Enhanced heat stable antifungal factor production by Lysobacter enzymogenes OH11 with cheap feedstocks: medium optimization and quantitative determination.

Heat stable antifungal factor (HSAF) is considered to be a potential biological pesticide due to its broad antifungal activity and novel mode of action. However, few studies have reported on HSAF production during fermentation. Thus, this work was executed to optimize the medium composition to maximize HSAF production by Lysobacter enzymogenes OH11, with soybean flour, glucose and CaCl2 identified as suitable nutrients with concentrations of 8·00, 7·89 and 0·72 g l-1 respectively. Simultaneously, the quantitative analysis of HSAF production was established by eliminating the emulsification problem, and the highest HSAF production was determined to be 356·34 ± 13·86 mg l-1 using the optimized medium, 12-fold higher than when using the 10% TSB medium (29·34 ± 2·57 mg l-1 ). Furthermore, the cost of this medium was assessed and nearly 31-fold lower than that of 10% TSB. This study suggests that the optimized medium is not only effective but also economical for HSAF production. SIGNIFICANCE AND IMPACT OF THE STUDY: Significance and Impact of the Study: Heat stable antifungal factor (HSAF) exhibits a potent and broad antifungal activity with a novel mode of action. Increased production and reduced cost of raw materials are particularly important for the future production of HSAF, however, no report was involved in these studies. This study aimed to improve the production of HSAF with cheap raw materials through the medium optimization, which would lay the foundation for the application of HSAF in biological control.