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
Highlights
It is well known that free radicals can damage DNA, proteins, lipids and carbohydrates within human tissues and cause many diseases, such as cancer, aging, diabetes (Baskar et al, 2004; Meghashri et al, 2010, Halliwell, 1991)
Cell growth was monitored by optical density measurement at 600 nm, and antioxidant activity was tested by DPPH assay
The mixture was stored at −20°C for 2 h followed by centrifugation at 12,000 rpm for 15 min at 4°C; both soluble and insoluble fractions were evaporated to dryness under speed-vacuum, suspended in distilled water, and antioxidant activity was tested by DPPH scavenging assay
Summary
XJ-25, a strain with strong antioxidant activity was isolated from sand biological soil crusts in Gurban Tonggut Desert, Xinjiang, China. The medium for optimal antioxidant activity was NB with 1.5 g/L glucose. 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
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