Screen, identification and fermentation optimization of an antifungal bacterium Z21

Abstract:

[Background] Many species of Bacillus with the merits of strong stress resistance and safety for human become a research hotspot in exploiting new active substances. [Objective] To isolate and screen antifungal bacteria and develop its active ingredients as a natural bio-antifungal agent of food. [Methods] These methods of plate culture, plate-confrontation and mycelia growth inhibition were used to isolate and screen antifungal bacteria from air and bamboo endophytic bacteria. Z21 was identified based on morphological, physiological, biochemical characteristics and 16S rRNA gene sequence. The growth conditions of Z21 were through orthogonal experiment. [Results] Z21 showed strong antifungal activity to 6 kinds of fungi. The 16S rRNA gene sequence of Z21 was consistent with that of Bacillus methylotrophicus CBMB205T, and the morphological characteristics and physiological and biochemical characteristics of Z21 were consistent with the CBMB205T strain. The optimum culture conditions for Z21 were 32 °C for 48 h with a medium of glucose 20.0 g/L, NaNO3 20.0 g/L and MgSO4 3.0 g/L. [Conclusion] The Z21 was identified as B. methylotrophicus, it showed strongly and stalely inhibitory activities against Aspergillus niger, Trichoderma koningii, Trichoderma viride, Rhizopus arrhizus, Mucor fragilis, and Penicillium ochrochloron. So it was an abroad-spectrum antifungal bacterium.