A new strategy for enhancement of poly‐γ‐glutamic acid production by multiple physicochemical stresses in Bacillus licheniformis

Abstract

AbstractBACKGROUNDThe physicochemical stress‐induced bioprocess is an efficient strategy for enhancement of the production of microbial metabolites, but multiple physicochemical stresses have not applied in poly‐γ‐glutamic acid (γ‐PGA) production.RESULTSThe effects of multiple physicochemical stresses on the production and synthetase genes transcription of γ‐PGA were investigated in Bacillus licheniformis WX‐02. Under heat stress stimulated at 50 °C, osmotic stress induced by 3% KCl, and alkaline stress mediated by pH 8.5, γ‐PGA yields increased by 66%, 106% and 133%, respectively, and the transcription levels of γ‐PGA synthetase gene PgsC were improved 3.1‐fold, 3.6‐fold and 5.4‐fold compared with the control. Heat and osmotic stress also induced the up‐regulation of another γ‐PGA synthetase gene of PgsB with 1.4‐fold and 4.3‐fold increase, respectively. By combined application of heat and pH stress, the maximum γ‐PGA yield reached 29.34 g L−1, 185% higher than the control.CONCLUSIONThis study provided a novel strategy to enhance γ‐PGA yield by physicochemical stresses treatment, and the possible mechanism was also determined. The stress‐mediated strategy can be easily applied in γ‐PGA production at large scale. © 2014 Society of Chemical Industry