Integration of ARTP mutagenesis with biosensor-mediated high-throughput screening to improve L-serine yield in Corynebacterium glutamicum

摘要

l-Serine is widely used in the pharmaceutical, food, and cosmetics industries. Although direct fermentative production of l-serine from sugar in Corynebacterium glutamicum has been achieved, the l-serine yield remains relatively low. In this study, atmospheric and room temperature plasma (ARTP) mutagenesis was used to improve the l-serine yield based on engineered C. glutamicum Delta SSAAI strain. Subsequently, we developed a novel high-throughput screening method using a biosensor constructed based on NCgl0581, a transcriptional factor specifically responsive to l-serine, so that l-serine concentration within single cell of C. glutamicum can be monitored via fluorescence-activated cell sorting (FACS). Novel l-serine-producing mutants were isolated from a large library of mutagenized cells. The mutant strain A36-pDser was screened from 1.2 x 10(5) cells, and the magnesium ion concentration in the medium was optimized specifically for this mutant. C. glutamicum A36-pDser accumulated 34.78 g/L l-serine with a yield of 0.35 g/g sucrose, which were 35.9 and 66.7% higher than those of the parent C. glutamicum Delta SSAAI-pDser strain, respectively. The l-serine yield achieved in this mutant was the highest of all reported l-serine-producing strains of C. glutamicum. Moreover, the whole-genome sequencing identified 11 non-synonymous mutations of genes associated with metabolic and transport pathways, which might be responsible for the higher l-serine production and better cell growth in C. glutamicum A36-pDser. This study explored an effective mutagenesis strategy and reported a novel high-throughput screening method for the development of l-serine-producing strains.