity toward CPD-1 and other compounds.

Newer Non-ionic A2 B2 -Type Enzyme-Responsive Amphiphiles for Drug Delivery

A new series of nonionic gemini amphiphiles have been synthesized in a multi-step chemoenzymatic approach by using a novel A₂ B₂ -type central core consisting of conjugating glycerol and propargyl bromide on 5-hydroxy isophthalic acid. A pair of hydrophilic monomethoxy poly(ethylene glycol) (mPEG) and hydrophobic linear alkyl chains (C₁₂ /C₁₅ ) were then added to the core to obtain amphiphilic architectures. The aggregation tendency in aqueous media was studied by dynamic light scattering, fluorescence spectroscopy and cryogenic transmission electron microscopy. The nanotransport potential of the amphiphiles was studied for model hydrophobic guests, that is, the dye Nile Red and the drug Nimodipine by using UV/Vis and fluorescence spectroscopy. Evaluation of the viability of amphiphile-treated A549 cells showed them to be well tolerated up to the concentrations studied. Being ester based, these amphiphiles exhibit stimuli-responsive sensitivity towards esterases, and a rupture of amphiphilic architecture was observed in the presence of immobilized Candida antarctica lipase (Novozym 435), thus facilitating release of the encapsulated guest from the aggregate.

Covalent immobilization of lipase from Candida rugosa on epoxy-activated cloisite 30B as a new heterofunctional carrier and its application in the synthesis of banana flavor and production of biodiesel

In this paper, an epoxy-activated cloisite (ECL) was prepared as a new heterofunctional carrier via a reaction between cloisite 30B (CL) and epichlorohydrin and utilized for covalent immobilization of lipase from Candida rugosa. The lipase immobilized on the ECL (LECL) was successfully used in the olive oil hydrolysis, synthesis of isoamyl acetate (banana flavor), and biodiesel production. The TGA, FT-IR, SEM, and XRD were used to characterize CL, ECL, and LECL. The influences of temperature, pH, thermal stability, and storage capacity were examined in the olive oil hydrolysis. The effects of solvent, temperature, time, water content, and substrates molar ratio on the yields of ester and biodiesel were also investigated. In the optimized conditions, the hydrolytic activity of LECL was 1.85 ± 0.05 U/ mg, and the maximum yield of ester and biodiesel was 91.6% and 95.4%, respectively. The LECL showed good thermal stability and storage capacity compared to the free lipase. Additionally, LECL was reusable for both esterification and transesterification after being used for nine cycles.

Transesterification of rapeseed oil and waste corn oil toward the production of biodiesel over a basic high surface area magnetic nanocatalyst: application of the response surface methodology in process optimization

A new, green, and recoverable catalyst is prepared for the synthesis of biodiesel.

Tailoring Particle-Enzyme Nanoconjugates for Biocatalysis at the Organic-Organic Interface

Nonaqueous Pickering emulsions (PEs) are a powerful platform for catalysis design, offering both a large interface contact and a preferable environment for water-sensitive synthesis. However, up to now, little progress has been made to incorporate insoluble enzymes into the nonaqueous system for biotransformation. Herein, we present biocatalytically active nonaqueous PEs, stabilized by particle-enzyme nanoconjugates, for the fast transesterification and esterification, and eventually for biodiesel synthesis. Our nanoconjugates are the hybrid biocatalysts tailor-made by loading hydrophilic Candida antarctica lipase B onto hydrophobic silica nanoparticles, resulting in not only catalytically active but highly amphiphilic particles for stabilization of a methanol-decane emulsion. The enzyme activity in these PEs is significantly enhanced, ca. 375-fold higher than in the nonaqueous biphasic control. Moreover, the PEs can be multiply reused without significant loss of enzyme performance. With this proof-of-concept, this system can be expanded for many advanced syntheses using different enzymes in the future.

