Enhancing acid production of Acetobacter pasteurianus by laser and intense pulsed light mutagenesis and its molecular mechanism based on transcriptomic analysis

In this study, novel mutagenesis of He–Ne laser and intense pulsed light (IPL) combined with high-throughput screening (HTS) method were used to mutagenize Acetobacter pasteurianus CGMCC 1.59. The acid production of mutants 1-F-6 (after 50 min of He–Ne laser mutagenesis) and 1-C-1 (after 60 min of IPL mutagenesis) was observably increased by 18.21% and 8.41%, respectively, with reference to CGMCC 1.59 (58.75 g·L−1). Transcriptomics and quantitative real-time PCR (qRT-PCR) results indicated that A-vs-C had 17 differentially expressed genes (DEGs) (15 up-regulated and 2 down-regulated), whereas A-vs-F showed 132 DEGs (58 up-regulated and 74 down-regulated). The annotated signaling pathways were significantly enriched in carbohydrate metabolism, growth, amino acid metabolism, and carbohydrate metabolism. The mutant 1-C-1 only up-regulated the expression of pyruvate metabolism pathways and tricarboxylic acid (TCA) cycle-related genes, while mutant 1-F-6 up-regulated the expression of ethanol oxidation respiratory chain pathway-related genes in addition to alterations in the above pathways. Acetaldehyde dehydrogenase and alcohol dehydrogenase were the main acting enzyme systems in the acetic acid fermentation process, and their up-regulation helped to increase acid production. Also, the enhancement of TCA cycle and oxidative respiratory chain pathways could improve its energy metabolism pathways, thereby promoting the acid production of acetic acid bacteria.