Alkaline lipase production by Citrobacter freundii IIT-BT L139

Around 150 lipase producing bacterial isolates were screened from the local soils enriched with oil. Citrobacrer freundii IIT-BT L139, an isolated microbial strain, produced lipase that had high activity (8.8 U/ml) at pH 9.0 and 40 degrees C. The 16S rDNA phylogenetic studies showed that Citrobacter freundii belongs to the family Enterobacteriaceae and later confirmed by the microbial identification. Suitable C and N sources for lipase production were deduced to be starch and peptone-urea, respectively. In a controlled fermenter (1 L), the lipase activity was found to increase by 36% (12 Uml(-1)). The variation of lipase activity, pH and dissolved oxygen (DO) during growth of the organism in the controlled batch fermenter were monitored. The rheological characteristics of the fermentation broth indicated that it behaved like a Newtonian fluid throughout the fermentation. The fermentation time was comparatively short (60 h). The lipase was also found to be substantially resistant to common detergents. This lipase was, thus, characterized as alkaline, thermostable and solvent stable, which was essentially desirable in pharmaceutical, detergent and other industrial applications or production.