Preparation of Immobilized Lipase on Silica Clay as a Potential Biocatalyst on Synthesis of Biodiesel

Biodiesel offers an important alternative to fossil fuel. In this work, Eversa Transform 2.0 lipase was immobilized onto 3-aminopropyltriethoxysilane (APTES) modified silica clay (SC) by glutaraldehyde. The characteristics of the functionalized supports and the immobilized lipase were investigated by FTIR, TEM, BET, and XRD. The results show that the optimal conditions of lipase immobilization are as follows: 2% glutaraldehyde concentration, 15 mg/mL lipase concentration and incubating at 25 °C for 60 min. The immobilized lipase showed a high tolerance to temperature and pH variation in comparison to the free lipase. The immobilized lipase on SC was applied as a biocatalyst for the synthesis of biodiesel from methanol and canola oil. A biodiesel yield of 86% was obtained at a temperature of 45 °C via a three-step methanol addition. A conversion yield of 67% was maintained after reusing the immobilized lipase for five cycles. This work provides a strategy for the preparation of an efficient biocatalyst for the synthesis of biodiesel.

Sustainable Production of Microbial Isoprenoid Derived Advanced Biojet Fuels Using Different Generation Feedstocks: A Review

As the fastest mode of transport, the aircraft is a major driver for globalization and economic growth. The development of alternative advanced liquid fuels is critical to sustainable development within the sector. Such fuels should be compatible with existing infrastructure and derived from second generation feedstocks to avoid competition with food markets. With properties similar to petroleum based fuels, isoprenoid derived compounds such as limonene, bisabolane, farnesane, and pinene dimers are of increasing interest as "drop-in" replacement jet fuels. In this review potential isoprenoid derived jet fuels and progress toward their microbial production was discussed in detail. Although substantial advancements have been achieved, the use of first generation feedstocks remains ubiquitous. Lignocellulosic biomass is the most abundant raw material available for biofuel production, however, technological constraints associated with its pretreatment and saccharification hinder its economic feasibility for low-value commodity production. Non-conventional microbes with novel characteristics including cellulolytic bacteria and fungi capable of highly efficient lignocellulose degradation and xylose fermenting oleaginous yeast with enhanced lignin-associated inhibitor tolerance were investigated as alternatives to traditional model hosts. Finally, innovative bioprocessing methods including consolidated bioprocessing and sequential bioreactor approaches, with potential to capitalize on such unique natural capabilities were considered.

Microbial lipases and their industrial applications: a comprehensive review

Lipases are very versatile enzymes, and produced the attention of the several industrial processes. Lipase can be achieved from several sources, animal, vegetable, and microbiological. The uses of microbial lipase market is estimated to be USD 425.0 Million in 2018 and it is projected to reach USD 590.2 Million by 2023, growing at a CAGR of 6.8% from 2018. Microbial lipases (EC 3.1.1.3) catalyze the hydrolysis of long chain triglycerides. The microbial origins of lipase enzymes are logically dynamic and proficient also have an extensive range of industrial uses with the manufacturing of altered molecules. The unique lipase (triacylglycerol acyl hydrolase) enzymes catalyzed the hydrolysis, esterification and alcoholysis reactions. Immobilization has made the use of microbial lipases accomplish its best performance and hence suitable for several reactions and need to enhance aroma to the immobilization processes. Immobilized enzymes depend on the immobilization technique and the carrier type. The choice of the carrier concerns usually the biocompatibility, chemical and thermal stability, and insolubility under reaction conditions, capability of easy rejuvenation and reusability, as well as cost proficiency. Bacillus spp., Achromobacter spp., Alcaligenes spp., Arthrobacter spp., Pseudomonos spp., of bacteria and Penicillium spp., Fusarium spp., Aspergillus spp., of fungi are screened large scale for lipase production. Lipases as multipurpose biological catalyst has given a favorable vision in meeting the needs for several industries such as biodiesel, foods and drinks, leather, textile, detergents, pharmaceuticals and medicals. This review represents a discussion on microbial sources of lipases, immobilization methods increased productivity at market profitability and reduce logistical liability on the environment and user.

