Isolation and antifungal activity of a biosurfactant-producing bacterium

Abstract:

[Objective] The objective of this study was to examine the production of biosurfactant, taxonomic position and antifungal activity of the strain BS1. [Methods] Biosurfactant-producing bacterium was isolated by hemolytic activity assay on blood agar plates and hydrolyzing oil activity estimation on oil agar plates. Oil spreading method was used to assay surface activity. The strain BS1 was indentified according to morphological features, physiological and biochemical characteristics and 16s rDNA sequences of the strain. Antifungal activity was tested by dual-culture method and the inhibiting effect on the the mycelium growth, sporagium formation and spore germination. [Results] The strain BS1 of producing biosurfactant, isolated from the petroleum-polluted soil, was indentified as Pseudomonas sp.. The strain BS1, fermentation supernatant and the volatile compounds (VCs) exhibited inhibition activity on 12 kinds of plant pathogenic fungis. The strain BS1 and fermentation supernatant displayed significant inhibition to the Phytophthora sojae, the inhibitory rate was 65.31% and 95.93%, respectively. The fermentation supernatant of BS1 inhibited the growth of Phytophthora sojae by inhibiting mycelium growth, sporagium formation and spore germination, which had also remarkable inhibition even if it was diluted 20 times with pure water. VCs produced by strain BS1 had notable inhibiting effect against Sclerotinia sclerotiorum, and its inhibitory rate was 84.25%. [Conclusion] The strain BS1 can produce surfactant and has the potential biocontrol.