Lipases: An overview of its current challenges and prospectives in the revolution of biocatalysis

Biocatalyzed Synthesis of Benzoyl and Cinnamoylamides Inspired by Rice Phytoalexins

Worldwide, phytopathogenic fungi, bacteria, and viruses are responsible for huge crop losses each year, threatening agricultural progress and food security and causing massive economic damages. Pyricularia oryzae represents one of the most dangerous fungal phytopathogens being the cause of rice blast, a highly destructive disease widely distributed across the world. In this critical context, good agricultural practices necessarily need to be supported using novel, effective, and sustainable agrochemicals. It is known that plants naturally counteract exogenous infections by synthesizing defense secondary metabolites, known as phytoalexins. Inspired by N-benzoyltryptamine and N-cinnamoyltryptamine, two phytoalexins found in Oryza sativa, we designed a collection of tryptamine-based derivatives. The compounds were synthesized exploiting an enzymatic approach, using Candida antarctica Lipase B (CaL-B) as a biocatalyst and tert-amyl alcohol (t-AA) as an unconventional green solvent. The activity was evaluated against a panel of different phytopathogenic fungi as well as selected Gram-negative and Gram-positive bacteria. The obtained results pave the way for novel nature-inspired products as a valuable alternative to currently available pesticides.

Plants lipases: challenges, recent advances, and future prospects - a review

Plant lipases offer a sustainable and promising alternative for various industrial applications, with increasing use in biocatalytic processes in recent years. Leveraging plants as renewable resources reduces dependence on animal or microbial sources, providing significant potential for sustainable lipase production. These lipases are biodegradable and less toxic, enhancing their cost-effectiveness, particularly when sourced from plants with additional economic value. The diversity of plant species offers a wide array of lipases with different properties, broadening their industrial applications. Additionally, integrating plant lipase production into existing agricultural processes by using agricultural residues or by-products as enzyme sources can reduce costs and add value to waste materials. Despite their potential, several challenges must be addressed for the effective utilization of plant-derived lipases. Reducing extraction and purification costs is essential to make these enzymes competitive with other sources. Advancements in the biochemical and structural characterization of plant lipases have facilitated enzymatic engineering approaches to enhance enzyme stability, specificity, and catalytic efficiency. A review of the current research can help identify gaps and suggest new directions for enzyme development and technological advancements. Understanding the mechanisms of action and unique properties of plant lipases can drive innovations in biocatalytic processes. This review aims to highlight the characteristics of plant lipases and the challenges in their extraction, purification, and stability. This study conducted a narrative review using a database of relevant studies, selecting 92 studies. The future of plant lipases holds great promise for transformative impacts across various industries, promoting more sustainable and innovative practices.

Comparative Study of Enzymatic Lipolysis Using Nanofructosome-Coated CalB Lipase Encapsulated in Silica and Immobilized on Silica-Coated Magnetic Nanoparticles

This study evaluates the enzymatic lipolysis performance of nanofructosome-coated CalB lipase (CalB@NF) encapsulated in silica and immobilized on silica-coated magnetic nanoparticles (Si-MNP) for converting natural olive oil to oleic acid. The nanofructosome coating, composed of levan, a nanosized fructan polymer, was applied to enhance the heat and acid resistance of the CalB enzyme. To further improve functionality, CalB@NF was encapsulated in silica (CalB@NF@SiO2) or immobilized on Si-MNP using a chloropropylsilane linker. The silica-encapsulated CalB@NF (CalB@NF@SiO2) was synthesized via a sol-gel process, resulting in an average particle size of 304 nm, while the immobilized CalB@NF on Si-MNP exhibited a smaller average particle size of 58 nm. Quantitative determination of CalB in both formulations was conducted using the Bradford assay, yielding concentrations of 19.5 μg/mL for CalB@NF@SiO2 and 44.9 μg/mL for CalB@NF@Si-MNP. Enzymatic lipolysis was evaluated by measuring the production of oleic acid from natural olive oil. CalB@NF@Si-MNP achieved complete lipolysis within 3 h, whereas CalB@NF@SiO2 required 24 h to reach the same result. The lipolysis rates were 0.92 mmol/h for CalB@NF@Si-MNP and 0.21 mmol/h for CalB@NF@SiO2, indicating that CalB@NF@Si-MNP was 4.5 times faster. Regarding reusability, CalB@NF@SiO2 retained 20% more activity compared to CalB@NF@Si-MNP. While the reusability of CalB@NF@Si-MNP decreased to 76% after the first cycle, CalB@NF@SiO2 maintained nearly 100% reusability across multiple cycles. These results highlight the complementary strengths of the two formulations: CalB@NF@SiO2 offers controlled lipolysis rates, high stability, and excellent reusability, whereas CalB@NF@Si-MNP excels in rapid lipolysis. Both silica encapsulation and silica-coated magnetic nanoparticles demonstrate substantial potential for optimizing enzyme activity, stability, and reusability in diverse applications.

