Abstract

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 kinetic assay, antioxidant activity began at early exponential growth phases; maximum activity was reached at the stationary phase. Scavenging effects on DPPH, the hydroxyl and superoxide radicals, Total antioxidant capacity (T-AOC) 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 the pH range of 2 to 12, temperature from 40°C to 121°C, as well as in some organic solvents. Thin layer chromatography assay by DPPH scavenging assay show two active spots with Rf values of 0.35 and 0.47 and both of them were ninhydrin positive.

Key words: Antioxidant activity, Bacillus simplex, thin layer chromatography (TLC), bacteria, sand soil biological crusts