Strain improvement for the production of antioxidant activity from Bacillus sp. by induced stress

Abstract

In the present study, water samples were collected from different beaches in Chennai such as Marina beach, Elliott beach, VGP Golden beach and Kovalam beach to evaluate the best source for antioxidants. The bacteria were isolated on Starch Casein Agar media and screened for the antimicrobial activity. Among 11 isolates, 5 isolates showed antimicrobial potential which were further evaluated for the DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity. Among 5 isolates, one sample showed significant DPPH scavenging activity with half minimal inhibitory concentration of (IC50)344.754µg/mL. The maximum antioxidant production was observed at pH 7 and at temperature of 37ºC with an IC50 of 188.66µg/mL and 293.76µg/mL respectively. The potent antioxidant producing strain was subjected for mutagenesis. In physical mutagenesis, the organism exposed for UV light for 25 minutes showed maximum antioxidant production with an IC50 of 133.55µg/mL. This mutant strain was then subjected for chemical mutagenesis with the addition of different concentrations of Ethidium bromide such as 10µL, 20µL, 30µL, 40µL and 50µL. The mutant strain obtained with the addition of 20µL Ethidium bromide (EtBr) showed significant antioxidant activity with an IC50 of 325.4µg/mL. The sample was purified by solvent extraction method and was evaluated for antioxidant production. The analyte was subjected to HPLC (High Performance Liquid Chromatography) analysis to avince the presence of antioxidants. The ethyl acetate extract showed the total phenolic content of 0.892 mg GAE/g of dry extract. It also showed the total flavonoid content of 0.522mg RE/g of dry extract.