Enzymatic transesterification of coconut oil by using immobilized lipase on biochar: An experimental and molecular docking study

Guava seed biochar appears as a new alternative of the effective support to the immobilization of Burkholderia cepacia lipase (BCL) by physical adsorption. The objective of this work was to evaluate the potential of this immobilized biocatalyst in the transesterification reaction of crude coconut oil and ethanol and to understand the mechanism of the reaction through the study of molecular docking. The best loading of BCL was determined to be 0.15 g_enzyme /g_support having a hydrolytic activity of 260 U/g and 54% immobilization yield. The products of transesterification reaction produced a maximum yield at 40 °C under different reaction conditions. The monoacylglycerols (MAGs) conversion of 59% was using substrate molar ratio oil:ethanol of 1:7 with the reaction time of 24 H. In addition, the highest ethyl esters yield (48%) had the molar ratio of 1:7 with the reaction time of 96 H and maximum conversion of diacylglycerols (DAGs) was 30% with the molar ratio of 1:6 with the reaction time of 24 H. Molecular Docking was applied to clarify the mechanisms of transesterification reaction at the molecular level. MAGs and DAGs are compounds with excellent emulsifying properties used in industrial production of several bioproducts such as cosmetic, pharmaceuticals, foods, and lubricants.

On the donor substrate dependence of group-transfer reactions by hydrolytic enzymes: Insight from kinetic analysis of sucrose phosphorylase-catalyzed transglycosylation

Chemical group-transfer reactions by hydrolytic enzymes have considerable importance in biocatalytic synthesis and are exploited broadly in commercial-scale chemical production. Mechanistically, these reactions have in common the involvement of a covalent enzyme intermediate which is formed upon enzyme reaction with the donor substrate and is subsequently intercepted by a suitable acceptor. Here, we studied the glycosylation of glycerol from sucrose by sucrose phosphorylase (SucP) to clarify a peculiar, yet generally important characteristic of this reaction: partitioning between glycosylation of glycerol and hydrolysis depends on the type and the concentration of the donor substrate used (here: sucrose, α-d-glucose 1-phosphate (G1P)). We develop a kinetic framework to analyze the effect and provide evidence that, when G1P is used as donor substrate, hydrolysis occurs not only from the β-glucosyl-enzyme intermediate (E-Glc), but additionally from a noncovalent complex of E-Glc and substrate which unlike E-Glc is unreactive to glycerol. Depending on the relative rates of hydrolysis of free and substrate-bound E-Glc, inhibition (Leuconostoc mesenteroides SucP) or apparent activation (Bifidobacterium adolescentis SucP) is observed at high donor substrate concentration. At a G1P concentration that excludes the substrate-bound E-Glc, the transfer/hydrolysis ratio changes to a value consistent with reaction exclusively through E-Glc, independent of the donor substrate used. Collectively, these results give explanation for a kinetic behavior of SucP not previously accounted for, provide essential basis for design and optimization of the synthetic reaction, and establish a theoretical framework for the analysis of kinetically analogous group-transfer reactions by hydrolytic enzymes.

Composites of Crosslinked Aggregates of Eversa® Transform and Magnetic Nanoparticles. Performance in the Ethanolysis of Soybean Oil

Eversa® Transform 2.0 has been launched to be used in free form, but its immobilization may improve its performance. This work aimed to optimize the immobilization of Eversa® Transform 2.0 by the crosslinked enzyme aggregates (CLEAs) technique, using almost all the available tools to improve its performance. Several variables in the CLEA preparation were optimized to improve the recovered activity, such as precipitant nature and crosslinker concentration. Moreover, some feeders were co-precipitated to improve the crosslinking step, such as bovine serum albumin, soy protein, or polyethyleneimine. Starch (later enzymatically degraded) was utilized as a porogenic agent to decrease the substrate diffusion limitations. Silica magnetic nanoparticles were also utilized to simplify the CLEA handling, but it was found that a large percentage of the Eversa activity could be immobilized on these nanoparticles before aggregation. The best CLEA protocol gave a 98.9% immobilization yield and 30.1% recovered activity, exhibited a porous structure, and an excellent performance in the transesterification of soybean oil with ethanol: 89.8 wt% of fatty acid ethyl esters (FAEEs) yield after 12 h of reaction, while the free enzyme required a 48 h reaction to give the same yield. A caustic polishing step of the product yielded a biodiesel containing 98.9 wt% of FAEEs and a free fatty acids content lower than 0.25%, thus the final product met the international standards for biodiesel. The immobilized biocatalyst could be reused for at least five 12 h-batches maintaining 89.6% of the first-batch yield, showing the efficient catalyst recovery by applying an external magnetic field.

