Newly isolated Corynebacterium glutamicum strain PP80 for use in high-temperature L-glutamic acid fermentation

High-temperature fermentation is a strategy to increase the fermentation rates and process stability while reducing cooling costs; however, metabolic heat generated during large-scale cultivations can impair cell growth and product formation. To address this bottleneck, we sought high-temperature L-glutamic acid fermentation processes using naturally thermotolerant Corynebacterium strains as alternatives to experimentally evolved strains. We isolated Corynebacterium glutamicum PP80 from soil in Thailand and evaluated its performance in penicillin-triggered L-glutamic acid fermentation at elevated temperatures. Compared with the type strain C. glutamicum KY9002 (ATCC 13032) and other isolates, including the thermotolerant species Corynebacterium suranareeae N24, PP80 maintained higher fermentation performance at 37-39°C, producing more than 40 g/L L-glutamic acid in jar fermentor cultures. PP80 also retained higher cell viability than KY9002 after penicillin treatment. Although penicillin induced membrane vesicle production in both strains, PP80 showed a smaller penicillin-associated increase in phospholipid-rich membrane vesicles than KY9002. A focused comparison of proteins associated with stress responses, cell-envelope biogenesis, and L-glutamic acid metabolism and export showed broad conservation of the canonical pathways but identified candidate differences, including an additional MscCG2-like protein in PP80. The results identify PP80 as a candidate strain for further evaluation in elevated-temperature L-glutamic acid fermentation.