Pushing the limits: Cyclodextrin-based intensification of bioreductions

Efficient Synthesis of Chiral Aryl Alcohol with a Novel Kosakonia radicincitans Isolate in Tween 20/L-carnitine: Lysine-Containing Synergistic Reaction System

Chiral trifluoromethyl alcohols as vital intermediates are of great interest in fine chemicals and especially in pharmaceutical synthesis. In this work, a novel isolate Kosakonia radicincitans ZJPH202011 was firstly employed as biocatalyst for the synthesis of (R)-1-(4-bromophenyl)-2,2,2-trifluoroethanol ((R)-BPFL) with good enantioselectivity. By optimizing fermentation conditions and bioreduction parameters in aqueous buffer system, the substrate concentration of 1-(4-bromophenyl)-2,2,2-trifluoroethanone (BPFO) was doubled from 10 to 20 mM, and the enantiomeric excess (ee) value for (R)-BPFL increased from 88.8 to 96.4%. To improve biocatalytic efficiency by strengthening the mass-transfer rate, natural deep-eutectic solvents, surfactants and cyclodextrins (CDs) were introduced separately in the reaction system as cosolvent. Among them, L-carnitine: lysine (C: Lys, molar ratio 1:2), Tween 20 and γ-CD manifested higher (R)-BPFL yield compared with other same kind of cosolvents. Furthermore, based on the excellent performance of both Tween 20 and C: Lys (1:2) in enhancing BPFO solubility and ameliorating cell permeability, a Tween 20/C: Lys (1:2)-containing integrated reaction system was then established for efficient bioproduction of (R)-BPFL. After optimizing the critical factors involved in BPFO bioreduction in this synergistic reaction system, BPFO loading increased up to 45 mM and the yield reached 90.0% within 9 h, comparatively only 37.6% yield was acquired in neat aqueous buffer. This is the first report on K. radicincitans cells as new biocatalyst applied in (R)-BPFL preparation, and the developed Tween 20/C: Lys-containing synergistic reaction system has great potential for the synthesis of various chiral alcohols.

Selective immobilization of his-tagged phosphomannose isomerase on Ni chelated nanoparticles with good reusability and activity

In this paper, self-stable precipitation polymerization was used to prepare the enzyme-immobilized microsphere composite. Phosphomannose isomerase (PMI) with His-tag was successfully immobilized on Ni 2+ charged pyridine-derived particles. The maximum amount of PMI immobilized on such particles was ~ 184 mg/g. Compared with the free enzymes, the activity of the immobilized enzymes has been significantly improved. In addition, the immoblized enzymes showed a much better thermostability than free enzymes. At the same time, the immobilized enzymes can be reused for multiple reaction cycles. We have observed that the enzyme activity did not decrease significantly after 6 cycles of repeating usages. We conclude that the pyridine-derived particles can be used to selectively immobilize His-tagged enzymes, which can couple the enzyme purification and catalysis steps and improve the efficiency of enzyme-catalyzed industrial processes.

Reductive enzymatic dynamic kinetic resolution affording 115 g/L (S)-2-phenylpropanol

Background

Published biocatalytic routes for accessing enantiopure 2-phenylpropanol using oxidoreductases afforded maximal product titers of only 80 mM. Enzyme deactivation was identified as the major limitation and was attributed to adduct formation of the aldehyde substrate with amino acid residues of the reductase.

Results

A single point mutant of Candida tenuis xylose reductase (CtXR D51A) with very high catalytic efficiency (43·10³ s⁻¹ M⁻¹) for (S)-2-phenylpropanal was found. The enzyme showed high enantioselectivity for the (S)-enantiomer but was deactivated by 0.5 mM substrate within 2 h. A whole-cell biocatalyst expressing the engineered reductase and a yeast formate dehydrogenase for NADH-recycling provided substantial stabilization of the reductase. The relatively slow in situ racemization of 2-phenylpropanal and the still limited biocatalyst stability required a subtle adjustment of the substrate-to-catalyst ratio. A value of 3.4 g_substrate/g_{cell-dry-weight} was selected as a suitable compromise between product ee and the conversion ratio. A catalyst loading of 40 g_{cell-dry-weight} was used to convert 1 M racemic 2-phenylpropanal into 843 mM (115 g/L) (S)-phenylpropanol with 93.1% ee.

Conclusion

The current industrial production of profenols mainly relies on hydrolases. The bioreduction route established here represents an alternative method for the production of profenols that is competitive with hydrolase-catalyzed kinetic resolutions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-021-00715-5.