Optimization of culture conditions for promoting heat-stable antifungal factor production level in Lysobacter enzymogenes

Abstract

Heat-stable antifungal factor (HSAF) was firstly isolated from Lysobacter enzymogenes, it occupies inhibitory activities against a wide range of pathogens, but a low level of HSAF was obtained from L. enzymogenes cultured in 0.1 × tryptic soy broth (TSB) that does not satisfy HSAF application in a great deal in disease control. In this study, optimization of media components and environmental conditions were examined for improving the production of HSAF from L. enzymogenes OH11. The one factor at a time method was used to screen optimal nitrogen source, carbon source and inorganic salt. Then, the orthogonal matrix method was used to determine the optimal concentration of the media components and environmental factors. The results showed that the maximum level of HSAF (23361 mAU·s) was achieved when OH11 cultured in the media of 0.7% (w/v) soybean powder, 0.5% (w/v) glucose and 0.08% CaCl₂ at 200 rpm, 30°C for 60 h, which is much higher than that cultured in 0.1 × TSB. It provides a possibility for HSAF or L. enzymogenes utilization to plant disease biological control.

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