Efficient synthesis of D-pantolactone in monophase and organic-aqueous biphase reaction biosystem using a novel conjugated polyketide reductase based on integrated substrate pocket alteration

Abstract

D-pantolactone (D-PL) is the crucial chiral intermediate for the synthesis of D-pantothenic acid. The asymmetric synthesis of D-PL from ketopantothenic acid lactone (KPL) using conjugated polyketide reductases (CPRs) exhibited high catalytic efficiency and high enantioselectivity. A novel conjugated polyketide reductase KbCPR was isolated from Kazachstania barnettii and the mutant KbCPRY29K/R65N/K215R was developed with the improved activity by 9.0 folds and the enhanced kcat/Km value by 2.6 folds than the wild-type based on integrated substrate pocket alteration strategy, to alter the substrate channel, to regulate the pocket size, and to facilitate proton transfer. An organic-aqueous biphase biosystem containing 40% dibutyl phthalate (v/v) was constructed to inhibit the hydrolysis of KPL and improve the catalytic efficiency. The time-space yield of 892.9 g/L d−1was achieved, which was higher than ever reported. Furthermore, the organic-aqueous biphase system was employed for the first time in the multi-enzymatic system for D-PL preparation from L-pantolactone (L-PL), without any accumulation of KPL intermediate, high concentration of 1 M L-PL was 95.5% converted to D-PL, with the final production e.e. of > 99.9%.