Metabolic engineering ofEscherichia colifor efficient production of (3R)-acetoin

Abstract

BACKGROUND Optically pure acetoin is an important potential pharmaceutical intermediate. It has also been widely used to synthesize novel optically active α-hydroxyketone derivatives and liquid crystal composites. Recombinant Escherichia coli was developed for efficient (3R)-acetoin production. Culture medium optimization and process control were carried out to improve (3R)-acetoin yield by the engineered strain. RESULTS A synthetic pathway involved the budRAB genes from Serratia marcescens and NADH oxidase gene from Lactobacillus brevis in E. coli was developed for efficient (3R)-acetoin production. Batch culture showed that 23.4 g L−1 of (3R)-acetoin could be obtained from 60 g L−1 glucose by the engineered strain. Chiral-column GC analysis indicated that the stereoisomeric purity of (3R)-acetoin produced was 97.3%. Further, the medium composition was optimized in shake flasks by an orthogonal design method. Under optimal conditions, (3R)-acetoin concentration reached 38.3 g L−1 in flask fermentation. Fed-batch fermentation based on a suitable agitation speed was carried out in a 5 L bioreactor, and maximum (3R)-acetoin concentration of 60.3 g L−1 was achieved with a productivity of 1.55 g L−1 h−1 and yield 86.3%. CONCLUSION An engineering E. coli for efficient (3R)-acetoin production was constructed. The optimization of fermentation variables and fed-batch culture resulted in a maximum (3R)-acetoin concentration of 60.3 g L−1. © 2013 Society of Chemical Industry