Metabolic engineering of Serratia marcescens MG1 for enhanced production of (3R)-acetoin.

Fangmin Bai,Liaoyuan Zhang,Lu Dai,Xin Lv,Yaling Shen,Zhanqing Wang

doi:10.1186/s40643-016-0128-2

Abstract

BackgroundOptically pure acetoin (AC) is an important platform chemical which has been widely used to synthesize novel optically active α-hydroxyketone derivatives and liquid crystal composites.ResultsIn this study, slaC and gldA encoding meso-2,3-butanediol dehydrogenase (meso-2,3-BDH) and glycerol dehydrogenase (GDH), respectively, in S. marcescens MG1 were knocked out to block the conversion from AC to 2,3-butanediol (2,3-BD). The resulting strain MG14 was found to produce a large amount of optically pure (3R)-AC with a little 2,3-BD, indicating that another enzyme responsible for 2,3-BD formation except meso-2,3-BDH and GDH existed in the strain MG1. Furthermore, SlaR protein, a transcriptional activator of AC cluster, was overexpressed using P C promoter in the strain MG14, leading to enhancement of the (3R)-AC yield by 29.91%. The recombinant strain with overexpression of SlaR, designated as S. marcescens MG15, was used to perform medium optimization for improving (3R)-AC production.ConclusionUnder the optimized conditions, 39.91 ± 1.35 g/l (3R)-AC was produced by strain MG15 with the productivity of 1.11 g/l h and the conversion rate of 80.13%.

Highlights

Pure acetoin (AC) is an important platform chemical which has been widely used to synthesize novel optically active α-hydroxyketone derivatives and liquid crystal composites
A lot of microbials have been reported to be capable of producing a large amount of AC, such as Klebsiella pneumonia (Wang et al 2015), Bacillus subtilis (Zhang et al 2013a), Enterobacter cloacae (Zhang et al 2016), and Paenibacillus polymyxa (Zhang et al 2012)
As shown in the study of Rao et al (2012), S. marcescens MG1 produced 42.5 g/l 2,3-BD under 24 h of flask fermentation using sucrose as the substrate, while only 4.6 g/l of AC was accumulated during the fermentation process

Summary

Introduction

Pure acetoin (AC) is an important platform chemical which has been widely used to synthesize novel optically active α-hydroxyketone derivatives and liquid crystal composites. A lot of microbials have been reported to be capable of producing a large amount of AC, such as Klebsiella pneumonia (Wang et al 2015), Bacillus subtilis (Zhang et al 2013a), Enterobacter cloacae (Zhang et al 2016), and Paenibacillus polymyxa (Zhang et al 2012). None of these strains had the ability to produce optically pure (3R)-AC or (3S)-AC. S. marcescens was chosen to be the candidate to produce optically pure AC with high concentration in this study

Methods

Results

Conclusion