A Novel Fungal Lipase With Methanol Tolerance and Preference for Macaw Palm Oil

Macaw palm is a highly oil-producing plant, which presents high contents of free fatty acids, being a promising feedstock for biofuel production. The current chemical routes are costly and complex, involving highly harsh industrial conditions. Enzymatic processing is a potential alternative; however, it is hampered by the scarce knowledge on biocatalysts adapted to this acidic feedstock. This work describes a novel lipase isolated from the thermophilic fungus Rasamsonia emersonii (ReLip), which tolerates extreme conditions such as the presence of methanol, high temperatures, and acidic medium. Among the tested feedstocks, the enzyme showed the highest preference for macaw palm oil, producing a hydrolyzate with a final free fatty acid content of 92%. Crystallographic studies revealed a closed conformation of the helical amphipathic lid that typically undergoes conformational changes in a mechanism of interfacial activation. Such conformation of the lid is stabilized by a salt bridge, not observed in other structurally characterized homologs, which is likely involved in the tolerance to organic solvents. Moreover, the lack of conservation of the aromatic cluster IxxWxxxxxF in the lid of ReLip with the natural mutation of the phenylalanine by an alanine might be correlated with the preference of short acyl chains, although preserving catalytic activity on insoluble substrates. In addition, the presence of five acidic amino acids in the lid of ReLip, a rare property reported in other lipases, may have contributed to its ability to tolerate and be effective in acidic environments. Therefore, our work describes a new fungal biocatalyst capable of efficiently hydrolyzing macaw oil, an attractive feedstock for the production of "drop-in" biofuels, with high desirable feature for industrial conditions such as thermal and methanol tolerance, and optimum acidic pH. Moreover, the crystallographic structure was elucidated, providing a structural basis for the enzyme substrate preference and tolerance to organic solvents.

Stereoselective Synthesis of Terpenoids through Lipase-Mediated Resolution Approaches

This review article focuses on the scientific developments concerning the lipase-mediated synthesis of terpenoids that have been reported in the literature during the last twenty years. More specifically, this review describes in depth the resolution approaches that allow the preparation of the chiral building blocks used for the stereoselective synthesis of bioactive terpenoids. The synthetic methods that have given new and innovative perspectives from a scientific standpoint, and the preparative approaches that possess industrial importance, are described thoroughly.

Optimization of the Production of Enzymatic Biodiesel from Residual Babassu Oil (Orbignya sp.) via RSM

Residual oil from babassu (Orbignya sp.), a low-cost raw material, was used in the enzymatic esterification for biodiesel production, using lipase B from Candida antarctica (Novozym® 435) and ethanol. For the first time in the literature, residual babassu oil and Novozym® 435 are being investigated to obtain biodiesel. In this communication, response surface methodology (RSM) and a central composite design (CCD) were used to optimize the esterification and study the effects of four factors (molar ratio (1:1–1:16, free fatty acids (FFAs) /alcohol), temperature (30–50 °C), biocatalyst content (0.05–0.15 g) and reaction time (2–6 h)) in the conversion into fatty acid ethyl esters. Under optimized conditions (1:18 molar ratio (FFAs/alcohol), 0.14 g of Novozym® 435, 48 °C and 4 h), the conversion into ethyl esters was 96.8%. It was found that after 10 consecutive cycles of esterification under optimal conditions, Novozym® 435 showed a maximum loss of activity of 5.8%, suggesting a very small change in the support/enzyme ratio proved by Fourier Transform Infrared (FTIR) spectroscopy and insignificant changes in the surface of Novozym® 435 proved by scanning electron microscopy (SEM) after the 10 consecutive cycles of esterification.

