Abstract:[Background] Biosurfactants produced by microorganisms have many characteristics, such as low toxicity, high efficiency and biodegradability, which can alleviate the environmental problems caused by chemical surfactants. Therefore, the screening of high-yielding and safe biosurfactant- producing strains has attracted more attention. [Objective] To screen biosurfactant-producing strains for medicine and food use from pickled vegetable. [Methods] A biosurfactant-producing strain obtained from pickled vegetables by the method of drop collapse and oil displaced circle, and this strain was identified by morphological observation, physiological and biochemical identification, rDNA ITS sequence analysis. The composition and functional properties of biosurfactants were identified and determined by the method of droplet collapse diameter, emulsification activity and chemical analysis.[Results] A biosurfactant-producing strain, Pichia manshurica YM-7, was screened from household pickled vegetables in Dianjiang District, Chongqing. The biosurfactant increased the droplet collapse diameter by 27.5%, and decreased surface tension of phosphate buffered saline by 49.21% (from 71.87 mN/m to 36.50 mN/m). The emulsification index of the biosurfactant extracts reached 63.0% after being mixed with vegetable oil in equal proportions at 8 days (the control droped to 0 after being placed for 6 days). [Conclusion] P. manshurica YM-7, an excellent biosurfactant-producing strain, was successfully screened from the pickled vegetable, and its biosurfactant has good emulsifying properties for certain application prospect in food, medicine and cosmetics industy.
