Evaluation of a recycling bioreactor for biosurfactant production by Pseudomonas aeruginosa MR01 using soybean oil waste

BACKGROUND This study deals with the large‐scale production of biosurfactant from soybean oil soapstock by Pseudomonas aeruginosa MR01 . The production of biosurfactant was carried out in a newly designed bioreactor equipped with recycling flow under three operational conditions. Kinetic studies were conducted at both shake flask and 5‐L bioreactor scales during fermentation in a soapstock medium. Mathematical equations were developed to model the kinetic patterns at both scales. RESULT Statistical analyses demonstrated the goodness of fit, with regression r‐squared, R 2 , between 0.97and 0.99 for different models. Furthermore, biosurfactant concentration in the bioreactor including the recycling flow, which was switched on and off during a 6‐h period, reached 25.5 g L −1 ( Y P /S =0.9) which showed 41.5% and 21.5% growth compared with experiments conducted in a shake flask and a non‐recycling‐flow bioreactor, respectively. Moreover, the crude biosurfactant at a concentration of 24 mg L −1 was observed to have lowered the surface tension of double‐distilled water from 72 mN m −1 to 28.5 mN m −1 and displayed an emulsification index ( E24 ) of 63% against kerosene. CONCLUSION The results showed the recycling‐flow bioreactor to be a feasible model for further large‐scale studies of biosurfactants. © 2015 Society of Chemical Industry