Utilization of waste frying oil for rhamnolipid production by indigenous Pseudomonas aeruginosa: Improvement through co-substrate optimization

Conversion of fatty acids content of waste frying oils into value added product is better option to manage this waste. Use of waste frying oil for production of rhamnolipid by an indigenous P. aeruginosa and improvement of yield through optimization co-substrate (glucose) studied. Microbe isolated from frying oil condensate deposited on exhaust vent and further screened to utilize glucose with frying oil used in study. RSM (CCD) was used to optimize responses of rhamnolipid production, cell growth and specific production rate that influenced by independent variables frying oil (0 - 20 g/L), glucose (0 - 20 g/L) and ammonium nitrate (0-2.5 g/L). Co-substrate utilization showed effects on cell growth, quorum sensing and changed biosynthetic pathway to improve rhamnolipid production. RSM optimized the glucose (9.7 g/L) with frying oil for the highest effect of the cosubstrate with rhamnolipid yield 6.3 g/L (5.0 times), Q(Pmax) 0.4 h(-1) (9.5 times) and higher substrate diversion towards product (3.0 times) than towards the cell growth. Biosurfactant showed surface tension reduction to 30 mN/m at CMC 150 mg/L, emulsification indexes E-24 84 % and 62 % with vegetable (soybean) oil and kerosene respectively. Cost effective production of rhamnolipid is possible using waste frying oil substrate with optimization of sugar containing wastes (molasses, canneries waste etc.) in media.