Enhanced activity and self-regeneration in dynameric cross-linked enzyme nanoaggregates

Directed evolution, enzyme design, and effective immobilization have been used to improve the catalytic activity. Dynamic polymers offer a promising platform to improve enzyme activity in aqueous solutions. Here, amphiphilic dynamers and lipase self-assemble into nanoparticles of 150- to 600-nanometer diameter, showing remarkable threefold enhancement in catalytic activity. In addition, they also demonstrated the ability to promote the reversible refolding of the partially or completely denatured lipase. The catalytic efficiency is completed with its more convenient handling of dynameric nanoparticles facilitating the efficient recovery and reuse of the enzyme with cost-effective uses. Molecular simulation studies revealed an in-depth understanding of how the dynamer action mechanism affects the conformational changes of lipase. The dynamer served as an effective hydrophobic support, facilitating the lid opening and substrate access to the catalytic triad, resulting in a substantial activation with an improved stability and recyclability of the lipase.

Recent insight into the advances and prospects of microbial lipases and their potential applications in industry

Enzymes play a crucial role in various industrial sectors. These biocatalysts not only ensure sustainability and safety but also enhance process efficiency through their unique specificity. Lipases possess versatility as biocatalysts and find utilization in diverse bioconversion reactions. Presently, microbial lipases are gaining significant focus owing to the rapid progress in enzyme technology and their widespread implementation in multiple industrial procedures. This updated review presents new knowledge about various origins of microbial lipases, such as fungi, bacteria, and yeast. It highlights both the traditional and modern purification methods, including precipitation and chromatographic separation, the immunopurification technique, the reversed micellar system, the aqueous two-phase system (ATPS), and aqueous two-phase flotation (ATPF), moreover, delves into the diverse applications of microbial lipases across several industries, such as food, vitamin esters, textile, detergent, biodiesel, and bioremediation. Furthermore, the present research unveils the obstacles encountered in employing lipase, the patterns observed in lipase engineering, and the application of CRISPR/Cas genome editing technology for altering the genes responsible for lipase production. Additionally, the immobilization of microorganisms' lipases onto various carriers also contributes to enhancing the effectiveness and efficiencies of lipases in terms of their catalytic activities. This is achieved by boosting their resilience to heat and ionic conditions (such as inorganic solvents, high-level pH, and temperature). The process also facilitates the ease of recycling them and enables a more concentrated deposition of the enzyme onto the supporting material. Consequently, these characteristics have demonstrated their suitability for application as biocatalysts in diverse industries.

Chemoenzymatic Dynamic Kinetic Resolution Protocol with an Immobilized Oxovanadium as a Racemization Catalyst

An excellent compatible and cost-effective dynamic kinetic resolution (DKR) protocol has been developed by combining a novel immobilized oxovanadium racemization catalyst onto cheap diatomite (V-D) with an immobilized lipase LA resolution catalyst onto a macroporous resin (LA-MR). V-D was prepared via grinding immobilization, which may become a promising alternative for the immobilization of metals, especially precious metals due to its low cost, high efficiency, easy separation, and large reaction interface. The DKR afforded high yield (96.1%), e.e. (98.67%), and Sel (98.28%) under optimal conditions established using response surface methodology as follows: the amount of V-D 10.83 mg, reaction time 51.2 h, and temperature 48.1 °C, respectively, indicating that all the reactions in the DKR were coordinated very well. The DKR protocol was also found to have high stability up to six reuses. V-D exhibited excellent compatibility with LA-MR because the lipase immobilized onto MR did not physically contact with the vanadium species immobilized onto diatomite, thus avoiding inactivation. Considering that lipase, oxovanadium, diatomite, and MR used are relatively inexpensive, and the adsorption or grinding immobilization is simple, the LA-V-MD DKR by coupling LA-MR with V-D is a cost-effective and promising protocol for chiral secondary alcohols.

Biological valorization of lignin-derived vanillin to vanillylamine by recombinant E. coli expressing ω-transaminase and alanine dehydrogenase in a petroleum ether-water system

Vanillylamine, as an important drug precursor and fine chemical intermediate, has great economic value. By constructing a strategy of double enzyme co-expression, one newly constructed recombinant E. coli HNIQLE-AlaDH expressing ω-transaminase from Aspergillus terreus and alanine dehydrogenase from Bacillus subtilis was firstly used aminate lignin-derived vanillin to vanillylamine by using a relatively low dosage of amine donors (vanillin:L-alanine:isopropylamine = 1:1:1, mol/mol/mol). In addition, in a two-phase system (water:petroleum ether = 80:20 v/v), the bioconversion of vanillin to vanillylamine was catalyzed by HNIQLE-AlaDH cell under the ambient condition, and the vanillylamine yield was 71.5%, respectively. This double-enzyme HNIQLE-AlaDH catalytic strategy was applied to catalyze the bioamination of furfural and 5-hydroxymethylfurfural with high amination efficiency. It showed that the double-enzyme catalytic strategy in this study promoted L-alanine to replace D-Alanine to participate in bioamination of vanillin and its derivatives, showing a great prospect in the green biosynthesis of biobased chemicals from biomass.

