Biosynthesis of ethyl butyrate using immobilized lipase: a statistical approach

Thorough Characterization of ETHQB3.5, a QTL Involved in Melon Fruit Climacteric Behavior and Aroma Volatile Composition

The effect of the QTL involved in climacteric ripening ETHQB3.5 on the fruit VOC composition was studied using a set of Near-Isogenic Lines (NILs) containing overlapping introgressions from the Korean accession PI 16375 on the chromosome 3 in the climacteric 'Piel de Sapo' (PS) genetic background. ETHQB3.5 was mapped in an interval of 1.24 Mb that contained a NAC transcription factor. NIL fruits also showed differences in VOC composition belonging to acetate esters, non-acetate esters, and sulfur-derived families. Cosegregation of VOC composition (23 out of 48 total QTLs were mapped) and climacteric ripening was observed, suggesting a pleiotropic effect of ETHQB3.5. On the other hand, other VOCs (mainly alkanes, aldehydes, and ketones) showed a pattern of variation independent of ETHQB3.5 effects, indicating the presence of other genes controlling non-climacteric ripening VOCs. Network correlation analysis and hierarchical clustering found groups of highly correlated compounds and confirmed the involvement of the climacteric differences in compound classes and VOC differences. The modification of melon VOCs may be achieved with or without interfering with its physiological behavior, but it is likely that high relative concentrations of some type of ethylene-dependent esters could be achieved in climacteric cultivars.

A review of synthesis of esters with aromatic, emulsifying, and lubricant properties by biotransformation using lipases

The esterification reactions catalyzed by lipases are among the most significant biochemical processes of industrial relevance. The lipases have the function of versatility by catalyzing a diversity of reactions with extreme ease, obtaining quality products with high yield. Therefore, enzyme-catalyzed esterification has gained increasing attention in many applications, due to the importance of derived products. More specifically, lipase-catalyzed esterification reactions have attracted interest in research over the past decade, due to the increased use of organic esters in the chemical and biotechnology industry. These esters can be obtained by three techniques: extraction from natural sources, chemical and enzymatic syntheses. Biotechnological processes have offered several advantages and are shown as a competitive alternative to chemical methods due to high catalytic efficiency, mild operating conditions, and selectivity of natural catalysts. These an industrial point of view, reactions catalyzed by enzymes are the most economical approach to achieve green products with no toxicity and no harm to human health. Thus, this review presents a descriptive evaluation of the trends and perspectives applied to enzymatic esterification, mainly for the synthesis of esters with different properties, such as aromatics, emulsifiers, and lubricants using the esterification process. An emphasis is given to essential factors, which affect the lipase-catalyzed esterification reaction. In which, the parameters dependent on the lipase source, a form of the biocatalyst (free or immobilized), the polarity of the reaction medium, the molar ratio between alcohol and acid, among other variables, are also discussed. This article is protected by copyright. All rights reserved.

Chemical Characteristics of Three Kinds of Japanese Soy Sauce Based on Electronic Senses and GC-MS Analyses

Japanese soy sauce has become more acceptable by Chinese consumers due to its umami taste. However, the volatile flavor compounds and taste characters have not been fully clarified. This study aimed to explore the flavor characteristics of three kinds of Japanese soy sauce, including Koikuchi Shoyu, Usukuchi Shoyu, and Amakuchi Shoyu. The secret of volatile flavor substances was investigated by Gas Chromatography-Mass Spectrometry (GC-MS) and electronic nose, while taste compounds were investigated by silylation GC-MS and electronic tongue (E-tongue). A total of 173 volatile flavor substances and 160 taste compounds were identified. In addition, 28 aroma compounds with odor activity values (OAV) ≥ 1 were considered as the typical flavors. We found that alcohols and aldehydes were in high abundance in Japanese soy sauce, but only a small portion of pyrazines and esters were. Based on electronic nose and GC-MS analysis, Koikuchi Shoyu gives more contribution to aroma compounds, while Usukuchi Shoyu and Amakuchi Shoyu give the sourness and sweetness features based on E-tongue and silylation GC-MS analysis. In this study, 50 kinds of sugars were detected that contributed to the sweetness of soy sauce. This study will provide new insight into the flavor characteristics of Japanese soy sauce that potentially contribute to the innovation and development of soy sauce.

