Mutagenesis of Bacillus subtilis isolated from green waste compost by atmospheric and room temperature plasma treatment and its fermentation conditions

Abstract:

[Background] High-efficiency composting agents, especially fungi, have become a research hotspot for improving the efficiency of green waste compost. Due to the disadvantaged of fungi application such as its sensitivity to oxygen and substrate, the role of bacteria in composting process has gradually been studied. Bacillus subtilis (B. subtilis) BL03 was screened from the composting process of green waste using CMC-Na as substrate in our laboratory. The BL03 strain with good cellulose decomposition ability could improve the speed of cellulose degradation and humus synthesis in the green waste composting. [Objective] To further improve the cellulase activity of BL03. [Methods] The atmospheric pressure room temperature plasma (ARTP) was used to mutate the bacteria. Three rounds of screening were carried out via measuring the diameter of the hydrolyzed transparent circle on CMC-Congo red solid medium and detecting the activity of cellulase after liquid fermentation. The genetic stability of the mutant was measured after 10-generations culturing. The optimum growth temperature and initial pH of medium for mutant fermentation were determined by setting gradient temperature and pH culture. Orthogonal design was adopted to determine the industrial raw materials for the fermentation of the mutants. [Results] Two mutant strains, of which the enzyme activity increased by 69% and 72% respectively, were obtained. Also, the cellulase activity of the two mutants were stable after 10 generations culturing. The optimum culture temperature for the highest cellulase activity mutant, BLA3890, was 37 °C, and the initial pH of the medium was 5.0?6.5. An economical fermentation medium was obtained from this study. [Conclusion] BLA1973 and BLA3890, which obtained from Bacillus subtilis BL03 mutated by ARTP, are valuable in composting process of green waste or other cellulose degradation applications and need further research.