How lipase technology contributes to evolution of biodiesel production using multiple feedstocks

A review of nanotechnology in enzyme cascade to address challenges in pre-treating biomass

Nanotechnology has become a revolutionary technique for improving the preliminary treatment of lignocellulosic biomass in the production of biofuels. Traditional methods of pre-treatment have encountered difficulties in effectively degrading the intricate lignocellulosic composition, thereby impeding the conversion of biomass into fermentable sugars. Nanotechnology has enabled the development of enzyme cascade processes that present a potential solution for addressing the limitations. The focus of this review article is to delve into the utilization of nanotechnology in the pretreatment of lignocellulosic biomass through enzyme cascade processes. The review commences with an analysis of the composition and structure of lignocellulosic biomass, followed by a discussion on the drawbacks associated with conventional pre-treatment techniques. The subsequent analysis explores the importance of efficient pre-treatment methods in the context of biofuel production. We thoroughly investigate the utilization of nanotechnology in the pre-treatment of enzyme cascades across three distinct sections. Nanomaterials for enzyme immobilization, enhanced enzyme stability and activity through nanotechnology, and nanocarriers for controlled enzyme delivery. Moreover, the techniques used to analyse nanomaterials and the interactions between enzymes and nanomaterials are introduced. This review emphasizes the significance of comprehending the mechanisms underlying the synergy between nanotechnology and enzymes establishing sustainable and environmentally friendly nanotechnology applications.

The effects of the chemical modification on immobilized lipase features are affected by the enzyme crowding in the support

In this article, we have analyzed the interactions between enzyme crowding on a given support and its chemical modification (ethylenediamine modification via the carbodiimide route and picryl sulfonic (TNBS) modification of the primary amino groups) on the enzyme activity and stability. Lipase from Thermomyces lanuginosus (TLL) and lipase B from Candida antarctica (CALB) were immobilized on octyl-agarose beads at two very different enzyme loadings, one of them exceeding the capacity of the support, one well under this capacity. Chemical modifications of the highly loaded and lowly loaded biocatalysts gave very different results in terms of activity and stability, which could increase or decrease enzyme activity depending on the enzyme support loading. For example, both lowly loaded biocatalysts increased their activity after modification while the effect was the opposite for the highly loaded biocatalysts. Additionally, the modification with TNBS of highly loaded CALB biocatalyst increased its stability while decrease the activity.

Rapid prediction method of ZIF-8 immobilized Candida rugosa lipase activity by near-infrared spectroscopy

Candida rugosa lipase (CRL, EC3.1.1.3) is one of the main enzymes synthesizing esters, and ZIF-8 was chosen as an immobilization carrier for lipase. Enzyme activity testing often requires expensive reagents as substrates, and the experiment processes are time-consuming and inconvenient. As a result, a novel approach based on near-infrared spectroscopy (NIRs) was developed for predicting CRL/ZIF-8 enzyme activity. The absorbance of the immobilized enzyme catalytic system was evaluated using UV-Vis spectroscopy to investigate the amount of CRL/ZIF-8 enzyme activity. The powdered samples' near-infrared spectra were obtained. The sample's enzyme activity data were linked with each sample's original NIR spectra to establish the NIR model. A partial least squares (PLS) model of immobilized enzyme activity was developed by coupling spectral preprocessing with a variable screening technique. The experiments were completed within 48 h to eliminate inaccuracies between the reduction in enzyme activity with increasing laying-aside time throughout the test and the NIRs modeling. The root-mean-square error of cross-validation (RMSECV), the correlation coefficient of validation set (R) value, and the ratio of prediction to deviation (RPD) value were employed as assessment model indicators. The near-infrared spectrum model was developed by merging the best 2nd derivative spectral preprocessing with the Competitive Adaptive Reweighted Sampling (CARS) variable screening method. This model's root-mean-square error of cross-validation (RMSECV) was 0.368 U/g, the correlation coefficient of calibration set (R_cv) value was 0.943, the root-mean-square error of prediction (RMSEP) set was 0.414 U/g, the correlation coefficient of validation set (R) value was 0.952, and the ratio of prediction to deviation (RPD) was 3.0. The model demonstrates that the fitting relationship between the predicted and the reference enzyme activity value of the NIRs is satisfactory. The findings revealed a strong relationship between NIRs and CRL/ZIF-8 enzyme activity. As a result, the established model could be implemented to quantify the enzyme activity of CRL/ZIF-8 quickly by including more variations of natural samples. The prediction method is simple, rapid, and adaptable to be the theoretical and practical basis for further studying other interdisciplinary research work in enzymology and spectroscopy.