Biodiesel at the Crossroads: A Critical Review

The delay in the energy transition, focused in the replacement of fossil diesel with biodiesel, is mainly caused by the need of reducing the costs associated to the transesterification reaction of vegetable oils with methanol. This reaction, on an industrial scale, presents several problems associated with the glycerol generated during the process. The costs to eliminate this glycerol have to be added to the implicit cost of using seed oil as raw material. Recently, several alternative methods to convert vegetable oils into high quality diesel fuels, which avoid the glycerol generation, are being under development, such as Gliperol, DMC-Biod, or Ecodiesel. Besides, there are renewable diesel fuels known as “green diesel”, obtained by several catalytic processes (cracking or pyrolysis, hydrodeoxygenation and hydrotreating) of vegetable oils and which exhibit a lot of similarities with fossil fuels. Likewise, it has also been addressed as a novel strategy, the use of straight vegetable oils in blends with various plant-based sources such as alcohols, vegetable oils, and several organic compounds that are renewable and biodegradable. These plant-based sources are capable of achieving the effective reduction of the viscosity of the blends, allowing their use in combustion ignition engines. The aim of this review is to evaluate the real possibilities that conventional biodiesel has in order to success as the main biofuel for the energy transition, as well as the use of alternative biofuels that can take part in the energy transition in a successful way.

Lipase Production by Solid-State Cultivation of Thermomyces Lanuginosus on By-Products from Cold-Pressing Oil Production

This study shows that by-products obtained after cold-pressing oil production (flex oil cake, hemp oil cake, hull-less pumpkin oil cake) could be used as substrates for the sustainable and cost-effective production of lipase when cultivating Thermomyces lanuginosus under solid-state conditions (T = 45 °C, t = 9 days). Lipase showed optimum activity at T = 40 °C. The produced lipase extract was purified 17.03-folds with a recovery of 1% after gel chromatography. Three different batch experiments were performed in order to test the possibility of using the lipase in biodiesel production. Experiments were performed with a commercial, unpurified enzyme, and partially purified lipase with sunflower oil and methanol as substrates in a batch reactor at 40 °C. During the experiments, the operational stability of the enzyme was studied. The obtained results clearly showed that produced crude and purified lipase can be used for biodiesel production, but the process needs some additional optimization. As for operation stability, it was noticed that the commercial enzyme was deactivated after 30 h, while produced crude enzyme remained 8.25% of its activity after 368 h.

Novel Combi-lipase Systems for Fatty Acid Ethyl Esters Production

Most Combi-lipases (CL) are based on mixtures of different lipases immobilized on different supports. The increased CL efficiency has been attributed solely to the complementary selectivity of lipases. However, the role of the immobilization support in CL or in co-immobilized systems (coCL) and the application of kinetic models to account CL composition effects, have not been assessed. In this work, commercial lipases from Thermomyces lunuginosus (TLL), Candida antarctica (CALB) and Rhizomocur miehei (RML) and supports as Lewatit®VPOC1600 (LW) and Purolite®ECR1604 (PU), were combined to produce new CL systems for the production of fatty acid ethyl esters (EE) which are the main component of ethylic biodiesel: Co-immobilization slightly altered palm olein EE yields with regard to that of equivalent CL systems, e.g., the best coCL of TLL and CALB in LW (89.5%) and the respective CL (81.8%). The support did affect CL behavior: (i) The best coCL of TLL and RML on LW produced 80.0% EE while on PU 76.4%; (ii) CL based on mixtures of the same enzyme, but immobilized on different supports (semiCL) show complementarity: The best TLL semiCL produced 86.1% EE while its constituents (LW) and (PU) produced individually 78.2 and 70.3%, respectively. The proposed model accounts adequately the EE production properties for CL systems based on TLL, CALB and LW. This work expands the tools to obtain new CL systems for EE production.

A fluorescence-based activity assay for immobilized lipases in non-native media

A new method for the analysis of lipase activity in the immobilized state is developed. The fluorescence assay aims to quantify the potential of lipases for the application in organic solvents. As lipases are universally immobilized on polymeric carriers for the use in bioorganic synthesis, the assay includes an immobilization step on the walls of polymeric cuvettes. The activity of the immobilized lipase is probed by 4-methylumbelliferyl ester hydrolysis. The activity retention as a function of solvent concentration is used as a measure for the solvent resistance of the enzyme variant. The method is applied to two different lipases, Candida antarctica lipase B (CalB) and Bacillus subtilis lipase A (BSLA) in the presence of the solvents acetonitrile and ethanol. By comparison of the assay results with a commercial biocatalyst consisting of CalB on polymeric carrier (Novozyme 435) it is demonstrated that the assay allows a good prediction of the activity of the respective lipase as immobilisate on polymeric carriers. The assay surpasses the respective analysis in solution in terms of accuracy and precision.