Immobilization of Lipase B from Candida antarctica in Octyl-Vinyl Sulfone Agarose: Effect of the Enzyme-Support Interactions on Enzyme Activity, Specificity, Structure and Inactivation Pathway

Lipase B from Candida antarctica was immobilized on heterofunctional support octyl agarose activated with vinyl sulfone to prevent enzyme release under drastic conditions. Covalent attachment was established, but the blocking step using hexylamine, ethylenediamine or the amino acids glycine (Gly) and aspartic acid (Asp) altered the results. The activities were lower than those observed using the octyl biocatalyst, except when using ethylenediamine as blocking reagent and p-nitrophenol butyrate (pNPB) as substrate. The enzyme stability increased using these new biocatalysts at pH 7 and 9 using all blocking agents (much more significantly at pH 9), while it decreased at pH 5 except when using Gly as blocking agent. The stress inactivation of the biocatalysts decreased the enzyme activity versus three different substrates (pNPB, S-methyl mandelate and triacetin) in a relatively similar fashion. The tryptophane (Trp) fluorescence spectra were different for the biocatalysts, suggesting different enzyme conformations. However, the fluorescence spectra changes during the inactivation were not too different except for the biocatalyst blocked with Asp, suggesting that, except for this biocatalyst, the inactivation pathways may not be so different.

Solvent-dependent activity of Candida antarctica lipase B and its correlation with a regioselective mono aza-Michael addition - experimental and molecular dynamics simulation studies

With the aim of gaining understanding of the molecular basis of commercially available Candida antarctica lipase B (CALB) immobilized on polyacrylic resin catalyzed regioselective mono aza-Michael addition of Benzhydrazide to Diethyl maleate we decided to carry out molecular dynamics (MD) simulation studies in parallel with our experimental study. We found a correlation between the activity of CALB and the choice of solvent. Our study showed that solvent affects the performance of the enzyme due to the binding of solvent molecules to the enzyme active site region, and the solvation energy of substrates in the different solvents. We also found that CALB is only active in nonpolar solvent (i.e. Hexane), and therefore we investigated the influence of Hexane on the catalytic activity of CALB for the reaction. The results of this study and related experimental validation from our studies have been discussed here.

Shortening Synthetic Routes to Small Molecule Active Pharmaceutical Ingredients Employing Biocatalytic Methods

Biocatalysis, using enzymes for organic synthesis, has emerged as powerful tool for the synthesis of active pharmaceutical ingredients (APIs). The first industrial biocatalytic processes launched in the first half of the last century exploited whole-cell microorganisms where the specific enzyme at work was not known. In the meantime, novel molecular biology methods, such as efficient gene sequencing and synthesis, triggered breakthroughs in directed evolution for the rapid development of process-stable enzymes with broad substrate scope and good selectivities tailored for specific substrates. To date, enzymes are employed to enable shorter, more efficient, and more sustainable alternative routes toward (established) small molecule APIs, and are additionally used to perform standard reactions in API synthesis more efficiently. Herein, large-scale synthetic routes containing biocatalytic key steps toward >130 APIs of approved drugs and drug candidates are compared with the corresponding chemical protocols (if available) regarding the steps, reaction conditions, and scale. The review is structured according to the functional group formed in the reaction.

Lipase-Catalyzed Epoxy-Acid Addition and Transesterification: from Model Molecule Studies to Network Build-Up

Commercially available lipase from Pseudomonas stutzeri (lipase TL) is investigated as a biocatalyst for the formation of an acid-epoxy chemical network. Molecular model reactions are performed by reacting 2-phenyl glycidyl ether and hexanoic acid in bulk, varying two parameters: temperature and water content. Characterizations of the formed products by ¹H NMR spectroscopy and gas chromatography-mass spectrometry combined with enzymatic assays confirm that lipase TL is able to simultaneously promote acid-epoxy addition and transesterification reactions below 100 °C and solely the acid-epoxy addition after denaturation at T > 100 °C. A prototype bio-based chemical network with β-hydroxyester links was obtained using resorcinol diglycidyl ether and sebacic acid as monomers with lipase TL as catalyst. Differential scanning calorimetry, attenuated total reflection, and swelling analysis confirm gelation of the network.

Power of Biocatalysis for Organic Synthesis

Biocatalysis, using defined enzymes for organic transformations, has become a common tool in organic synthesis, which is also frequently applied in industry. The generally high activity and outstanding stereo-, regio-, and chemoselectivity observed in many biotransformations are the result of a precise control of the reaction in the active site of the biocatalyst. This control is achieved by exact positioning of the reagents relative to each other in a fine-tuned 3D environment, by specific activating interactions between reagents and the protein, and by subtle movements of the catalyst. Enzyme engineering enables one to adapt the catalyst to the desired reaction and process. A well-filled biocatalytic toolbox is ready to be used for various reactions. Providing nonnatural reagents and conditions and evolving biocatalysts enables one to play with the myriad of options for creating novel transformations and thereby opening new, short pathways to desired target molecules. Combining several biocatalysts in one pot to perform several reactions concurrently increases the efficiency of biocatalysis even further.