Biocatalytic production of biolubricants: Strategies, problems and future trends

The increasing worries by the inadequate use of energy and the preservation of nature are promoting an increasing interest in the production of biolubricants. After discussing the necessity of producing biolubricants, this review focuses on the production of these interesting molecules through the use of lipases, discussing the different possibilities (esterification of free fatty acids, hydroesterification or transesterification of oils and fats, transesterification of biodiesel with more adequate alcohols, estolides production, modification of fatty acids). The utilization of discarded substrates has special interest due to the double positive ecological impact (e.g., oil distillated, overused oils). Pros and cons of all these possibilities, together with general considerations to optimize the different processes will be outlined. Some possibilities to overcome some of the problems detected in the production of these interesting compounds will be also discussed.

Recent Advances in Overexpression of Functional Recombinant Lipases

Heterologous functional expression of the recombinant lipases is typically a bottleneck due to the expression in the insoluble fraction as inclusion bodies (IBs) which are in inactive form. Due to the importance of lipases in various industrial applications, many investigations have been conducted to discover suitable approaches to obtain functional lipase or increase the expressed yield in the soluble fraction. The utilization of the appropriate prokaryotic and eukaryotic expression systems, along with the suitable vectors, promoters, and tags, has been recognized as a practical approach. One of the most powerful strategies to produce bioactive lipases is using the molecular chaperones co-expressed along with the target protein's genes into the expression host to produce the lipase in soluble fraction as a bioactive form. The refolding of expressed lipase from IBs (inactive) is another practical strategy which is usually carried out through chemical and physical methods. Based on recent investigations, the current review simultaneously highlights strategies to express the bioactive lipases and recover the bioactive lipases from the IBs in insoluble form.

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.

Recent advances and challenges in the utilization of nanomaterials in transesterification for biodiesel production

Due to diminishing fossil fuel supplies and rising energy needs, there has been an ever-increasing demand for renewable energy sources. The available renewable energy resources, such as solar, wind, hydropower, and biofuels, provide a new way of supplying the world's energy needs. Biofuels stand out among them because they are sustainable and have the potential to bring the idea of a global bioeconomy to life. As a result of their production of biofuels like biomethane, biohydrogen, and biodiesel, atmospheric CO₂ is being fixed, eventually lowering the world's carbon footprint. Current developments in the production of bioenergy have concentrated on producing biodiesel among other biofuels. Biodiesel is being produced from a variety of feedstocks using a number of processes, including transesterification, micro-emulsion, direct mixing, and pyrolysis. The most popular method among these is transesterification, which makes use of a variety of catalysts. As a result of the development of nanotechnology, nanocatalysts with desirable properties, such as increased catalytic activity, increased surface area, and superior thermal stability, have been made and modified. In this review, various nanocatalyst types and manufacturing processes are examined in relation to transesterification. It explores how crucial nanocatalysts are in boosting biodiesel production, highlights potential barriers, and makes recommendations for their widespread use in the future.

Solvent tolerant enzymes in extremophiles: Adaptations and applications

Non-aqueous enzymology has always drawn attention due to the wide range of unique possibilities in biocatalysis. In general, the enzymes do not or insignificantly catalyze substrate in the presence of solvents. This is due to the interfering interactions of the solvents between enzyme and water molecules at the interface. Therefore, information about solvent-stable enzymes is scarce. Yet, solvent-stable enzymes prove quite valuable in the present day biotechnology. The enzymatic hydrolysis of the substrates in solvents synthesizes commercially valuable products, such as peptides, esters, and other transesterification products. Extremophiles, the most valuable yet not extensively explored candidates, can be an excellent source to investigate this avenue. Due to inherent structural attributes, many extremozymes can catalyze and maintain stability in organic solvents. In the present review, we aim to consolidate information about the solvent-stable enzymes from various extremophilic microorganisms. Further, it would be interesting to learn about the mechanism adapted by these microorganisms to sustain solvent stress. Various approaches to protein engineering are used to enhance catalytic flexibility and stability and broaden biocatalysis's prospects under non-aqueous conditions. It also describes strategies to achieve optimal immobilization with minimum inhibition of the catalysis. The proposed review would significantly aid our understanding of non-aqueous enzymology.

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.

