Natural flavor ester synthesis catalyzed by lipases

Solvent-free synthesis of hydrophobic and amphiphilic esters using a chemically modified lipase from Thermomyces lanuginosus: a comparative study with native and immobilized forms

Using lipases to catalyze the synthesis of the most differentiated type of compounds remains one of the major challenges among scientists. Seeking more economic and advantageous catalysts is a current goal of green chemistry. In this work, we demonstrate the potential of a chemically modified form of lipase from Thermomyces lanuginosus (cmLTL) for the synthesis of both hydrophobic (heptyl heptanoate, heptyl octanoate, heptyl decanoate, decyl heptanoate, decyl octanoate and decyl decanoate) and amphiphilic (2-(2-ethoxyethoxy)ethyl oleate and 2-(2-ethoxyethoxy)ethyl linoleate) esters, in bulk. The results were compared with its native (LTL) and immobilized (imLTL) forms. The data revealed that LTL showed poor activity for all reactions performed with n-heptane (η<20 %). ImLTL was able to synthesize all hydrophobic esters (η>60 %), with exception of the short ester, heptyl heptanoate. cmLTL was the only form of LTL capable of producing hydrophobic and amphiphilic esters, without compromising the yield when the reactions were performed under solvent-free conditions (>50 %). Molecular modeling showed that the active pocket of cmLTL is able to deeply internalize transcutol, with stronger interactions, justifying the outstanding results obtained. Furthermore, owing to the possibility of cmLTL filtration, the reusability of the catalyst is ensured for at least 6 cycles, without compromising the reaction yields.

Enzymatic synthesis of novel pyrrole esters and their thermal stability

In the present work a simple enzymatic approach (Novozym 435) for transesterification to synthesize pyrrole esters was reported. To generate the best reaction conditions, which resulted in the optimum yield of 92%, the effects of lipase type, solvent, lipase load, molecular sieves, substrate molar ratio of esters to alcohol, reaction temperature, reaction duration, and speed of agitation were evaluated. The range of alcohols was assessed under optimal circumstances. The spectrum observations conclusively demonstrated that the compounds could be generated with high yield under the circumstances utilized for synthesis. The odor characteristics of the pyrrolyl esters obtained were examined by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Among them, compounds of benzhydryl 1H-pyrrole-2-carboxylate (3j), butyl 1H-pyrrole-2-carboxylate (3k) and pentyl 1H-pyrrole-2-carboxylate (3l) present sweet and acid aroma. In addition, the thermal degradation process was further studied using the Py-GC/MS (pyrolysis-gas chromatography/mass spectrometry), TG (thermogravimetry), and DSC (differential scanning calorimeter) techniques. The outcomes of the Py-GC/MS, TG, and DSC techniques show that they have excellent thermal stability.

Trends in the Use of Lipases: A Systematic Review and Bibliometric Analysis

Scientific mapping using bibliometric data network analysis was applied to analyze research works related to lipases and their industrial applications, evaluating the current state of research, challenges, and opportunities in the use of these biocatalysts, based on the evaluation of a large number of publications on the topic, allowing a comprehensive systematic data analysis, which had not yet been conducted in relation to studies specifically covering lipases and their industrial applications. Thus, studies involving lipase enzymes published from 2018 to 2022 were accessed from the Web of Science database. The extracted records result in the analysis of terms of bibliographic compatibility among the articles, co-occurrence of keywords, and co-citation of journals using the VOSviewer algorithm in the construction of bibliometric maps. This systematic review analysis of 357 documents, including original and review articles, revealed studies inspired by lipase enzymes in the research period, showing that the development of research, together with different areas of knowledge, presents good results related to the applications of lipases, due to information synchronization. Furthermore, this review showed the main challenges in lipase applications regarding increased production and operational stability; establishing well-defined evaluation criteria, such as cultivation conditions, activity, biocatalyst stability, type of support and reactor; thermodynamic studies; reuse cycles; and it can assist in defining goals for the development of successful large-scale applications, showing several points for improvement of future studies on lipase enzymes.

