Asian Journal of Microbiology, Biotechnology & Environmental Sciences Paper

Vol 19, Issue 4, 2017; Page No.(817-830)


Khaled E. El-Gayar


A total of three tap water and four commercial packaged water samples were randomly collected from Jazan district, KSA. The bacterial total count of all samples was calculated. Using biochemical tests and 16S rRNA gene sequencing, one bacterial isolate was identified as Bacillus subtilis. Antibiotic susceptibility test was performed using disc diffusion technique. Bacillus subtilis showed high resistance to Rifampicin only. Heavy metal sensitivity test of Bacillus subtilis was determined. Bacillus subtilis was resistant to Chromium and sensitive to Mercury, Cadmium, and Silver at minimum concentration (25mg/L). It was tolerant to Zinc, Cupper and Lead up to 100 mg/L. The biomass maximum yield from bacterial culture was the highest in the cultures containing 1% yeast extract. The optimum salinity for bacterial growth was at 0.5% NaCl. Also, Bacillus subtilis showed maximum growth at 37 oC and pH 7and it was tolerant up to 48 oC. Bacillus subtilis posed amylolytic and proteolytic with gelatinolytic activities. Protease activity was gradually increased with the increasing of incubation temperature of Bacillus subtilis growth up to 50 oC but the optimum temperature for amylase activity was at 37%. Optimal protease activity for Bacillus subtilis strain was increased at 20% skim milk. The maximum amylase activity was at 0.2% starch. The protease activity was increased with increasing of Calcium salt concentration up to 20 mg/L. However it was increased with increasing of Magnesium salt concentration up to 40 mg/L. Protease activity was slightly increased with addition of 80 mg/L from Manganese salt concentration. Amylase activity was increased with increasing of Calcium and Manganese salts concentrations up to 20 mg/L. However the optimum enzyme activity was increased with increasing of magnesium salt concentration up to 40 mg/L. Clear antifungal potentiality was reported by Bacillus subtilis strain against Curvularia lunata. The obtained result revealed that Bacillus subtilis has a noticeable antagonistic action in opposition to the tested pathogen.

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