A multi-component reaction for covalent immobilization of lipases on amine-functionalized magnetic nanoparticles: production of biodiesel from waste cooking oil

A new approach was used for the immobilization of Thermomyces lanuginosus lipase (TLL), Candida antarctica lipase B (CALB), and Rhizomucor miehei lipase (RML) on amine-functionalized magnetic nanoparticles (Fe3O4@SiO2-NH2) via a multi-component reaction route (using cyclohexyl isocyanide). The used method offered a single-step and very fast process for covalent attachment of the lipases under extremely mild reaction conditions (25 °C, water, and pH 7.0). Rapid and simple immobilization of 20 mg of RML, TLL, and CALB on 1 g of the support produced 100%, 98.5%, and 99.2% immobilization yields, respectively, after 2 h of incubation. The immobilized derivatives were then used for biodiesel production from waste cooking oil. Response surface methodology (RSM) in combination with central composite rotatable design (CCRD) was employed to evaluate and optimize the biodiesel production. The effect of some parameters such as catalyst amount, reaction temperature, methanol concentration, water content for TLL or water-adsorbent for RML and CALB, and ratio of t-butanol (wt%) were investigated on the fatty acid methyl esters (FAME) yield.

Production of 4-Ethyl Malate through Position-Specific Hydrolysis of Photobacterium lipolyticum M37 Lipase

Microbial lipases are used widely in the synthesis of various compounds due to their substrate specificity and position specificity. 4-Ethyl malate (4-EM) made from diethyl malate (DEM) is an important starting material used to make argon fluoride (ArF) photoresist. We tested several microbial lipases and found that Photobacterium lipolyticum M37 lipase position-specifically hydrolyzed DEM to produce 4-EM. We purified the reaction product through silica gel chromatography and confirmed that it was 4-EM through nuclear magnetic resonance analysis. To mass-produce 4-EM, DEM hydrolysis reaction was performed using an enzyme reactor system that could automatically control the temperature and pH. Effects of temperature and pH on the reaction process were investigated. As a result, 50°C and pH 4.0 were confirmed as optimal reaction conditions, meaning that M37 was specifically an acid lipase. When the substrate concentration was increased to 6% corresponding to 0.32 M, the reaction yield reached almost 100%. When the substrate concentration was further increased to 12%, the reaction yield was 81%. This enzyme reactor system and position-specific M37 lipase can be used to mass-produce 4-EM, which is required to synthesize ArF photoresist.

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.

Statistical optimization of lipase production from oil mill effluent by Acinetobacter sp. KSPE71

The present study investigated the valorization of oil-rich residues of coconut oil mill effluent (COME) as a potential growth medium for the microbial production of extracellular lipase. The bacterial species isolated from oil mill effluent, Acinetobacter sp. KSPE71 was tested for its efficiency to grow and produce lipase in undiluted COME and 0.2 % yeast extract and 0.2 % NH4Cl sup-plemented COME. In this connection, the process parameters such as pH, temperature, agitation speed, and inoculum size were optimized to maximize the production using a central composite design in the Response surface methodology. At the optimized state of pH 7.5, 35 ?C, 150 rpm with 0.6 % inoculum size, a maximum of 3.95 U mL-1 activity was obtained, four-fold higher than the basal condition. At this stage, 73 % of the lipid content was degraded. The present work results imply that the oil mill effluent can be used as a cheaper production medium for lipase and the new isolate Acinetobacter sp. KSPE71 as a potential lipase producer. The degradation of oil waste along with the production of the valuable product has multiple advantages of cost reduction of lipase and environmental concern.

Biological Methods in Biodiesel Production and Their Environmental Impact

This publication presents the technologies of enzymatic biodiesel production in comparison to the conventional methods using acid and base catalysts. Transesterification with conventional catalysts has some disadvantages, and for this reason, alternative methods of biodiesel production have been investigated. These solutions include the replacement of chemical catalysts with biological ones, which show substrate specificity in relation to fats. Replacing chemical with biological catalysts causes elimination of some disadvantages of chemical processes, for instance: high temperatures of reaction, problematic process of glycerol purification, higher alcohol-to-oil molar ratios, and soap formation. Moreover, it causes operational cost reduction and has a positive environmental impact. This is due to the lower temperature of the process, which in turn translates into lower cost of equipment and lower GHG emissions associated with the need to provide less heat to the process. The increase of biofuels’ demand has led to the technology of enzymatic biodiesel production being constantly being developed. This research mainly focuses on the possibility of obtaining cheaper and more effective biocatalysts, as well as increasing the durability of enzyme immobilization on different materials.