Producing Natural Flavours from Isoamyl Alcohol and Fusel Oil by Using Immobilised Rhizopus oryzae Lipase

Enzymatic synthesis of short-chain esters (flavours) might enable their labelling as natural, increasing their value. Covalently immobilised Rhizopus oryzae lipase (EO-proROL) was used to synthesise isoamyl butyrate and acetate. In cyclohexane, the best performer reaction solvent, 1.8 times higher yield of isoamyl butyrate (ca. 100%) than isoamyl acetate (ca. 55%) was obtained. Optimum initial acid concentration (410 mM) and acid:alcohol mole ratio (0.5) were established by a central composite rotatable design to maximise isoamyl butyrate single-batch and cumulative production with reused enzyme. These conditions were used to scale up the esterification (150 mL) and to assess yield, initial esterification rate, productivity and enzyme operational stability. Commercial isoamyl alcohol and fusel oil results were found to be similar as regards yield (91% vs. 84%), initial reaction rate (5.4 µM min−1 with both substrates), operational stability (40% activity loss after five runs with both) and productivity (31.09 vs. 28.7 mM h−1). EO-proROL specificity for the structural isomers of isoamyl alcohol was also evaluated. Thus, a successful biocatalyst and product conditions ready to be used for isoamyl ester industrial production are here proposed.

Chemical modification of lipases: A powerful tool for activity improvement

The demand for adequate and ecologically acceptable procedures to produce the most differentiated products has been growing in recent decades, with enzymes being excellent examples of the advances achieved so far. Lipases are astonishing catalysts with a vast range of applications including the synthesis of esters, flavours, biodiesel, and polymers. The broad specificity of the substrates, as well as the regio-, stereo-, and enantioselectivity, are the differentiating factors of these enzymes. Structural modification is a current approach to enhance the activity of lipases. Chemical modification of lipases to improve catalytic performance is of great interest considering the increasingly broad fields of application. Together with the physical immobilization onto solid supports, different strategies have been developed to produce catalysts with higher activity and stability. In this review, practical insights into the different strategies developed in recent years regarding the modification of lipases are described. For the first time, the impact of the modifications on the activity and stability of lipases, as well as on the biotechnological applications, is fully compiled. This article is protected by copyright. All rights reserved.

Synthesis of N-Heteroarenemethyl Esters via C–C Bond Cleavage of Acyl Cyanides Under Transition Metal-Free Conditions

A practical method to synthesize N-heteroaryl esters from N-heteroaryl methanols with acyl cyanides via C–C bond cleavage without using any transition metal is demonstrated here. The use of Na₂CO₃/15-crown-5 couple enables access to a series of N-heteroaryl esters in high efficiency. This protocol is operationally simple and highly environmentally benign producing only cyanides as byproducts.

Evaluation of gem-Diacetates as Alternative Reagents for Enzymatic Regio- and Stereoselective Acylation of Alcohols

Geminal diacetates have been used as sustainable acyl donors for enzymatic acylation of chiral and nonchiral alcohols. Especially, it was revealed that geminal diacetates showed higher reactivity than vinyl acetate for hydrolases that are sensitive to acetaldehyde. Under optimized conditions for enzymatic acylation, several synthetically relevant saturated and unsaturated acetates of various primary alcohols were obtained in very high yields up to 98% without E/Z isomerization of the double bond. Subsequently, the acyl donor was recreated from the resulting aldehyde and reused constantly in acylation. Therefore, the developed process is characterized by high atomic efficiency. Moreover, it was shown that acylation using geminal diacetates resulted in remarkable regioselectivity by discriminating among the primary and secondary hydroxyl groups in 1-phenyl-1,3-propanediol providing exclusively 3-acetoxy-1-phenyl-propan-1-ol in good yield. Further, enzymatic kinetic resolution (EKR) and chemoenzymatic dynamic kinetic resolution (DKR) protocols were developed using geminal diacetate as an acylating agent, resulting in chiral acetates in high yields up to 94% with enantiomeric excesses exceeding 99%.

Adaptive responses of Kluyveromyces marxianus CCT 7735 to 2-phenylethanol stress: Alterations in membrane fatty-acid composition, ergosterol content, exopolysaccharide production and reduction in reactive oxygen species

2-phenylethanol (2-PE) is a higher aromatic alcohol with a rose-like aroma used in the cosmetic and food industries as a flavoring and displays potential for application as an antifungal. Biotechnological production of 2-PE from yeast is an interesting alternative due to the non-use of toxic compounds and the generation of few by-products. Kluyveromyces marxianus CCT 7735 is a thermotolerant strain capable of producing high 2-PE titers from L-Phenylalanine; however, like other yeast species, its growth has been strongly inhibited by this alcohol. Herein, we aimed to evaluate the effect of 2-PE on cell growth, cell viability, membrane permeability, glucose uptake, metabolism, and morphology in K. marxianus CCT 7735, as well as its adaptive responses. The stress condition was imposed after 4 h of cultivation by adding 3.0 g.L^-1 of 2-PE in exponential growing cells. 2-PE stress impaired yeast growth, glucose uptake, fermentative metabolism, membrane permeability, and cell viability. Moreover, the stress condition provoked changes in both morphology and surface roughness. The reactive oxygen species (ROS) increased immediately on exposure to 2-PE. Changes in membrane fatty-acid composition, ergosterol content, exopolysaccharides production, and reduction of the ROS levels appear to be the result of adaptive responses in K. marxianus. Our results provided insights into a better understanding of the effects of 2-PE on K. marxianus and its adaptive responses.

