XJ-25, a strain with strong antioxidant activity was isolated from sand biological soil crusts in Gurban Tonggut Desert, Xinjiang, China. Strain XJ-25 is closely related to Bacillus simplex through the 16s rDNA sequencing combined with morphological, physiological and biochemical analysis. The medium for optimal antioxidant activity was NB with 1.5 g/Lglucose. Based on the kinetic assay, antioxidant activity began at early exponential growth phases; maximum activity was reached at the stationary phase. Scavenging effects on 2, 2-Diphenyl-1-picrylhydrazyl (DPPH), the hydroxyl and superoxide radicals, T-AOC capacity and protection against lipid damage were evaluated. The main antioxidant compounds were in the extracellular secreted supernatant of XJ-25. The active compounds were very stable at a pH range of 2 to 12, and temperature from 40 to 121°C, as well as in some organic solvents. Thin layer chromatography assay by DPPH scavenging assay showed two active spots with a Rf values of 0.35 and 0.47, and both of them were ninhydrin positive.
Key words: Antioxidant activity, Bacillus simplex, TLC, bacteria, sand soil biological crusts.
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