Improvement in Production of Rhamnolipids Using Fried Oil with Hydrophilic Co-substrate by Indigenous Pseudomonas aeruginosa NJ2 and Characterizations.

Commercialization of biosurfactant remained a challenge due to lack of structural variation and economical process using low-cost materials and low productivity. Improvement in production of biosurfactant using fried oil with hydrophilic co-substrate by an indigenous strain was studied. Microbe isolated from exhaust chimney condensate was screened for utilization of mixed carbon source and then identified as Pseudomonas aeruginosa NJ2 by 16S rDNA gene sequence. FTIR, HPLC, and NMR analyses confirmed that biosurfactant was rhamnolipids. Batch fermentation using mixed substrates improved the cell growth yield to 1.48 g/L (2.34 times) and product yield to 4.28 g/L (3.4 times) with maximum specific growth rate 0.1 h-1 (two times) and specific production rate 0.5 h-1 (13 times) due to higher cell density and direct synthesis of lipid and rhamnose moieties through central metabolic pathways of the two substrates. Increase in carrying capacity and coefficient value (two times) of logistic equation confirmed the significance of mixed substrates. The biosurfactant showed excellent surface active and thermo-chemical stability properties. Economical production of biosurfactant with high yield and productivity could be possible by isolation of mixed carbon source utilizing strain and optimization of waste substrates from oil/soapstock and sugar/corn syrup industries in media.