Optimising nutrients in the culture medium of Rhodosporidium toruloides enhances lipids production

Rhodosporidium toruloides is a useful oleaginous yeast, but lipids production is affected by various factors including nutrients in the culture medium. Herein, the R-ZL2 high-yield mutant strain was used to investigate the effects of different carbon sources (sucrose, glucose, xylose), nitrogen sources (ammonium sulphate, ammonium nitrate), and C/N ratio on lipids production capacity, get the following conclusion (1) Compared with glucose and xylose, sucrose was a superior carbon source for lipids production; (2) When using ammonium sulphate as the nitrogen source, a C/N ratio of 200:1 achieved the highest biomass, lipids production and lipids content (10.7 g/L, 6.32 g/L and 59%, respectively), and lipids produced under different C/N conditions have potential for biodiesel production (except for C/N = 40 and C/N = 80); (3) When using ammonium nitrate as the nitrogen source, a C/N ratio of 200:1 achieved the highest biomass, lipids production and lipids content (12.1 g/L, 8.25 g/L and 65%, respectively), and lipids produced under different C/N ratio conditions have potential for biodiesel production. Thus, a combination of sucrose and ammonium nitrate was optimal for the lipid accumulation in R-ZL2. The findings will lay a foundation for further improving lipids yields.

An encapsulated report on enzyme-assisted transesterification with an allusion to lipase

Biodiesel is a renewable, sulfur-free, toxic-free, and low carbon fuel which possesses enhanced lubricity. Transesterification is the easiest method employed for the production of biodiesel, in which the oil is transformed into biodiesel. Biocatalyst-mediated transesterification is more advantageous than chemical process because of its non-toxic nature, the requirement of mild reaction conditions, absence of saponification, easy product recovery, and production of high-quality biodiesel. Lipases are found to be the primary enzymes in enzyme-mediated transesterification process. Currently, researchers are using lipases as biocatalyst for transesterification. Lipases are extracted from various sources such as plants, microbes, and animals. Biocatalyst-based biodiesel production is not yet commercialized due to high-cost of purified enzymes and higher reaction time for the production process. However, research works are growing in the area of various cost-effective techniques for immobilizing lipase to improve its reusability. And further reduction in the production cost of lipases can be achieved by genetic engineering techniques. The reduction in reaction time can be achieved through ultrasonic-assisted biocatalytic transesterification. Biodiesel production by enzymatic transesterification is affected by many factors. Various methods have been developed to control these factors and improve biodiesel production. This report summarizes the various sources of lipase, various production strategies for lipase and the lipase-mediated transesterification. It is fully focused on the lipase enzyme and its role in biodiesel production. It also covers the detailed explanation of various influencing factors, which affect the lipase-mediated transesterification along with the limitations and scope of lipase in biodiesel production.

Nanomaterial conjugated lignocellulosic waste: cost-effective production of sustainable bioenergy using enzymes

The demand for novel and renewable sources of energy has increased as a result of rapid population growth, limited sources of bioenergy, and environmental pollution, caused by excessive use of fossil fuels. The need to meet future energy demands have motivated researchers to search for alternative and sustainable sources of energy. The bioconversion of lignocellulosic waste (agricultural and food waste) into biofuels shows competitive promises. Lignocellulosic waste is easily accessible and has a large enzyme system that can be immobilised onto nano-matrices. Consequently, resulting in higher biofuel production and process efficiency. However, the excessive production cost of the current procedures, which involve physical, chemical, and enzymatic reactions, is limited. The use of nanomaterials has recently been shown to concentrate lignocellulosic waste, therefore, reviewing the quest for efficient production of sustainable and cost-effective development of bioenergy from lignocellulosic wastes. This review paper explores the advanced strategies of using nanobiotechnology to combine enzyme-conjugated nanosystems for the cost-effective production of sustainable bioenergy solutions. This research will help to develop an inexpensive, eco-friendly technology for biofuels production and also help overcome the environmental burden of lignocellulosic waste worldwide.

Current Status and Future Perspectives of Supports and Protocols for Enzyme Immobilization

The market for industrial enzymes has witnessed constant growth, which is currently around 7% a year, projected to reach $10.5 billion in 2024. Lipases are hydrolase enzymes naturally responsible for triglyceride hydrolysis. They are the most expansively used industrial biocatalysts, with wide application in a broad range of industries. However, these biocatalytic processes are usually limited by the low stability of the enzyme, the half-life time, and the processes required to solve these problems are complex and lack application feasibility at the industrial scale. Emerging technologies create new materials for enzyme carriers and sophisticate the well-known immobilization principles to produce more robust, eco-friendlier, and cheaper biocatalysts. Therefore, this review discusses the trending studies and industrial applications of the materials and protocols for lipase immobilization, analyzing their advantages and disadvantages. Finally, it summarizes the current challenges and potential alternatives for lipases at the industrial level.