Biocatalytic Approach for Novel Functional Oligoesters of ε-Caprolactone and Malic Acid

Biocatalysis has developed in the last decades as a major tool for green polymer synthesis. The particular ability of lipases to catalyze the synthesis of novel polymeric materials has been demonstrated for a large range of substrates. In this work, novel functional oligoesters were synthesized from ε-caprolactone and D,L/L-malic acid by a green and sustainable route, using two commercially available immobilized lipases as catalysts. The reactions were carried out at different molar ratios of the comonomers in organic solvents, but the best results were obtained in solvent-free systems. Linear and cyclic oligomeric products with average molecular weights of about 1500 Da were synthesized, and the formed oligoesters were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The oligoester synthesis was not enantioselective in the studied reaction conditions. The operational stability of both biocatalysts (Novozyme 435 and GF-CalB-IM) was excellent after reutilization in 13 batch reaction cycles. The thermal properties of the reaction products were investigated by thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis. The presence of polar pendant groups in the structure of these oligomers could widen the possible applications compared to the oligomers of ε-caprolactone or allow the conversion to other functional materials.

Comparative Studies on the Susceptibility of (R)-2,3-Dipalmitoyloxypropylphosphonocholine (DPPnC) and Its Phospholipid Analogues to the Hydrolysis or Ethanolysis Catalyzed by Selected Lipases and Phospholipases

Susceptibility of soybean phosphatidylcholine, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and its phosphono analogue (R)-2,3-dipalmitoyloxypropylphosphonocholine (DPPnC) towards selected lipases and phospholipases was compared. The ethanolysis of substrates at sn-1 position was carried out by lipase from Mucor miehei (Lipozyme®) and lipase B from Candida antarctica (Novozym 435) in 95% ethanol at 30 °C, and the hydrolysis with LecitaseTM Ultra was carried out in hexane/water at 50 °C. Hydrolysis at sn-2 position was carried out in isooctane/Tris-HCl/AOT system at 40 °C using phospholipase A2 (PLA2) from porcine pancreas and PLA2 from bovine pancreas or 25 °C using PLA2 from bee venom. Hydrolysis in the polar part of the studied compounds was carried out at 30 °C in acetate buffer/ethyl acetate system using phospholipase D (PLD) from Streptococcus sp. and PLD from white cabbage or in Tris-HCl buffer/methylene chloride system at 35 °C using PLD from Streptomyces chromofuscus. The results showed that the presence of C-P bond between glycerol and phosphoric acid residue in DPPnC increases the rate of enzymatic hydrolysis or ethanolysis of ester bonds at the sn-1 and sn-2 position and decreases the rate of hydrolysis in the polar head of the molecule. The most significant changes in the reaction rates were observed for reaction with PLD from Streptococcus sp. and PLD from Streptomyces chromofuscus that hydrolyzed DPPnC approximately two times slower than DPPC and soybean PC. The lower susceptibility of DPPnC towards enzymatic hydrolysis by phospholipases D gives hope for the possibility of using DPPnC-like phosphonolipids as the carriers of bioactive molecules that, instead of choline, can be bounded with diacylpropylphosphonic acids (DPPnA).

Breaking Molecular Symmetry through Biocatalytic Reactions to Gain Access to Valuable Chiral Synthons

In this review the recent reports of biocatalytic reactions applied to the desymmetrization of meso-compounds or symmetric prochiral molecules are summarized. The survey of literature from 2015 up to date reveals that lipases are still the most used enzymes for this goal, due to their large substrate tolerance, stability in different reaction conditions and commercial availability. However, a growing interest is focused on the use of other purified enzymes or microbial whole cells to expand the portfolio of exploitable reactions and the molecular diversity of substrates to be transformed. Biocatalyzed desymmetrization is nowadays recognized as a reliable and efficient approach for the preparation of pharmaceuticals or natural bioactive compounds and many processes have been scaled up for multigram preparative purposes, also in continuous-flow conditions.

Efficient microbial resolution of racemic methyl 3-cyclohexene-1-carboxylate as chiral precursor of Edoxaban by newly identified Acinetobacter sp. JNU9335

Optically active 3-cyclohexene-1-carboxylic acid (CHCA) derivatives are important pharmaceutical intermediates. Due to the special rotatable structure, enantioselective preparation of chiral CHCA is hard to achieve. To identify efficient and enantioselective hydrolases for the biosynthesis of CHCA from methyl 3-cyclohexene-1-carboxylate (CHCM), target-oriented screening from soil samples and gene mining from genome database were explored. All putative hydrolases attempted displayed low enantioselectivity. A hydrolase-producing strain JNU9335 was successfully identified with relatively high enantioselectivity, and was designated as a strain of Acinetobacter sp. according to 16S rDNA sequence and phylogenetic analysis. After optimization, strain JNU9335 could produce 233 U·L^‒1 hydrolase with E value of 21. Isooctane/aqueous biphasic system is favorable for the enzymatic resolution of CHCM, the E value of JNU9335 could further be increased to 36. The newly identified JNU9335 could tolerate as high as 1.0 M CHCM, producing (S)-CHCM with ee_s of 99.6% and isolation yield of 34.7%. This study provides an efficient biocatalyst for the preparation of chiral 3-cyclohexene-1-carboxylic acid derivatives.

