Functional Bacillus Species in Camellia Seed Shell Compost

  Objective   Bacillus spp that contribute to the fermentation of Camellia oleifera seed shells were isolated for effective composting of the waste material.

  Method   The microbial community in natural camellia seed shell compost found in Guangxi was studied using the high-throughput sequencing technology. Suitable culture medium to foster the growth of richly diverse Bacillus spp from the compost was selected. Flora isolation by dilution with a streaking plate method followed. The hydrolase activities of the isolates were determined by using the hydrolysis circle method and enzyme activity analysis, the species identified by a 16S rDNA analysis, and the phylogeny constructed by MEGAX. The content of humic acid in the compost was measured by a potassium dichromate method.

  Result   Bacillaceae was the dominant family in the compost. It accounted for 55.58% of all isolated flora. Among the 15 Bacillus isolates, 6 exhibited activities of amylase, cellulase, and protease, one of amylase and cellulase, and 2 of protease or protease. Strain YX11 showed a protease activity of 27.07±3.28 U·mL⁻¹, an amylase activity of 123.97±3.19 U·mL⁻¹, and a cellulase activity of 15.75±0.23 U·mL⁻¹. In the presence of numerous Bacillus spp that secreted varieties of hydrolases, formation of humic acid in the compost was enhanced.

  Conclusion   Some of the isolated strains, such as B. cereus YX02 and B. flexus FYF01, might warrant further investigation to develop microbial inoculants for efficient composting camellia seed shells.