Draft genome and physiological characterization of a newly isolated L-arabinose-utilizing Corynebacterium glutamicum CS176.

This study reports the physiological and genomic characterization of Corynebacterium glutamicum CS176, a newly isolated strain exhibiting a rare combination of traits: efficient L-arabinose utilization and L-glutamate production without chemical induction, even under excess biotin conditions. Genome analysis of the 3.10 Mb draft sequence (54.20% GC) revealed a 7.8 kb L-arabinose utilization gene cluster highly similar to those of arabinose-assimilating strains, suggesting acquisition via horizontal gene transfer. To link genotype with phenotype, the effects of temperature, oxygen availability, carbon sources, and biotin concentration on bacterial growth and L-glutamate production were systematically evaluated under controlled conditions. Optimal growth was observed at 30-37 °C under high oxygen conditions, whereas maximal L-glutamate production (up to 2.5 g/L in mixed substrates) occurred at 37-39.5 °C under medium-low oxygen conditions. Notably, CS176 maintained L-glutamate production across a wide range of biotin concentrations (0-200 µg/L), in contrast to the typical biotin-dependent regulation observed in C. glutamicum. Furthermore, glucose-arabinose co-utilization enhanced both growth and L-glutamate production, highlighting metabolic flexibility. Together, these findings identify CS176 as a promising strain that overcomes key limitations in conventional glutamate fermentation and provides insights for metabolic engineering and sustainable bioprocess development.