Unexplored lipolytic activity of Escherichia coli: Implications for lipase cloning

Recent investigations on cloned bacterial lipases performed in our laboratory revealed the presence of lipolytic activity that was not due to the cloned lipase-coding gene but was probably the result of an intrinsic activity of Escherichia coli itself. To confirm such a hypothesis, we assayed the activity of frequently used E. coli strains by fast paper tests, zymograms and spectrofluorometry. A band of Ca. 18-20 kDa showing activity on MUF-butyrate was detected in zymogram analysis of crude cell extracts in all E. coli strains assayed. Moreover, the spectrofluorometric results obtained confirmed the presence of low but significant lipolytic activity in E. coli, with strain BL21 showing the highest activity. Detailed characterization of such a lipolytic activity was performed using E. coli BL21 cell extracts, where preference for C7 substrates was found, although shorter substrates were also hydrolysed to a minor extent. Interestingly, E. coli lipolytic activity displays traits of a thermophilic enzyme, showing maximum activity at 50 °C and pH 8, an unexpected feature never described before. Kinetic and inhibition analysis were also performed showing that activity can be inhibited by several metal ions or by Triton X-100® and SDS, used in zymogram analysis. Such properties ‒ low activity, preference for medium chain-length substrates, and high operational temperature ‒ might justify why this activity had gone unexplored until now, even when many lipases and esterases have been cloned and expressed in E. coli strains in the past. From now on, lipase researchers should take into consideration the presence of such a basal lipolytic activity before starting their lipase cloning or expression experiments in E.coli.

Free and Immobilized Lecitase™ Ultra as the Biocatalyst in the Kinetic Resolution of (E)-4-Arylbut-3-en-2-yl Esters

The influence of buffer type, co-solvent type, and acyl chain length was investigated for the enantioselective hydrolysis of racemic 4-arylbut-3-en-2-yl esters using Lecitase™ Ultra (LU). Immobilized preparations of the Lecitase™ Ultra enzyme had significantly higher activity and enantioselectivity than the free enzyme, particularly for 4-phenylbut-3-en-2-yl butyrate as the substrate. Moreover, the kinetic resolution with the immobilized enzyme was achieved in a much shorter time (24–48 h). Lecitase™ Ultra, immobilized on cyanogen bromide-activated agarose, was particularly effective, producing, after 24 h of reaction time in phosphate buffer (pH 7.2) with acetone as co-solvent, both (R)-alcohols and unreacted (S)-esters with good to excellent enantiomeric excesses (ee 90–99%). These conditions and enzyme were also suitable for the kinetic separation of racemic (E)-4-phenylbut-3-en-2-yl butyrate analogs containing methyl substituents on the benzene ring (4b,4c), but they did not show any enantioselectivity toward (E)-4-(4’-methoxyphenyl)but-3-en-2-yl butyrate (4d).

Enzymatic synthesis of short-chain flavor esters from natural sources using tailored magnetic biocatalysts

Immobilized lipases are excellent biocatalysts for the enzymatic synthesis of short- and medium-chain fatty esters used as food flavor compounds. Herein a new approach for a magnetic core-shell biocatalyst by immobilization of Candida antarctica B lipase is reported, coating single-core magnetic nanoparticles with an organic shell, preferably poly(benzofurane-co-arylacetic acid), followed by the covalent attachment of the enzyme and embedment of the primary biocatalyst in a silica layer. Although covalent and sol-gel immobilization were efficient on their own, their combination can ensure additional operational stability through multi-point linkages. Moreover, silanes holding glycidoxy groups, which can also form covalent linkages, have been successfully used as precursors for the silica coating layer. The structural, magnetic and morphological characteristics were assessed by TEM, SEM-EDX, X-ray photoelectron spectroscopy and vibrating sample magnetometry. The new biocatalysts demonstrated high catalytic efficiency in the solventless synthesis of isoamyl esters of natural carboxylic acids, also in multiple reaction cycles.