Trends in Widely Used Catalysts for Fatty Acid Methyl Esters (FAME) Production: A Review

The effective transesterification process to produce fatty acid methyl esters (FAME) requires the use of low-cost, less corrosive, environmentally friendly and effective catalysts. Currently, worldwide biodiesel production revolves around the use of alkaline and acidic catalysts employed in heterogeneous and homogeneous phases. Homogeneous catalysts (soluble catalysts) for FAME production have been widespread for a while, but solid catalysts (heterogeneous catalysts) are a newer development for FAME production. The rate of reaction is much increased when homogeneous basic catalysts are used, but the main drawback is the cost of the process which arises due to the separation of catalysts from the reaction media after product formation. A promising field for catalytic biodiesel production is the use of heteropoly acids (HPAs) and polyoxometalate compounds. The flexibility of their structures and super acidic properties can be enhanced by incorporation of polyoxometalate anions into the complex proton acids. This pseudo liquid phase makes it possible for nearly all mobile protons to take part in the catalysis process. Carbonaceous materials which are obtained after sulfonation show promising catalytic activity towards the transesterification process. Another promising heterogeneous acid catalyst used for FAME production is vanadium phosphate. Furthermore, biocatalysts are receiving attention for large-scale FAME production in which lipase is the most common one used successfully This review critically describes the most important homogeneous and heterogeneous catalysts used in the current FAME production, with future directions for their use.

Enhanced activity of Rhizomucor miehei lipase by directed saturation mutation of the propeptide

The propeptide is a short sequence that facilitates protein folding. In this study, four highly active Rhizomucor miehei lipase (RML) mutants were obtained through saturation mutagenesis at three propeptide positions: Ser8, Pro35, and Pro47. The enzyme activities of mutants P35 N, P47 G, P47 N, and S8E/P35S/P47A observed at 40 °C, and pH 8.0 were 10.19, 7.53, 6.15, and 8.24 times of that wild-type RML, respectively. The S8E/P35S/P47A mutant showed good thermostability. After incubation at 40 °C for 1 h, 98.98 % of its initial activity remained, whereas wild-type RML retained only 78.76 %. This result indicated that the enhancement of hydrophilicity of 35- and 47- amino-acid residues could promote the interaction between the propeptide and the mature peptide and the enzyme activity and expression level. Highly conserved sites had a more significant impact on enzyme performance than did other sites, similar to the Pro35 and Pro47 mutants showed in this study. This study provides a new idea for protein modification: enzyme performance can be improved through propeptide regulation.

Statistical Optimization of Biodiesel Production from Salmon Oil via Enzymatic Transesterification: Investigation of the Effects of Various Operational Parameters

The enzymatic transesterification of Atlantic salmon (Salmo salar) oil was carried out using Novozym 435 (immobilized lipase from Candida antartica) to produce biodiesel. A response surface modelling design was performed to investigate the relationship between biodiesel yield and several critical factors, including enzyme concentration (5, 10, or 15%), temperature (40, 45, or 50 °C), oil/alcohol molar ratio (1:3, 1:4, or 1:5) and time (8, 16, or 24 h). The results indicated that the effects of all the factors were statistically significant at p-values of 0.000 for biodiesel production. The optimum parameters for biodiesel production were determined as 10% enzyme concentration, 45 °C, 16 h, and 1:4 oil/alcohol molar ratio, leading to a biodiesel yield of 87.23%. The step-wise addition of methanol during the enzymatic transesterification further increased the biodiesel yield to 94.5%. This is the first study that focused on Atlantic salmon oil-derived biodiesel production, which creates a paradigm for valorization of Atlantic salmon by-products that would also reduce the consumption and demand of plant oils derived from crops and vegetables.

Progress in Enzymatic Biodiesel Production and Commercialization

Enzymatic biodiesel production has attracted tremendous interest due to its well-recognized advantages. However, high enzyme costs limit the application of enzymatic processes in industrial production. In the past decade, great improvements have been achieved in the lab and the industrial scale, and the production cost of the enzymatic process has been reduced significantly, which has led to it being economically competitive compared to the chemical process. This paper summarizes the progress achieved in enzymatic biodiesel research and commercialization, including reducing enzyme cost, expanding low-quality raw materials, and novel reactor designs. The advantages and disadvantages of different enzymatic processes are also compared.