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.

Application of response surface methodology (RSM) for optimizing coagulation process of paper recycling wastewater using Ocimum basilicum

The wastewater produced in a pulp and paper industry is one of the most polluted industrial wastewaters, and therefore its treatment requires complex processes. One of the simple and feasible processes in pulp and paper wastewater treatment is coagulation and flocculation. Overusing a chemical coagulant can produce a large volume of sludge and increase costs and health concerns. Therefore, the use of natural and plant-based coagulants has been recently attracted the attention of researchers. One of the advantages of using Ocimum basilicum as a coagulant is a reduction in the amount of chemical coagulant required. In this study, the effect of basil mucilage has been investigated as a plant-based coagulant together with alum for treatment of paper recycling wastewater. Response surface methodology (RSM) was used to optimize the process of chemical coagulation based on a central composite rotatable design (CCRD). Quadratic models for colour reduction and TSS removal with coefficients of determination of R²> 96 were obtained using the analysis of variance. Under optimal conditions, removal efficiencies of colour and total suspended solids (TSS) were 85% and 82%, respectively.

Efficient Enzymatic Preparation of Flavor Esters in Water

A straightforward biocatalytic method for the enzymatic preparation of different flavor esters starting from primary alcohols (e.g., isoamyl, n-hexyl, geranyl, cinnamyl, 2-phenethyl, and benzyl alcohols) and naturally available ethyl esters (e.g., formate, acetate, propionate, and butyrate) was developed. The biotransformations are catalyzed by an acyltransferase from Mycobacterium smegmatis (MsAcT) and proceeded with excellent yields (80-97%) and short reaction times (30-120 min), even when high substrate concentrations (up to 0.5 M) were used. This enzymatic strategy represents an efficient alternative to the application of lipases in organic solvents and a significant improvement compared with already known methods in terms of reduced use of organic solvents, paving the way to sustainable and efficient preparation of natural flavoring agents.

Kinetics Study and Parametric Sensitivity Analysis of Esterification of Butyric Acid with Benzyl Alcohol: A Taguchi Methodology Approach

The liquid phase esterification of butyric acid with benzyl alcohol was studied using homogenous catalyst p-toluenesulfonic acid. The reversible second order rate equation was used to investigate the kinetic parameters of the reaction. The L9 orthogonal array of Taguchi methodology was employed to study the parametric effect independent variables on the responses equilibrium constant (Keq) and conversion (Xeq) of butyric acid. The parameters and their range such as catalyst concentration (0.5–1.5 wt%), temperature (333–363 K) and molar ratio (1–3) was used and considered as independent parameters for parametric sensitivity analysis. Non-ideal behavior of the reaction was studied using UNIFAC group contribution method. The effect of reaction temperature on the overall activity factor was studied. The relative parametric effect on the Keq and Xeq was found. In sensitivity analysis, temperature and molar ratio was the most influencing parameter on the Keq and Xeq. The regression model was developed and validate by performing unknown experiments.

Interaction of a digestive protease, Candida rugosa lipase, with three surfactants investigated by spectroscopy, molecular docking and enzyme activity assay

The extensive use of surfactants in food, laundry products and agriculture has caused concern about their biosafety. However, few studies have been done on their potential effect on the lipase which has always been used with surfactants in food and laundry industry. Herein, we investigated the interaction of three surfactants (sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), sodium lauryl sulfonate (SLS)) with Candida rugosa lipase (CRL), which is a popular biocatalyst used regularly with surfactants. The effect of the three surfactants on the conformation and activity of CRL was evaluated by using multiple spectral methods, enzyme activity assay and molecular docking modeling. The results demonstrated that CRL interacted with SDS, SDBS and SLS primarily through hydrophobic forces, H-bonding and electrostatic forces, respectively. The binding constants (K_A) of SDBS with CRL varied with temperature: 1.99×10³mol/L at 298K and 4.13×10³mol/L at 318K. SDS and SDBS affected the secondary structure and skeleton of CRL, which changed the polarity of CRL and enhanced its activity. SLS also changed the secondary structure and activity of CRL moderately, but had little effect on its polarity and chromophore microenvironment. Accordingly, all three surfactants exhibited effect to CRL on the molecular level calling for more attention to pay on their biosafety. The work demonstrates that SDS, SDBS and SLS could cause negative effects to CRL from different angles and therefore are not bio-friendly detergents.