Bioconversion of Chicken Feather Meal by Aspergillus niger: Simultaneous Enzymes Production Using a Cost-Effective Feedstock Under Solid State Fermentation

This study reported for the first time the simultaneous production of hydrolytic enzymes by Aspergillus niger under solid state fermentation using chicken feather meal as substrate. The effect of some culture parameters for production of protease, lipase, phytase and keratinase enzymes was evaluated using a central composite rotatable design. The results obtained demonstrated that the independent variables initial moisture of the culture medium and incubation temperature presented as highly significant on the enzymes production. The production of protease and lipase followed a similar profile, in which the highest values of enzymatic activities were detected after 48 h of fermentation. The conduction of the fermentative process using an initial moisture of 50%, 30 °C as incubation temperature and supplementation of the feather meal with 15% wheat bran resulted in higher yields of protease (> 300 U g^-1) and lipase (> 90 U g^-1) after 48 h and satisfactory values of phytase activity (> 70 U g^-1) after 72 h. No significant effects of the independent variables on keratinase production were observed. However, under the selected conditions for the other enzymes, keratinase production reached values higher than 13 U g^-1 after 72 h fermentation. Thus, our work contributed to the proposal of an alternative process for the simultaneous production of proteases, lipases, phytases and keratinases in a single and simplified process using chicken feather meal.

N-terminal domain replacement changes an archaeal monoacylglycerol lipase into a triacylglycerol lipase

BACKGROUND

Lipolytic enzymes of hyperthermophilic archaea generally prefer small carbon chain fatty acid esters (C₂-C₁₂) and are categorized as esterases. However, a few have shown activity with long-chain fatty acid esters, but none of them have been classified as a true lipase except a lipolytic enzyme AFL from Archaeglobus fulgidus. Thus, our main objective is to engineer an archaeal esterase into a true thermostable lipase for industrial applications. Lipases which hydrolyze long-chain fatty acid esters display an interfacial activation mediated by the lid domain which lies over active site and switches to open conformation at the oil-water interface. Lid domains modulate enzyme activities, substrate specificities, and stabilities which have been shown by protein engineering and mutational analyses. Here, we report engineering of an uncharacterized monoacylglycerol lipase (TON-LPL) from an archaeon Thermococcus onnurineus (strain NA1) into a triacylglycerol lipase (rc-TGL) by replacing its 61 N-terminus amino acid residues with 118 residues carrying lid domain of a thermophilic fungal lipase-Thermomyces lanuginosus (TLIP).

RESULTS

TON-LPL and rc-TGL were cloned and overexpressed in E. coli, and the proteins were purified by Ni-NTA affinity chromatography for biochemical studies. Both enzymes were capable of hydrolyzing various monoglycerides and shared the same optimum pH of 7.0. However, rc-TGL showed a significant decrease of 10 °C in its optimum temperature (T_opt). The far UV-CD spectrums were consistent with a well-folded α/β-hydrolase fold for both proteins, but gel filtration chromatography revealed a change in quaternary structure from trimer (TON-LPL) to monomer (rc-TGL). Seemingly, the difference in the oligomeric state of rc-TGL may be linked to a decrease in temperature optimum. Nonetheless, rc-TGL hydrolyzed triglycerides and castor oil, while TON-LPL was not active with these substrates.

CONCLUSIONS

Here, we have confirmed the predicted esterase activity of TON-LPL and also performed the lid engineering on TON-LPL which effectively expanded its substrate specificity from monoglycerides to triglycerides. This approach provides a way to engineer other hyperthermophilic esterases into industrially suitable lipases by employing N-terminal domain replacement. The immobilized preparation of rc-TGL has shown significant activity with castor oil and has a potential application in castor oil biorefinery to obtain value-added chemicals.

Filling the Void: Introducing Aromatic Interactions into Solvent Tunnels To Enhance Lipase Stability in Methanol

An enhanced stability of enzymes in organic solvents is desirable under industrial conditions. The potential of lipases as biocatalysts is mainly limited by their denaturation in polar alcohols. In this study, we focused on selected solvent tunnels in lipase from Geobacillus stearothermophilus T6 to improve its stability in methanol during biodiesel synthesis. Using rational mutagenesis, bulky aromatic residues were incorporated to occupy solvent channels and induce aromatic interactions leading to a better inner core packing. The chemical and structural characteristics of each solvent tunnel were systematically analyzed. Selected residues were replaced with Phe, Tyr, or Trp. Overall, 16 mutants were generated and screened in 60% methanol, from which 3 variants showed an enhanced stability up to 81-fold compared with that of the wild type. All stabilizing mutations were found in the longest tunnel detected in the "closed-lid" X-ray structure. The combination of Phe substitutions in an A187F/L360F double mutant resulted in an increase in unfolding temperature (T_m ) of 7°C in methanol and a 3-fold increase in biodiesel synthesis yield from waste chicken oil. A kinetic analysis with p-nitrophenyl laurate revealed that all mutants displayed lower hydrolysis rates (k _cat), though their stability properties mostly determined the transesterification capability. Seven crystal structures of different variants were solved, disclosing new π-π or CH/π intramolecular interactions and emphasizing the significance of aromatic interactions for improved solvent stability. This rational approach could be implemented for the stabilization of other enzymes in organic solvents.IMPORTANCE Enzymatic synthesis in organic solvents holds increasing industrial opportunities in many fields; however, one major obstacle is the limited stability of biocatalysts in such a denaturing environment. Aromatic interactions play a major role in protein folding and stability, and we were inspired by this to redesign enzyme voids. The rational protein engineering of solvent tunnels of lipase from Geobacillus stearothermophilus is presented here, offering a promising approach to introduce new aromatic interactions within the enzyme core. We discovered that longer tunnels leading from the surface to the enzyme active site were more beneficial targets for mutagenesis for improving lipase stability in methanol during biodiesel biosynthesis. A structural analysis of the variants confirmed the generation of new interactions involving aromatic residues. This work provides insights into stability-driven enzyme design by targeting the solvent channel void.