A phenylalanine dynamic switch controls the interfacial activation of Rhizopus chinensis lipase

The catalytic mechanism of most lipases involves a step called "interfacial activation" which significantly increases lipases activity beyond the critical micellar concentration (CMC) of substrate. In the present study, Rhizopus chinensis lipase (RCL) was used as a research model to explore the mechanism of lipase interfacial activation beyond the CMC. Molecular dynamic (MD) simulations indicated the open- and closed-lid transitions and revealed that Phe113 was the critical site for RCL activation by its dynamic flipping. Such putative switch affecting interfacial activation has not been reported in lipase so far. The function of Phe113 was subsequently verified by mutation experiments. The F113W mutant increases the lipase catalytic efficiency (1.9 s^-1·μM^-1) to 280% at the optimum temperature (40 °C) and pH 8.5 with the addition of 0.12 μg protein in the 200 μL reaction system. MD simulations indicated that the fast flipping rate from the closed to the open state, the high open state proportion, and the exposure of the catalytic triad are the main reasons for the lipase activation. The mutual corroboration of simulations and site-directed mutagenesis results revealed the vital role of Phe113 in the lipase activation.

Halophilic archaea and their potential to generate renewable fuels and chemicals

Lignocellulosic biofuels and chemicals have great potential to reduce our dependence on fossil fuels and mitigate air pollution by cutting down on greenhouse gas emissions. Chemical, thermal, and enzymatic processes are used to release the sugars from the lignocellulosic biomass for conversion to biofuels. These processes often operate at extreme pH conditions, high salt concentrations, and/or high temperature. These harsh treatments add to the cost of the biofuels, as most known biocatalysts do not operate under these conditions. To increase the economic feasibility of biofuel production, microorganisms that thrive in extreme conditions are considered as ideal resources to generate biofuels and value-added products. Halophilic archaea (haloarchaea) are isolated from hypersaline ecosystems with high salt concentrations approaching saturation (1.5-5 M salt concentration) including environments with extremes in pH and/or temperature. The unique traits of haloarchaea and their enzymes that enable them to sustain catalytic activity in these environments make them attractive resources for use in bioconversion processes that must occur across a wide range of industrial conditions. Biocatalysts (enzymes) derived from haloarchaea occupy a unique niche in organic solvent, salt-based, and detergent industries. This review focuses on the use of haloarchaea and their enzymes to develop and improve biofuel production. The review also highlights how haloarchaea produce value-added products, such as antibiotics, carotenoids, and bioplastic precursors, and can do so using feedstocks considered "too salty" for most microbial processes including wastes from the olive-mill, shell fish, and biodiesel industries.

The Model System Saccharomyces cerevisiae Versus Emerging Non-Model Yeasts for the Production of Biofuels

Microorganisms are effective platforms for the production of a variety of chemicals including biofuels, commodity chemicals, polymers and other natural products. However, deep cellular understanding is required for improvement of current biofuel cell factories to truly transform the Bioeconomy. Modifications in microbial metabolic pathways and increased resistance to various types of stress caused by the production of these chemicals are crucial in the generation of robust and efficient production hosts. Recent advances in systems and synthetic biology provide new tools for metabolic engineering to design strategies and construct optimal biocatalysts for the sustainable production of desired chemicals, especially in the case of ethanol and fatty acid production. Yeast is an efficient producer of bioethanol and most of the available synthetic biology tools have been developed for the industrial yeast Saccharomyces cerevisiae. Non-conventional yeast systems have several advantageous characteristics that are not easily engineered such as ethanol tolerance, low pH tolerance, thermotolerance, inhibitor tolerance, genetic diversity and so forth. Currently, synthetic biology is still in its initial steps for studies in non-conventional yeasts such as Yarrowia lipolytica, Kluyveromyces marxianus, Issatchenkia orientalis and Pichia pastoris. Therefore, the development and application of advanced synthetic engineering tools must also focus on these underexploited, non-conventional yeast species. Herein, we review the basic synthetic biology tools that can be applied to the standard S. cerevisiae model strain, as well as those that have been developed for non-conventional yeasts. In addition, we will discuss the recent advances employed to develop non-conventional yeast strains that are efficient for the production of a variety of chemicals through the use of metabolic engineering and synthetic biology.

One Pot Use of Combilipases for Full Modification of Oils and Fats: Multifunctional and Heterogeneous Substrates

