Isolation and optimization of pure culture of bacillus subtilis, bacillus megaterium, bacillus pumilus - Collected from commercial shrimp ponds

Abstract

Commercial probiotics used for water quality management in shrimp farming often contain Bacillus spp. The aim of this study is to isolate Bacillus subtilis, Bacillus megaterium and Bacillus pumilus collected from shrimp ponds and natural waters in Xuyen Moc, Ba Ria Vung Tau province and optimize the conditions for their growth.

All three strains were successfully obtained from the collected water and sediment samples. Subsequently, 16S rRNA gene sequencing confirmed they are the strains of target. Shaking culture tubes resulted in significant higher growth rate of these bacteria than without shaking. As for pH, the highest growth was observed at pH 7 for all three strains. Inoculum size at the level of 100 ml served to be the best condition for all of three bacteria and the highest growth was obtained after 24 hours of incubation at 37oC.

Keywords: isolation, optimization, Bacillus subtilis, Bacillus megaterium,

Bacillus pumilus