Probing the Catalytic Efficiency of Supported Heteropoly Acids for Esterification: Effect of Weak Catalyst Support Interactions

Supported heteropoly acids are an interesting class of solid acid catalysts which possess flexible structure and super acidic properties essentially required for the oil-based biodiesel production. In this study, a series of catalysts containing 25 wt.% of heteropolytungstate (HPW) supported on various clays or SiO2 were prepared, and their catalytic efficiency was evaluated for esterification of acetic acid with heptanol. The as-prepared catalysts were characterized by various techniques including FT-IR spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and BET. The catalytic efficiency of both bulk and supported HPW catalysts for the esterification activity strongly depends on the type of support and amount of catalyst; the bulk HPW catalyst and the catalyst supported by kaolinite with 25 wt.% of HPW exhibited highest activity. In order to study the effect of temperature on conversion, all the catalysts were subjected to different reaction temperatures. It was revealed that esterification activity of both bulk and supported HPW catalysts strongly depends upon the temperature variations of the reaction. Besides, the effect of leaching of active sites on the catalysts performance for biodiesel production was also evaluated by inductively coupled plasma studies (ICP). The kaolinite-supported catalyst (25% HPW/kaolinite) demonstrated higher amount of leaching which is also confirmed by the significant decrease in its catalytic activity when it is used for the second time. However, the higher activity demonstrated by HPW/kaolinite maybe because of some homogeneous reaction indicating a weak catalyst support interaction (WCSI) resulting in the leaching of the catalyst during the test. Furthermore, the effects of other reaction variables such as catalyst loading and reaction time on the conversion of acetic acid were also studied.

Biodiesel Production via Trans-Esterification Using Pseudomonas cepacia Immobilized on Cellulosic Polyurethane

In this work, Pseudomonas cepacia lipase immobilized on cellulosic polyurethane was used as a catalyst for biodiesel production via trans-esterification reactions in order to provide cost-effective methods of enzyme recycling. The efficacy of the immobilized enzyme catalyst at low loading (6.2 wt %) and the effects of temperature, water content, and reaction time in model trans-esterification of glyceryl trioctanoate were investigated extensively. It was found that water was necessary for the reaction of glyceryl trioctanoate with ethanol to proceed. A high conversion of glyceryl trioctanoate (∼70%) was obtained at 35 °C, with only 5.0 wt % of water content over a reaction period of 12 h.

An Organic Solvent-Tolerant Lipase with Both Hydrolytic and Synthetic Activities from the Oleaginous Fungus Mortierella echinosphaera

Lipase enzymes of the oleaginous fungal group Mortierella are rarely studied. However, considering that most commercial lipases are derived from filamentous fungal sources, their investigation can contribute to the cost-effective development of new biotechnological processes. Here, an extracellular lipase with a molecular mass of 30 kDa was isolated from Mortierella echinosphaera CBS 575.75 and characterized. The purified lipase exhibited an optimal p-nitrophenyl palmitate (pNPP)-hydrolyzing activity at 25 °C and pH 6.6-7.0 and proved to be highly stable at temperatures up to 40 °C and under broad pH conditions. The enzyme was active under low temperatures, retaining 32.5% of its activity at 10 °C, and was significantly stable in polar and non-polar organic solvents. The Km, Vmax, and kcat for pNPP were 0.336 mM, 30.4 μM/min, and 45.7 1/min for pNPP and 0.333 mM, 36.9 μM/min, and 55.6 1/min for pNP-decanoate, respectively. The pNPP hydrolysis was inhibited by Hg2+, N-bromosuccinimide, and sodium dodecyl sulfate, while ethylenediaminetetraacetic acid and metal ions, such as Ca2+, Mg2+, Na⁺, and K⁺ enhanced the activity. The purified lipase had non-regioselective activity and wide substrate specificity, showing a clear preference for medium-chained p-nitrophenyl esters. Besides its good transesterification activity, the enzyme appeared as a suitable biocatalyst to operate selective esterification reactions to long-chained alkyl esters. Adsorption to Accurel MP1000 improved the storage stability of the enzyme at 5 °C. The immobilized lipase displayed tolerance to a non-aqueous environment and was reusable for up to five cycles without significant loss in its synthetic and hydrolytic activities. These findings confirm the applicability of both the free and the immobilized enzyme preparations in future research.