Lipases are among the most utilized enzymes in biocatalysis. In many instances, the main reason for their use is their high specificity or selectivity. However, when full modification of a multifunctional and heterogeneous substrate is pursued, enzyme selectivity and specificity become a problem. This is the case of hydrolysis of oils and fats to produce free fatty acids or their alcoholysis to produce biodiesel, which can be considered cascade reactions. In these cases, to the original heterogeneity of the substrate, the presence of intermediate products, such as diglycerides or monoglycerides, can be an additional drawback. Using these heterogeneous substrates, enzyme specificity can promote that some substrates (initial substrates or intermediate products) may not be recognized as such (in the worst case scenario they may be acting as inhibitors) by the enzyme, causing yields and reaction rates to drop. To solve this situation, a mixture of lipases with different specificity, selectivity and differently affected by the reaction conditions can offer much better results than the use of a single lipase exhibiting a very high initial activity or even the best global reaction course. This mixture of lipases from different sources has been called “combilipases” and is becoming increasingly popular. They include the use of liquid lipase formulations or immobilized lipases. In some instances, the lipases have been coimmobilized. Some discussion is offered regarding the problems that this coimmobilization may give rise to, and some strategies to solve some of these problems are proposed. The use of combilipases in the future may be extended to other processes and enzymes.

Concentration of Lipase from Aspergillus oryzae Expressing Fusarium heterosporum by Nanofiltration to Enhance Transesterification

Nanofiltration membrane separation is an energy-saving technology that was used in this study to concentrate extracellular lipase and increase its total activity for biodiesel production. Lipase was produced by recombinant Aspergillus oryzae expressing Fusarium heterosporum lipase (FHL). A sulfonated polyethersulfone nanofiltration membrane, NTR-7410, with a molecular weight cut-off of 3 kDa was used for the separation, because recombinant lipase has a molecular weight of approximately 20 kDa, which differs from commercial lipase at around 30 kDa for CalleraTM Trans L (CalT). After concentration via nanofiltration, recombinant lipase achieved a 96.8% yield of fatty acid methyl ester (FAME) from unrefined palm oil, compared to 50.2% for CalT in 24 h. Meanwhile, the initial lipase activity (32.6 U/mL) of recombinant lipase was similar to that of CalT. The composition of FAME produced from recombinant concentrated lipase, i.e., C14:1, C16:0, C18:0, C18:1 cis, and C18:2 cis were 0.79%, 34.46%, 5.41%, 45.90%, and 12.46%, respectively, after transesterification. This FAME composition, even after being subjected to nanofiltration, was not significantly different from that produced from CalT. This study reveals the applicability of a simple and scalable nanofiltration membrane technology that can enhance enzymatic biodiesel production.

Chemo- and biocatalytic esterification of marchantin A and cytotoxic activity of ester derivatives

Chemical and biocatalytic synthesis of seven previously undescribed marchantin A ester derivatives has been presented. Chemical synthesis afforded three peresterified bisbibenzyl products (TE1-TE3), while enzymatic method, using lipase, produced regioselective monoester derivatives (ME1-ME4). The antiproliferative activities of all prepared derivatives of marchantin A were tested on MRC-5 healthy human lung fibroblast, A549 human lung cancer, and MDA-MB-231 human breast cancer cell lines. All tested esters were less cytotoxic in comparison to marchantin A, but they also exhibited lower cytotoxicity against healthy cells. Monoesters displayed higher cytotoxic activities than the corresponding peresterified products, presumably due to the presence of free catechol group. Monohexanoyl ester ME3 displayed the same IC₅₀ like marchantin A against MDA-MB-231 cells, but the selectivity was higher. In this way, regioselective enzymatic monoesterification enhanced selectivity of marchantin A. ME3 was also the most active among all derivatives against lung cancer cells A549 with the slightly lower activity and selectivity in comparison to marchantin A.

Advances in Nanocatalysts Mediated Biodiesel Production: A Critical Appraisal

The excessive consumption of petroleum resources leads to global warming, fast depletion of petroleum reserves, as well as price instability of gasoline. Thus, there is a strong need for alternative renewable fuels to replace petroleum-derived fuels. The striking features of an alternative fuel include the low carbon footprints, renewability and affordability at manageable prices. Biodiesel, made from waste oils, animal fats, vegetal oils, is a totally renewable and non-toxic liquid fuel which has gained significant attraction in the world. Due to technological advancements in catalytic chemistry, biodiesel can be produced from a variety of feedstock employing a variety of catalysts and recovery technologies. Recently, several ground-breaking advancements have been made in nano-catalyst technology which showed the symmetrical correlation with cost competitive biodiesel production. Nanocatalysts have unique properties such as their selective reactivity, high activation energy and controlled rate of reaction, easy recovery and recyclability. Here, we present an overview of various feedstock used for biodiesel production, their composition and characteristics. The major focus of this review is to appraise the characterization of nanocatalysts, their effect on biodiesel production and methodologies of biodiesel production.