Rhizopus oryzae Lipase, a Promising Industrial Enzyme: Biochemical Characteristics, Production and Biocatalytic Applications

Lipases are biocatalysts with a significant potential to enable a shift from current pollutant manufacturing processes to environmentally sustainable approaches. The main reason of this prospect is their catalytic versatility as they carry out several industrially relevant reactions as hydrolysis of fats in water/lipid interface and synthesis reactions in solvent-free or non-aqueous media such as transesterification, interesterification and esterification. Because of the outstanding traits of Rhizopus oryzae lipase (ROL), 1,3-specificity, high enantioselectivity and stability in organic media, its application in energy, food and pharmaceutical industrial sector has been widely studied. Significant advances have been made in the biochemical characterisation of ROL particularly in how its activity and stability are affected by the presence of its prosequence. In addition, native and heterologous production of ROL, the latter in cell factories like Escherichia coli, Saccharomyces cerevisiae and Komagataella phaffii (Pichia pastoris), have been thoroughly described. Therefore, in this review, we summarise the current knowledge about R. oryzae lipase (i) biochemical characteristics, (ii) production strategies and (iii) potential industrial applications.

Scalable Green Approach Toward Fragrant Acetates

The advantageous properties of ethylene glycol diacetate (EGDA) qualify it as a useful substitute for glycerol triacetate (GTA) for various green applications. We scrutinised the lipase-mediated acetylation of structurally diverse alcohols in neat EGDA furnishing the range of naturally occurring fragrant acetates. We found that such enzymatic system exhibits high reactivity and selectivity towards activated (homo) allylic and non-activated primary/secondary alcohols. This feature was utilised in the scalable multigram synthesis of fragrant (Z)-hex-3-en-1-yl acetate in 70% yield. In addition, the Lipozyme 435/EGDA system was also found to be applicable for the chemo-selective acetylation of (hydroxyalkyl) phenols as well as for the kinetic resolution of chiral secondary alcohols. Lastly, its discrimination power was demonstrated in competitive experiments of equimolar mixtures of two isomeric alcohols. This enabled the practical synthesis of 1-pentyl acetate isolated as a single product in 68% yield from the equimolar mixture of 1-pentanol and 3-pentanol.

Continuous Production of 2-Phenylethyl Acetate in a Solvent-Free System Using a Packed-Bed Reactor with Novozym® 435

2-Phenylethyl acetate (2-PEAc), a highly valued natural volatile ester, with a rose-like odor, is widely added in cosmetics, soaps, foods, and drinks to strengthen scent or flavour. Nowadays, 2-PEAc are commonly produced by chemical synthesis or extraction. Alternatively, biocatalysis is a potential method to replace chemical synthesis or extraction for the production of natural flavour. Continuous synthesis of 2-PEAc in a solvent-free system using a packed bed bioreactor through immobilized lipase-catalyzed transesterification of ethyl acetate (EA) with 2-phenethyl alcohol was studied. A Box–Behnken experimental design with three-level-three-factor, including 2-phenethyl alcohol (2-PE) concentration (100–500 mM), flow rate (1–5 mL min−1) and reaction temperature (45–65 °C), was selected to investigate their influence on the molar conversion of 2-PEAc. Then, response surface methodology and ridge max analysis were used to discuss in detail the optimal reaction conditions for the synthesis of 2-PEAc. The results indicated both 2-PE concentration and flow rate are significant factors in the molar conversion of 2-PEAc. Based on the ridge max analysis, the maximum molar conversion was 99.01 ± 0.09% under optimal conditions at a 2-PE concentration of 62.07 mM, a flow rate of 2.75 mL min−1, and a temperature of 54.03 °C, respectively. The continuous packed bed bioreactor showed good stability for 2-PEAc production, enabling operation for at least 72 h without a significant decrease of conversion.

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.