Immobilization of Eversa Lipase on Octyl Agarose Beads and Preliminary Characterization of Stability and Activity Features

Eversa is an enzyme recently launched by Novozymes to be used in a free form as biocatalyst in biodiesel production. This paper shows for first time the immobilization of Eversa (a commercial lipase) on octyl and aminated agarose beads and the comparison of the enzyme properties to those of the most used lipase, the isoform B from Candida antarctica (CALB) immobilized on octyl agarose beads. Immobilization on octyl and aminated supports of Eversa has not had a significant effect on enzyme activity versus p-nitrophenyl butyrate (pNPB) under standard conditions (pH 7), but immobilization on octyl agarose beads greatly enhanced the stability of the enzyme under all studied conditions, much more than immobilization on aminated support. Octyl-Eversa was much more stable than octyl-CALB at pH 9, but it was less stable at pH 5. In the presence of 90% acetonitrile or dioxane, octyl-Eversa maintained the activity (even increased the activity) after 45 days of incubation in a similar way to octyl-CALB, but in 90% of methanol, results are much worse, and octyl-CALB became much more stable than Eversa. Coating with PEI has not a clear effect on octyl-Eversa stability, although it affected enzyme specificity and activity response to the changes in the pH. Eversa immobilized octyl supports was more active than CALB versus triacetin or pNPB, but much less active versus methyl mandelate esters. On the other hand, Eversa specificity and response to changes in the medium were greatly modulated by the immobilization protocol or by the coating of the immobilized enzyme with PEI. Thus, Eversa may be a promising biocatalyst for many processes different to the biodiesel production and its properties may be greatly improved following a suitable immobilization protocol, and in some cases is more stable and active than CALB.

High-level expression and characterization of a stereoselective lipase from Aspergillus oryzae in Pichia pastoris

Pichia pastoris expression is a mature and efficient eukaryotic expression system. In this work, Aspergillus oryzae lipase (AOL, with the molecular mass of 28 kDa), which can perform highly stereoselective hydrolysis of (R, S)-methyl 2-(4-hydroxyphenoxy) propanoate, was expressed in P. pastoris X-33. The specific activity of AOL was 432 U/mg, which was obtained by fed-batch cultivation in a 5 L bioreactor using a methanol feeding strategy. After fermentation, the supernatant was concentrated by ultrafiltration with a 10 kDa cut-off membrane and purified with DEAE-Sepharose™ FF ion-exchange chromatography and phenyl Seflnose™ 6 FF hydrophobic interaction chromatography. The purified lipase activity reached 5509 U/mg. AOL showed high activity toward short-chain triacylglyceride (C₄), and the optimum temperature and pH were 40 °C and 8.0, respectively. The purified enzyme activity was inhibited by Zn²⁺ and Cu²⁺. Moreover, the K_m and V_max values were 1 mM and 32.89 mmol/min, respectively.

Application of Lecitase® Ultra-Catalyzed Hydrolysis to the Kinetic Resolution of (E)-4-phenylbut-3-en-2-yl Esters

The possibility of using Lecitase® Ultra as a novel alternative biocatalyst for the kinetic resolution of model racemic allyl esters of (E)-4-phenylbut-3-en-3-ol: Acetate (4a) and propionate (4b) through their enantioselective hydrolysis was investigated. Reaction afforded (+)-(R)-alcohol (3) and unreacted (−)-(S)-ester (4a or 4b). Hydrolysis of propionate 4b proceeded with higher enantioselectivity than acetate 4a. (R)-Alcohol (3) with highest enantiomeric excess (93–99%) was obtained at 20–30 °C by hydrolysis of propionate 4b, while the highest optical purity of unreacted substrate was observed for (S)-acetate 4a (ee = 34–56%). The highest enantioselectivity was found for the hydrolysis of propionate 4b catalyzed at 30 °C (E = 38). Reaction carried out at 40 °C significantly lowered enantiomeric excess of produced alcohol 3 and enantioselectivity in resolution. Lecitase® Ultra catalyzed the enantioselective hydrolysis of allyl esters 4a,b according to Kazlauskas’ rule to produce (R)-alcohol 3 and can find application as a novel biocatalyst in the processes of kinetic resolution of racemic allyl esters.

