Wickerhamomyces subpelliculosus as whole-cell biocatalyst for stereoselective bioreduction of ketones

Bioreduction of N-(3-oxobutyl)heterocycles with flexible ring by yeast whole-cell biocatalysts

This study explored the bioreduction of N-(3-oxobutyl)heterocycles with (partially) saturated heterocyclic moieties using whole-cell forms of wild-type yeast strains and commercially available baker's yeast (Saccharomyces cerevisiae). Eleven wild-type yeast strains and baker's yeast were screened for ketoreductase activity on a series of five flexible N-heterocycles with prochiral carbonyl group in the N-(3-oxobutyl) substituent. Among the yeast strains tested, Candida parapsilosis (WY12) proved to be the most efficient biocatalyst in the bioreductions, resulting in the corresponding enantiopure alcohols-being promising chiral fragments with high level of drug-likeness-with good to excellent conversions (83-99%) and high enantiomeric excess (ee > 99%). Other strains, such as Pichia carsonii (WY1) and Lodderomyces elongisporus (WY2), also showed promising ketoreductase activities with certain substrates. After screening as lyophilized whole cells, C. parapsilosis cells were immobilized in the form of calcium, zinc, nickel, and copper alginate beads. The whole-cell immobilization enabled recycling, with considerable residual activity of the biocatalyst over multiple cycles. Additionally, the study explored the scalability of these bioreductions, with immobilized C. parapsilosis delivering promising results. The use of immobilized cells simplified the work-up process and resulted in chiral alcohols with similar or even higher conversions to those observed in the screening reactions. Molecular docking of the five flexible N-heterocycles with prochiral carbonyl group into the active site of the experimental structure of the carbonyl reductase of C. parapsilosis rationalized their biocatalytic behavior and confirmed the assigned (S)-configuration of forming enantiopure alcohols. KEY POINTS: • Ketoreductase activity of eleven wild-type yeast strains and baker's yeast were examined. • Candida parapsilosis was subjected to whole-cell immobilization and recycling. • Enantiopure alcohols with flexible N-heterocyclic units were produced at preparative scale.

Enantiocomplementary Bioreduction of 1-(Arylsulfanyl)propan-2-ones

This study explored the enantiocomplementary bioreduction of substituted 1-(arylsulfanyl)propan-2-ones in batch mode using four wild-type yeast strains and two different recombinant alcohol dehydrogenases from Lactobacillus kefir and Rhodococcus aetherivorans. The selected yeast strains and recombinant alcohol dehydrogenases as whole-cell biocatalysts resulted in the corresponding 1-(arylsulfanyl)propan-2-ols with moderate to excellent conversions (60-99%) and high selectivities (ee > 95%). The best bioreductions-in terms of conversion (>90%) and enantiomeric excess (>99% ee)-at preparative scale resulted in the expected chiral alcohols with similar conversion and selectivity to the screening reactions.

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

"Fishing and Hunting"-Selective Immobilization of a Recombinant Phenylalanine Ammonia-Lyase from Fermentation Media

This article overviews the numerous immobilization methods available for various biocatalysts such as whole-cells, cell fragments, lysates or enzymes which do not require preliminary enzyme purification and introduces an advanced approach avoiding the costly and time consuming downstream processes required by immobilization of purified enzyme-based biocatalysts (such as enzyme purification by chromatographic methods and dialysis). Our approach is based on silica shell coated magnetic nanoparticles as solid carriers decorated with mixed functions having either coordinative binding ability (a metal ion complexed by a chelator anchored to the surface) or covalent bond-forming ability (an epoxide attached to the surface via a proper linker) enabling a single operation enrichment and immobilization of a recombinant phenylalanine ammonia-lyase from parsley fused to a polyhistidine affinity tag.

Co-immobilized Whole Cells with ω-Transaminase and Ketoreductase Activities for Continuous-Flow Cascade Reactions

An improved sol-gel process involving the use of hollow silica microspheres as a supporting additive was applied for the co-immobilization of whole cells of Escherichia coli with Chromobacterium violaceum ω-transaminase activity and Lodderomyces elongisporus with ketoreductase activity. The co-immobilized cells with two different biocatalytic activities could perform a cascade of reactions to convert racemic 4-phenylbutan-2-amine or heptan-2-amine into a nearly equimolar mixture of the corresponding enantiomerically pure R amine and S alcohol even in continuous-flow mode. The novel co-immobilized whole-cell system proved to be an easy-to-store and durable biocatalyst.