Enzymatic Production of Biodiesel: Strategies to Overcome Methanol Inactivation

Lipase-catalyzed transesterification of triglycerides and alcohols to obtain biodiesel is an environmentally friendly and sustainable route for fuels production since, besides proceeding in mild reaction conditions, it allows for the use of low-cost feedstocks that contain water and free fatty acids, for example non-edible oils and waste oils. This review article reports recent advances in the field and focus in particular on a major issue in the enzymatic process, the inactivation of most lipases caused by methanol, the preferred acyl acceptor used for alcoholysis. The recent results about immobilization of enzymes on nano-materials and the use of whole-cell biocatalysts, as well as the use of cell-surface display technologies and metabolic engineering strategies for microbial production of biodiesel are described. It is discussed also insight into the effects of methanol on lipases obtained by modeling approaches and report on studies aimed at mining novel alcohol stable enzymes or at improving robustness in existing ones by protein engineering.

Supported ionic liquid phase (SILP) facilitated gas-phase enzyme catalysis – CALB catalyzed transesterification of vinyl propionate

The supported ionic liquid phase (SILP) technology has been used to immobilize Candida Antarctica Lipase B (CALB) within a hybrid monolith.

Lipases: An Overview

Lipases are ubiquitous enzymes, widespread in nature. They were first isolated from bacteria in the early nineteenth century, and the associated research continuously increased due to the characteristics of these enzymes. This chapter reviews the main sources, structural properties, and industrial applications of these highly studied enzymes.

New Strategy for the Immobilization of Lipases on Glyoxyl-Agarose Supports: Production of Robust Biocatalysts for Natural Oil Transformation

Immobilization on Glyoxyl–agarose support (Gx) is one of the best strategies to stabilize enzymes. However, the strategy is difficult to apply at neutral pH when most enzymes are stable and, even when possible, produces labile derivatives. This work contributes to overcoming this hurdle through a strategy that combines solid-phase amination, presence of key additives, and derivative basification. To this end, aminated industrial lipases from Candida artarctica (CAL), Thermomyces lunuginosus (TLL), and the recombinant Geobacillus thermocatenulatus (BTL2) were immobilized on Gx for the first time at neutral pH using anthranilic acid (AA) or DTT as additives (immobilization yields >70%; recovered activities 37.5–76.7%). The spectroscopic evidence suggests nucleophilic catalysis and/or adsorption as the initial lipase immobilization events. Subsequent basification drastically increases the stability of BTL2–glyoxyl derivatives under harsh conditions (t_1/2, from 2.1–54.5 h at 70 °C; from 10.2 h–140 h in 80% dioxane). The novel BTL2-derivatives were active and selective in fish oil hydrolysis (1.0–1.8 μmol of polyunsaturated fatty acids (PUFAs) min⁻¹·g⁻¹) whereas the selected TLL-derivative was as active and stable in biodiesel production (fatty ethyl esters, EE) as the commercial Novozyme^®-435 after ten reaction cycles (~70% EE). Therefore, the potential of the proposed strategy in producing suitable biocatalysts for industrial processes was demonstrated.

Facile one-pot fabrication of cellulose nanocrystals and enzymatic synthesis of its esterified derivative in mixed ionic liquids

As an important cellulose derivative, esterified cellulose nanocrystals (E-CNCs) could be applied in biomedical and chemical industries.

Synthesis of magnetic carbonaceous acids derived from hydrolysates of Jatropha hulls for catalytic biodiesel production

Magnetic carbonaceous acid derived from Jatropha hulls achieved 96.5% biodiesel yield with catalyst recovery of 94.3% in 5-cycle uses.