Production of 7,8-Dihydroxy Unsaturated Fatty Acids from Plant Oils by Whole Recombinant Cells Expressing 7,8-Linoleate Diol Synthase from Glomerella cingulata

Expression, purification and characterization of a dual function α-dioxygenase/peroxidase from Mycolicibacterium smegmatis

An open reading frame from the actinobacterium Mycolicibacterium smegmatis annotated as a Prostaglandin H Synthase (PGHS) was expressed with an N-terminal (his)6 tag and purified to homogeneity. The enzyme has a monomeric molecular weight of 68.3 kD and exists as a dimer in the presence of nonionic detergent. The enzyme uses saturated and unsaturated fatty acids as substrates and catalyzes two reactions: the addition of molecular oxygen alpha to the carboxylate group to form the 2-hydroperoxy fatty acid, followed by reduction to the 2-hydroxy fatty acid. The initial reduction reaction does not require a source of electrons, but electrons must be provided from an appropriate donor such as epinephrine for the reduction reaction to go to completion. Minor reaction products one carbon atom shorter than the original fatty acid substrate are also observed; These most likely arise from the spontaneous decarboxylation of the 2-hydroperoxy fatty acid product to form an aldehyde. This dual function dioxygenase/peroxidase is unusual among the lipid dioxygenases and may represent a bacterial precursor to mammalian PGHS.

Unveiling the biological activities of the microbial long chain hydroxy fatty acids as dual agonists of GPR40 and GPR120

The physiological functions of various fatty acid-originating metabolites from foods and fermented products remained mostly untouched. Thereby, this study examined the biological activities of hydroxy fatty acids as agonists of G protein-coupled receptors (i.e., GPR40 and GPR120), which are derived from long-chain fatty acids (e.g., oleic acid and linoleic acid) by microbiota. Cell-based Ca2+ mobilization assays and in silico docking simulations revealed that not only the degree of unsaturation but also the number and position of hydroxyl groups played a key role in their agonist activities. For instance, 8,11-dihydroxyoctadec-9Z-enoic acid exhibited significantly greater Ca2+ response in the GPR40/GPR120-expressing cells as compared to the endogenous agonists (e.g., linoleic acid and docosahexaenoic acid), forming hydrogen bond interactions with residues in the ligand-binding pockets of receptors. This study will contribute to understanding the relationships between fatty acid structures and agonist activities.

Review of key issues and potential strategies in bio-degradation of polyolefins

Polyolefins are the most widely used plastic product and a major contributor to white pollution. Currently, studies on polyolefin degradation systems are mainly focused on microorganisms and some redox enzymes, and there is a serious black-box phenomenon. The use of polyolefin-degrading enzymes is limited because of the small number of enzymes; in addition, the catalytic efficiency of these enzymes is poor and their catalytic mechanism is unclear, which leads to the incomplete degradation of polyolefins to produce microplastics. In this review, three questions are addressed: the generation and degradation of action targets that promote the degradation of polyolefins, the different modes by which enzymes bind substrates and their application scenarios, and possible multienzyme systems in a unified system. This review will be valuable for mining or modifying polyolefin degradation enzymes and constructing polyolefins degradation systems and may provide novel ideas and opportunities for polyolefin degradation.

Production of 8,11-dihydroxy fatty acids from oleic and palmitoleic acids by Escherichia coli cells expressing variant 6,8-linoleate diol synthases from Penicillium oxalicum

Recombinant Escherichia coli cells expressing 8,11-linoleate diol synthase (LDS) from Penicillium chrysogenum convert oleic and palmitoleic acids to 8-hydroperoxy-9(Z)-octadecenoic acid (HPOME) and 8-hydroperoxy-9(Z)-hexadecenoic acid (HPHME) only, respectively. However, recombinant E. coli cells expressing Q889A variant 6,8-LDS from Penicillium oxalicum as an 8,11-LDS converted oleic and palmitoleic acids to 8,11-dihydroxy-9(Z)-octadecenoic acid (DiHOME) and 8,11-dihydroxy-9(Z)-hexadecenoic acid (DiHHME), respectively, which were identified using LC-MS/MS analysis. To select suitable variants for producing these compounds, position 889 of 6,8-LDS from P. oxalicum was substituted with other amino acids, and recombinant E. coli cells expressing Q889L and Q889A variants were chosen as the best biocatalysts for producing 8,11-DiHOME and 8,11-DiHHME, respectively. The optimal conditions for producing 8,11-DiHOME or 8,11-DiHHME using cells expressing Q889L or Q889A variant 6,8-LDS were pH 6.5 and 30 °C with 5% (v/v) dimethyl sulfoxide (DMSO), 60 g L^-1 cells, and 10 g L^-1 oleic acid or 7.5 g L^-1 palmitoleic acid, respectively. Under these conditions, 10.7 g L^-1 8,11-DiHOME and 8.1 g L^-1 8,11-DiHHME were produced for 1.5 h with molar yields of 96.4 and 96.2% and productivities of 7.1 and 5.4 g L^-1  h^-1 , respectively. The molar yields and concentrations of 8,11-DiHOME and 8,11-DiHHME were highest among those of other reported DiHOMEs and DiHHMEs. To the best of our knowledge, this is the first quantitative production of 8,11-DiHOME and 8,11-DiHHME. This article is protected by copyright. All rights reserved.

Biosurfactants, natural alternatives to synthetic surfactants: Physicochemical properties and applications

Biosurfactants comprise a wide array of amphiphilic molecules synthesized by plants, animals, and microbes. The synthesis route dictates their molecular characteristics, leading to broad structural diversity and ensuing functional properties. We focus here on low molecular weight (LMW) and high molecular weight (HMW) biosurfactants of microbial origin. These are environmentally safe and biodegradable, making them attractive candidates for applications spanning cosmetics to oil recovery. Biosurfactants spontaneously adsorb at various interfaces and self-assemble in aqueous solution, resulting in useful physicochemical properties such as decreased surface and interfacial tension, low critical micellization concentrations (CMCs), and ability to solubilize hydrophobic compounds. This review highlights the relationships between biosurfactant molecular composition, structure, and their interfacial behavior. It also describes how environmental factors such as temperature, pH, and ionic strength can impact physicochemical properties and self-assembly behavior of biosurfactant-containing solutions and dispersions. Comparison between biosurfactants and their synthetic counterparts are drawn to illustrate differences in their structure-property relationships and potential benefits. Knowledge of biosurfactant properties organized along these lines is useful for those seeking to formulate so-called green or natural products with novel and useful properties.