The antimicrobial mechanism of plasma-activated lactic acid on spores of the specific spoilage bacteria from mildly processed crayfish

Abstract

Bacterial spores in food exhibit strong resistance to conventional processing methods, posing a significant challenge to food safety. This scientific aim of the study was to compare the antimicrobial effects of organic acids and plasma-activated lactic acid (PALA) on the specific spoilage bacteria (SSB) spores in cooked crayfish (Procambarus clarkii), and further explored the antimicrobial mechanism of PALA against Bacillus cereus spores. Plasma activation enhanced the antimicrobial efficacy of lactic acid (LA), as 1 % PALA showed equivalent antimicrobial efficacy to 1.5 % LA against spores. Microstructural changes and leakage of core contents indicated that PALA treatment caused damage to the inner membrane (IM) of B. cereus spores. Then, the spore germination experiments further revealed that PALA treatment disrupted the function of SpoVA proteins in the IM, leading to a significant decrease in spore germination capacity. Furthermore, inactivated spores did not regain viability after treatment with lysozyme or Ca-DPA, and no mutants were detected among the surviving spores. These results demonstrated that the inactivation effect of PALA on B. cereus spores is closely related to the structural disruption and dysfunction of the spore IM. Additionally, PALA treatment extended the shelf life and maintained the product quality of cooked crayfish, supporting PALA as a promising measure for controlling microbial safety.