Improving CoQ10 productivity by strengthening glucose transmembrane of Rhodobacter sphaeroides

Yuying Yang,Haoyu Sun,Zhengliang Qi,Lu Li,Zhen Li,Xinli Liu

doi:10.1186/s12934-021-01695-z

Abstract

BackgroundSeveral Rhodobacter sphaeroides have been widely applied in commercial CoQ10 production, but they have poor glucose use. Strategies for enhancing glucose use have been widely exploited in R. sphaeroides. Nevertheless, little research has focused on the role of glucose transmembrane in the improvement of production.ResultsThere are two potential glucose transmembrane pathways in R. sphaeroides ATCC 17023: the fructose specific-phosphotransferase system (PTSFru, fruAB) and non-PTS that relied on glucokinase (glk). fruAB mutation revealed two effects on bacterial growth: inhibition at the early cultivation phase (12–24 h) and promotion since 36 h. Glucose metabolism showed a corresponding change in characteristic vs. the growth. For ΔfruAΔfruB, maximum biomass (Biomax) was increased by 44.39% and the CoQ10 content was 27.08% more than that of the WT. glk mutation caused a significant decrease in growth and glucose metabolism. Over-expressing a galactose:H+ symporter (galP) in the ΔfruAΔfruB relieved the inhibition and enhanced the growth further. Finally, a mutant with rapid growth and high CoQ10 titer was constructed (ΔfruAΔfruB/tac::galPOP) using several glucose metabolism modifications and was verified by fermentation in 1 L fermenters.ConclusionsThe PTSFru mutation revealed two effects on bacterial growth: inhibition at the early cultivation phase and promotion later. Additionally, biomass yield to glucose (Yb/glc) and CoQ10 synthesis can be promoted using fruAB mutation, and glk plays a key role in glucose metabolism. Strengthening glucose transmembrane via non-PTS improves the productivity of CoQ10 fermentation.

Highlights

Glucose is a common monosaccharide that is available in abundance
Potential glucose transmembrane pathways for R. sphaeroides ATCC 17023 By retrieving the NCBI database, the only integral phosphotransferase system (PTS), fructose-specific PTS (PTSFru), was found in the genome of R. sphaeroides ATCC 17023, which is encoded by the gene cluster fruAB (RSP_1788 and RSP_1786). fruB encodes enzyme I (EI) and HPr, the two sugar-nonspecific protein constituents of the PTS, and fruA encodes the sugarspecific transporter
It was reported that PTSFru encoded by fruAB simultaneously had a function of glucose transmembrane in some E. coil strains [6]

Summary

Introduction

Glucose is a common monosaccharide that is available in abundance. As glucose is cheap and easy to use for microorganisms, it can serve as an ideal source of carbon for producing high-value products, such as C oQ10, throughYang et al Microb Cell Fact (2021) 20:207 free diffusion and must rely on a transporter to cross the cell membrane [6]. Microorganisms depend on more than one system to transport exogenous glucose; the glucose transmembrane mechanisms for E. coli have been widely investigated [6, 7]. E. coli can use two pathways for glucose transmembrane: phosphoenolpyruvate (PEP): carbohydrate phosphotransferase system (PTS) and non-PTS [6]. EIIs are sugar-specific transporters connecting the common PEP/EI/HPr phosphoryl transfer pathway. Use of glucose through the ABC transporter requires extra ATP for glucose phosphorylation in the carbohydrate kinase reaction [6, 10]. P TSGlc is a preferred channel for transferring exogenous glucose into cells in industrial bacteria, such as E. coli, Bacillus subtilis, and Corynebacterium glutamicum [4, 11, 12]. Little research has focused on the role of glucose transmembrane in the improvement of production

Methods

Results

Conclusion