Isolation, screening and growth optimization of antagonistic Bacillus subtilis MS21 from Thengapattanam estuary against plant fungal pathogens

Abstract

In the present work marine sediment samples were collected from Thengapattanam estuary on the south west coast of India for the isolation and screening of bacteria for biocidal potency. The density of the bacterial load in the sediment samples was ranged from 5.43x10 to 2.8x10 CFU/g. Screening of bacterial isolates for antagonistic activity revealed that the isolate MS21 had the highest zone of clearance among against all the 10 plant fungal pathogens tested. Among 10 fungal pathogens, the highest antagonistic activity was observed against Gleosporium gleosporioide (36mm) and the lowest against Colletotrichum lamella (11mm). The potential isolate was identified as Bacillus subtilis using biochemical methods and it was designated as Bacillus subtilis MS21. Effect of various physicochemical parameters on growth of B. subtilis MS21 showed that 36 hrs of incubation period, 150 rpm agitation, pH8.0, temperature-35C, salinity-1.0%, 2% sucrose as carbon source and 1% beef extract as nitrogen source were found to be the ideal conditions for maximum growth. Maximum growth of 1.92 OD was observed in mass scale culture with the optimized ideal conditions in the shake flask.