Effect of Surfactant Structure on the Superactivity of Candida rugosa Lipase

In this work, we present the effects of ionic and zwitterionic surfactants on the hydrolytic activity of Candida rugosa lipase (CRL), one of the most important and widely used microbial lipases. A series of amine N-oxide surfactants was studied to explore the relationship between their molecular structures and their effect on catalytic properties of CRL. These zwitterionic amphiphiles are known for their ability to form aggregates that can increase their size, thanks to a sphere-rod transition, without any additive. Enzyme activity seemed to be improved by morphological changes of micelles from spherical to rod-like, and the structure of the monomers played a crucial role in this transition. In fact, all the amine oxides investigated provoked superactivation, but the CRL activity increased by lengthening the alkyl chain of N-oxide surfactants, whereas it decreased in the presence of bulky head groups. Superactivity was mainly because of an increase in k_cat (0.57 s^-1 in buffer, 0.80-1.99 s^-1 in surfactant solutions) and, in some cases, a decrease in K_M (2 × 10^-3 M in buffer, 1.08-4.28 × 10^-3 M in surfactant solutions). Micelles seemed to play a dual role: superactivity occurred at surfactant concentrations higher than their critical micelle concentration, but, on the other hand, micelles subtracted the substrate from the bulk, making it unavailable for the catalysis.

Scale-up of PUF-immobilized fungal chitosanase-lipase preparation production

Mucor circinelloides IBT-83 mycelium that exhibits both lipolytic (A_L) and chitosanolytic (A_CH) activities was immobilized into polyurethane foam in a 30 L laboratory fermenter. The process of immobilization was investigated in terms of the carrier porosity, its type, amount, and shape, location inside the fermenter, mixing, and aeration parameters during the culture, as well as downstream processing operations. The selected conditions allowed for immobilization of approximately 7 g of defatted and dried mycelium in 1 g of carrier, i.e., seven times more than achievable in 1 L shake-flasks. Enzymatic preparation obtained by this method exhibited both the chitosanolytic (A_CH 432.5 ± 6.8 unit/g) and lipolytic (A_L 150.0 ± 9.3 U/g) activities. The immobilized preparation was successfully used in chitosan hydrolysis to produce chitooligosaccharides and low molecular weight chitosan, as well as in waste fats degradation and in esters synthesis in nonaqueous media. It was found that the half-life of immobilized preparations stored at room temperature is on average of 200 days.

Bacillus sp. JR3 esterase LipJ: A new mesophilic enzyme showing traces of a thermophilic past

A search for extremophile enzymes from ancient volcanic soils in El Hierro Island (Canary Islands, Spain) allowed isolation of a microbial sporulated strain collection from which several enzymatic activities were tested. Isolates were obtained after sample cultivation under several conditions of nutrient contents and temperature. Among the bacterial isolates, supernatants from the strain designated JR3 displayed high esterase activity at temperatures ranging from 30 to 100°C, suggesting the presence of at least a hyper-thermophilic extracellular lipase. Sequence alignment of known thermophilic lipases allowed design of degenerated consensus primers for amplification and cloning of the corresponding lipase, named LipJ. However, the cloned enzyme displayed maximum activity at 30°C and pH 7, showing a different profile from that observed in supernatants of the parental strain. Sequence analysis of the cloned protein showed a pentapeptide motif -GHSMG- distinct from that of thermophilic lipases, and much closer to that of esterases. Nevertheless, the 3D structural model of LipJ displayed the same folding as that of thermophilic lipases, suggesting a common evolutionary origin. A phylogenetic study confirmed this possibility, positioning LipJ as a new member of the thermophilic family of bacterial lipases I.5. However, LipJ clusters in a clade close but separated from that of Geobacillus sp. thermophilic lipases. Comprehensive analysis of the cloned enzyme suggests a common origin of LipJ and other bacterial thermophilic lipases, and highlights the most probable divergent evolutionary pathway followed by LipJ, which during the harsh past times would have probably been a thermophilic enzyme, having lost these properties when the environment changed to more benign conditions.

Identification, expression and characterization of an R-ω-transaminase from Capronia semiimmersa

Chiral amines are essential precursors in the production of biologically active compounds, including several important drugs. Among the biocatalytic strategies that have been developed for their synthesis, the use of ω-transaminases (ω-TA) appears as an attractive alternative allowing the stereoselective amination of prochiral ketones. However, the problems associated with narrow substrate specificity, unfavourable reaction equilibrium and expensive amine donors still hamper its industrial application. The search for novel enzymes from nature can contribute to expand the catalytic repertoire of ω-TA and help to circumvent some of these problems. A genome mining approach, based on the work described by Höhne et al., was applied for selection of potential R-ω-TA. Additional criteria were used to select an enzyme that differs from previously described ones. A candidate R-ω-TA from Capronia semiimmersa was selected, cloned and expressed in Escherichia coli. Interestingly, alignment of this enzyme with previously reported TA sequences revealed the presence of two additional amino acid residues in a loop close to the active site. The impact of this change was analysed with a structural model based on crystallized R-ω-TAs. Analysis of the substrate specificity of R-ω-TA from C. semiimmersa indicates that it accepts a diversity of ketones as substrates yielding the corresponding amine with good yields and excellent enantioselectivity. The expressed enzyme accepts isopropylamine as amine donor what makes it suitable for industrial processes.