Production of 10S-hydroxy-8(E)-octadecenoic acid from oleic acid by whole recombinant Escherichia coli cells expressing 10S-dioxygenase from Nostoc punctiforme PCC 73102 with the aid of a chaperone

Biocatalytic oxyfunctionalization of unsaturated fatty acids to oxygenated chemicals via hydroxy fatty acids

The selective oxyfunctionalization of unsaturated fatty acids is difficult in chemical reactions, whereas regio- and stereoselective oxyfunctionalization is often performed in biocatalytic synthesis. Fatty acid oxygenases, including hydratases, lipoxygenases, dioxygenases, diol synthases, cytochrome P450 monooxygenases, peroxygenases, and 12-hydroxylases, are used to convert C16 and C18 unsaturated fatty acids to diverse regio- and stereoselective mono-, di-, and trihydroxy fatty acids via selective oxyfunctionalization. The formed hydroxy fatty acids or hydroperoxy fatty acids are metabolized to industrially important oxygenated chemicals such as lactones, green leaf volatiles, and bioplastic monomers, including ω-hydroxy fatty acids, α,ω-dicarboxylic acids, and fatty alcohols, by biocatalysts. For increased oxyfunctionalization of unsaturated fatty acids, enzyme engineering, functional and balanced expression in recombinant cells, selection of suitable catalyst types, and reaction engineering have been suggested. This review describes biocatalysts involved in the oxyfunctionalization of unsaturated fatty acids and the production of hydroxy fatty acids and oxygenated chemicals.

Computational Insights and In Silico Characterization of a Novel Mini-Lipoxygenase from Nostoc Sphaeroides and Its Application in the Quality Improvement of Steamed Bread

Lipoxygenase (EC1.13.11.12, LOX) has been potentially used in the food industry for food quality improvement. However, the low activity, poor thermal stability, narrow range of pH stability, as well as undesirable isoenzymes and off-flavors, have hampered the application of current commercial LOX. In this study, a putative mini-lipoxygenase gene from cyanobacteria, Nostoc sphaeroides (NsLOX), was cloned and expressed in E. coli BL21. NsLOX displayed only 26.62% structural identity with the reported LOX from Cyanothece sp., indicating it as a novel LOX. The purified NsLOX showed the maximum activity at pH 8.0 and 15 °C, with superior stability at a pH range from 6.0 to 13.0, retaining about 40% activity at 40 °C for 90 min. Notably, NsLOX exhibited the highest specific activity of 78,080 U/mg towards linoleic acid (LA), and the kinetic parameters-K_m, k_cat, and k_cat/K_m-attain values of 19.46 μM, 9199.75 s^-1, and 473.85 μM^-1 s^-1, respectively. Moreover, the activity of NsLOX was obviously activated by Ca²⁺, but it was completely inhibited by Zn²⁺ and Cu²⁺. Finally, NsLOX was supplied in steamed bread and contributed even better improved bread quality than the commercial LOX. These results suggest NsLOX as a promising substitute of current commercial LOX for application in the food industry.

Production of 7,10-dihydroxy-8(E)-octadecenoic acid using cell-free supernatant of Pseudomonas aeruginosa

Cell-free synthesis has been adopted in the bioconversion process due to its known advantages, such as fast production rate, high product content, and no substrate/product inhibition effect. In this study, the cell-free supernatant of Pseudomonas aeruginosa was used to improve the production of 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) from oleic acid. DOD production using cell-free supernatant demonstrated reduction in bioconversion duration and higher product concentration than conventional method using whole cell culture. The maximum DOD concentration (6.41 g/L) was obtained after 36 h of biotransformation using 1 % v/v oleic acid as a substrate with a productivity of 0.178 g/L/h and a yield of 74.8 %. DOD concentration, productivity, and yield using cell-free supernatant were 2.12, 7.12, and 2.22 times higher, respectively, than using the conventional whole cell culture method. Of the carbon and nitrogen sources used in pre-culture, galactose and sodium glutamate along with diammonium phosphate were found to be the most effective for DOD production. An incubation temperature of 27 °C and pH 8.0 were found to be most favorable for DOD production. In addition, sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis demonstrated the presence of enzymes related to DOD production in the cell-free supernatant, which was substantiated by performing DOD production experiment using the supernatant enzymes extracted from protein gel bands with oleic acid as a substrate. To the best of our knowledge, this is the first report on DOD production using a cell-free supernatant and verifying the existence of the relevant enzymes in the cell-free supernatant. Compared to whole cell process, cell-free DOD production holds several advantages, including higher DOD productivity which could be beneficial for large-scale production.

Low-Level Organic Solvents Improve Multienzyme Whole-Cell Catalytic Synthesis of Myricetin-7-O-Glucuronide

Multienzyme whole-cell biocatalysts are preferred in industrial applications, and two major concerns regarding the use of these biocatalysts, cell viability and cell membrane integrity, must be addressed. In this work, the transformation of myricetin to myricetin-7-O-glucuronide catalyzed by an engineered Escherichia coli strain was taken as the model reaction to examine the impacts of low-level organic solvents on whole-cell biocatalysis. Low-level organic solvents (2%, v/v) showed a significant increase (roughly 13-fold) in myricetin-7-O-glucuronide yields. No obvious compromises of cellular viability and integrity were observed by a flow cytometry assay or in the determination of extracellular protein leakage, suggesting the addition of low-level organic solvents accommodates whole E. coli cells. Furthermore, a scaled-up reaction was conducted to test the capability and efficiency of whole-cell catalysis in the presence of organic solvents. This study presents a promising and simple means to enhance the productivity of multienzyme whole-cell catalysis without losing the barrier functions of the cell membrane.

Complete Biotransformation of Protopanaxadiol-Type Ginsenosides into 20-O-β-Glucopyranosyl-20(S)-protopanaxadiol by Permeabilized Recombinant Escherichia coli Cells Coexpressing β-Glucosidase and Chaperone Genes

The ginsenoside 20-O-β-glucopyranosyl-20(S)-protopanaxadiol or compound K is an essential ingredient in functional food, cosmetics, and traditional medicines. However, no study has reported the complete conversion of all protopanaxadiol (PPD)-type ginsenosides from ginseng extract into compound K using whole-cell conversion. To increase the production of compound K from ginseng extract using whole recombinant cells, the β-glucosidase enzyme from Caldicellulosiruptor bescii was coexpressed with a chaperone expression system (pGro7), and the cells expressing the coexpression system were permeabilized with ethylenediaminetetraacetic acid. The permeabilized cells carrying the chaperone coexpression system showed a 2.6-fold increase in productivity and yield as compared with nontreated cells, and completely converted all PPD-type ginsenosides from ginseng root extract into compound K with the highest productivity among the results reported so far. Our results will contribute to the industrial biological production of compound K.