Yeast Extract as the Most Preferable Substrate for Optimized Biosurfactant Production by rhlB Gene Positive Pseudomonas putida SOL-10 Isolate

Abstract

Oil contaminated sites are enriched source of microorganisms that produce a variety of surface active amphiphilic compounds known as biosurfactants. Pseudomonas putida SOL-10 strain isolated from oil contaminated soil of Fimkassar oil field, Chakwal, Pakistan, was identified by standard morphological, biochemical and 16S rRNA sequence analysis methods. SOL-10 strain was initially screened for biosurfactant production using oil spreading test and then manifestation of rhlB (rhamnolipid) gene was confirmed by PCR using gene-specific primers. Maximum biosurfactant production in terms of surface tension (29.9 mN m-1) and emulsification index (E24, 73.45%), was achieved when the strain was grown in MSM supplemented with yeast extract (1.5-2 %, w/v) and urea (0.1 %, w/v) as carbon and nitrogen sources, respectively, and the physical parameters were adjusted at pH 7.0, temperature 30°C, 150 rpm agitation speed. The biosurfactant emulsified various hydrocarbons tested, being more effective against xylene and kerosene (85.19% and 70.59%, respectively). The crude biosurfactant also showed stability at a wide range of temperature (25-80°C), pH (1-9) and salt concentration (1-5%, w/v). The stability and hydrocarbon emulsifying potential of the biosurfactant indicated its possible use as decent contender for future environmental applications like biodegradation and bioremediation of organic pollutants.