Understanding the high l-valine production in Corynebacterium glutamicum VWB-1 using transcriptomics and proteomics

Hailing Zhang,Xiaoyuan Wang,Chenhui Wang,Yanyan Li

doi:10.1038/s41598-018-21926-5

Abstract

Toward the elucidation of the advanced mechanism of l-valine production by Corynebacterium glutamicum, a highly developed industrial strain VWB-1 was analyzed, employing the combination of transcriptomics and proteomics methods. The transcriptional level of 1155 genes and expression abundance of 96 proteins were changed significantly by the transcriptome and proteome comparison of VWB-1 and ATCC 13869. It was indicated that the key genes involved in the biosynthesis of l-valine, ilvBN, ilvC, ilvD, ilvE were up-regulated in VWB-1, which together made prominent contributions in improving the carbon flow towards l-valine. The l-leucine and l-isoleucine synthesis ability were weakened according to the down-regulation of leuB and ilvA. The up-regulation of the branched chain amino acid transporter genes brnFE promoted the l-valine secretion capability of VWB-1. The NADPH and ATP generation ability of VWB-1 were strengthened through the up-regulation of the genes involved in phosphate pentose pathway and TCA pathway. Pyruvate accumulation was achieved through the weakening of the l-lactate, acetate and l-alanine pathways. The up-regulation of the genes coding for elongation factors and ribosomal proteins were beneficial for l-valine synthesis in C. glutamicum. All information acquired were useful for the genome breeding of better industrial l-valine producing strains.

Highlights

Corynebacterium glutamicum (C. glutamicum) was isolated in 1957 by Kinoshita and coworkers in a screening program for l-glutamate producing bacteria from a soil sample collected at Ueno Zoo in Tokyo (Japan), it turned out to be a natural producer of L-glutamate under biotin limitation[1]
C. glutamicum VWB-1 is a l-valine high-yield strain screened by multiple rounds of random mutagenesis, which led to the differential regulation patterns between VWB-1 and ATCC 13869, both in transcription and translation level
The glucose utilization of VWB-1 was slower than ATCC 13869 at the beginning, and later it surpassed that of ATCC 13869 with the arrival of late logarithmic and stationary phase, this might be due to the larger production of amino acids, especially the production of l-valine, largely increased the physiological demand of glucose

Summary

Introduction

Corynebacterium glutamicum (C. glutamicum) was isolated in 1957 by Kinoshita and coworkers in a screening program for l-glutamate producing bacteria from a soil sample collected at Ueno Zoo in Tokyo (Japan), it turned out to be a natural producer of L-glutamate under biotin limitation[1]. While previous studies focused on specific genes or enzymes to enhance the l-valine biosynthesis ability of C. glutamicum from the viewpoint of carbon metabolic flux enhancement[8,16,17], branched-chain amino acid transportation[18] and cofactors supply project[19]. All those methods have played a certain role in the process of improving the yield of l-valine, the regulation of l-valine metabolism in C. glutamicum is a much more complex process. Transcriptional profiling and two-dimensional gel electrophoresis, which allows us to fully understand the deep mechanism of l-valine biosynthesis and other cell growth and metabolism regulation type correlated to it

Methods

Results

Conclusion