Lipase catalyzed transesterification of ethyl butyrate synthesis in n-hexane- a kinetic study

Kinetics of lipase catalyzed transesterification of ethyl caprate and butyric acid was investigated. The objective of this work was to propose a reaction mechanism and develop a rate equation for the synthesis of ethyl butyrate by transesterification using surfactant coated lipase from Candida rugosa. The reaction rate could be described in terms of Michaelis-Menten equation with a Ping-Pong Bi-Bi mechanism and competitive inhibition by both the substrates. The values of kinetic parameters computed were V_max = 2.861 μmol/min/mg; K_m(acid) = 0.0746 M; K_m(ester) = 0.125 M; K_i acid = 0.450 M. This study indicated a competitive enzyme inhibition by butyric acid during lipase catalyzed transesterification reaction. Experimental observations had clearly indicated that the substrates as well as product act as dead-end inhibitors.

Preparation, release and physicochemical characterisation of ethyl butyrate and hexanal inclusion complexes with β- and γ-cyclodextrin

Complexes of ethyl butyrate and hexanal encapsulated by β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) were prepared by coprecipitation, and gas chromatography was used to quantity the flavour compounds in the complexes. The ethyl butyrate-γ-CD complex had the highest inclusion ratio (12.20%) followed by the ethyl butyrate-β-CD, hexanal-β-CD and hexanal-γ-CD complexes (11.29, 4.41 and 3.33%, respectively). Release experiments were performed under different relative humidities (RH 93, 75 and 52%) and temperatures (4 and 25 °C). The flavour release behaviours of the complexes were described by the Avrami equation. The rate of flavour release was enhanced with both increasing temperature and RH, although the effect of RH was stronger. Physicochemical characterisation using FT-IR, XRD, DSC and SEM analyses demonstrated that crystalline complexes were formed. Both β-CD and γ-CD were able to encapsulate ethyl butyrate and hexanal, and lower RH and temperature were more suitable for the storage of these complexes.

Enhanced ethyl butyrate production using immobilized lipase

In this study, the production of ethyl butyrate was investigated by using immobilized lipase enzyme in shake flasks. In order to determine optimum conditions for the production, response surface methodology was used. The model indicated the optimum conditions for maximum conversion (9.1%) at the 0.31 M substrate concentration, acid- alcohol molar ratio of 0.49, immobilized enzyme 25% (w/v) at 35°C, for 3 hours which were in good agreement with the experimental value. At the end of the 55 hours conversion was obtained as 61.3%. When Na2HPO4 was used in reaction medium conversion increased to 90.3% for 55 hours.

Lipase catalyzed synthesis of flavor esters in non-aqueous media: Optimization of the yield of pentyl 2-methylpropanoate by statistical analysis

In this study, the synthesis of pentyl 2-methylpropanoate employing a commercial lipase from Candida rugosa was investigated, the emphasis being placed on analyzing the effects of various process conditions on the yield of ester. The response surface methodology (RSM) and five-level-five-factor central composite rotatable design (CCRD) were used to evaluate the effects of variables, namely the initial water content, 0.0-2.0% (w/v), the reaction temperature, 35-75?C, the enzyme concentration, 1.0-5.0 g dm-3, the acid/alcohol mole ratio, 1:2-5:2, and the reaction time, 4-48 h, on the yield (%) of ester. The production of pentyl 2-methylpropanoate was optimized and an ester yield response equation was obtained, enabling the prediction of ester yields from known values of the five main factors. It seems that the enzyme concentration, reaction time and acid/alcohol mole ratio predominantly determine the conversion process, while the amount of added water amount had no significant influence on the ester yield. Conversion of around 92 % of the substrate to ester could be realized using a concentration of lipase as low as 4.0 g dm-3 and in a relatively short time (26 h) at 35?C, when a high substrate mole ratio of 2.5 was used.