Optimization of biosurfactant production by Streptomyces isolated from Egyptian arid soil using Plackett-Burman design

摘要

Surfactants are amphipathic molecules which reduce surface tension, widely used in pharmaceutical, cosmetic and food industries. The current study aimed to isolate Streptomyces species from Egyptian arid soil, efficient in biosurfaclant production. Fifty isolates of Streptomyces were obtained from arid soil in Egypt. Primary screening, using lipase, drop collapse, parafilm M> and haemolysis tests, showed 37 isolates (74%) having biosurfaclant activity. Secondary screening resulted in 17 isolates based on their activities using emulsification index method. Isolate 5S was selected as the most efficient in biosurfaclant production, having emulsification index equal to 31.74%. Plackett-Burman design was adopted to evaluate the factors affecting biosurfaclant production. Among the tested nine variables of starch nitrate medium, treated molasses, peptone, Tween 80, incubation period and inoculum size were identified as significant factors affecting bio-surfactant production. Cultivation of isolate 5S inthe optimized medium elevated biosurfaclant production to 42.68% (according to emulsification index) from 31.74%, obtained in un-optimized medium.