Comparison of Chemical and Enzymatic Methods for the Transesterification of Waste Fish Oil Fatty Ethyl Esters with Different Alcohols

Fatty acid esters of 2-ethyl-1-hexanol (EH), 2-hexyl-1-decanol (HD), and isopropanol have been obtained from a mixture of ethyl esters obtained as a fish oil byproduct. Homogeneous base catalysis with alkaline hydroxides and alkoxides has been compared with the use of two commercially available immobilized lipases. The enzymatic methodology is more efficient in the case of the largest alcohol (HD) mainly because of the high stability of the immobilized enzymes upon recovery and reuse. In contrast, the use of a base as a catalyst is highly favorable in the case of isopropanol because of the rather poor activity of the lipases and the low price of the bases. With EH, the activity of lipases is good but the recoverability is not as efficient; hence, basic catalysts are again the most attractive alternative. The mixtures of esters obtained may be useful as hydraulic liquids given their viscosity values.

Surfactant Imprinting Hyperactivated Immobilized Lipase as Efficient Biocatalyst for Biodiesel Production from Waste Cooking Oil

Enzymatic production of biodiesel from waste cooking oil (WCO) could contribute to resolving the problems of energy demand and environment pollutions.In the present work, Burkholderia cepacia lipase (BCL) was activated by surfactant imprinting, and subsequently immobilized in magnetic cross-linked enzyme aggregates (mCLEAs) with hydroxyapatite coated magnetic nanoparticles (HAP-coated MNPs). The maximum hyperactivation of BCL mCLEAs was observed in the pretreatment of BCL with 0.1 mM Triton X-100. The optimized Triton-activated BCL mCLEAs was used as a highly active and robust biocatalyst for biodiesel production from WCO, exhibiting significant increase in biodiesel yield and tolerance to methanol. The results indicated that surfactant imprinting integrating mCLEAs could fix BCL in their active (open) form, experiencing a boost in activity and allowing biodiesel production performed in solvent without further addition of water. A maximal biodiesel yield of 98% was achieved under optimized conditions with molar ratio of methanol-to-WCO 7:1 in one-time addition in hexane at 40 °C. Therefore, the present study displays a versatile method for lipase immobilization and shows great practical latency in renewable biodiesel production.

Structural Basis by Which the N-Terminal Polypeptide Segment of Rhizopus chinensis Lipase Regulates Its Substrate Binding Affinity

Members of an important group of industrial enzymes, Rhizopus lipases, exhibit valuable hydrolytic features that underlie their biological functions. Particularly important is their N-terminal polypeptide segment (NTPS), which is required for secretion and proper folding but is removed in the process of enzyme maturation. A second common feature of this class of lipases is the α-helical "lid", which regulates the accessibility of the substrate to the enzyme active site. Some Rhizopus lipases also exhibit "interfacial activation" by micelle and/or aggregate surfaces. While it has long been recognized that the NTPS is critical for function, its dynamic features have frustrated efforts to characterize its structure by X-ray crystallography. Here, we combine nuclear magnetic resonance spectroscopy and X-ray crystallography to determine the structure and dynamics of Rhizopus chinensis lipase (RCL) with its 27-residue NTPS prosequence (r27RCL). Both r27RCL and the truncated mature form of RCL (mRCL) exhibit biphasic interfacial activation kinetics with p-nitrophenyl butyrate (pNPB). r27RCL exhibits a substrate binding affinity significantly lower than that of mRCL due to stabilization of the closed lid conformation by the NTPS. In contrast to previous predictions, the NTPS does not enhance lipase activity by increasing surface hydrophobicity but rather inhibits activity by forming conserved interactions with both the closed lid and the core protein structure. Single-site mutations and kinetic studies were used to confirm that the NTPS serves as internal competitive inhibitor and to develop a model of the associated process of interfacial activation. These structure-function studies provide the basis for engineering RCL lipases with enhanced catalytic activities.

Halophiles and Their Vast Potential in Biofuel Production

Global warming and the limitations of using fossil fuels are a main concern of all societies, and thus, the development of alternative fuel sources is crucial to improving the current global energy situation. Biofuels are known as the best alternatives of unrenewable fuels and justify increasing extensive research to develop new and less expensive methods for their production. The most frequent biofuels are bioethanol, biobutanol, biodiesel, and biogas. The production of these biofuels is the result of microbial activity on organic substrates like sugars, starch, oil crops, non-food biomasses, and agricultural and animal wastes. Several industrial production processes are carried out in the presence of high concentrations of NaCl and therefore, researchers have focused on halophiles for biofuel production. In this review, we focus on the role of halophilic microorganisms and their current utilization in the production of all types of biofuels. Also, the outstanding potential of them and their hydrolytic enzymes in the hydrolysis of different kind of biomasses and the production of biofuels are discussed.