Studies on the Effects of Bioprocess Parameters and Kinetics of Rhamnolipid Production by P. aeruginosa NITT 6L

B. Vanavil, M. Perumalsamy and A. Seshagiri Rao

Abstract
Biosurfactants are gaining popularity in recent times due to lower toxicity, biodegradability, environmental compatibility and activity in extreme conditions. An air isolate was isolated previously for biosurfactant production in our laboratory, and characterized and named as P. aeruginosa NITT 6L. The biosurfactant thus produced was characterized to be surface-active rhamnolipid. This paper presents the study of the influence of various bioprocess parameters such as agitation, aeration and inoculum volume on rhamnolipid production by the isolate. Kinetics of rhamnolipid production in optimized media and process conditions were investigated. The rhamnolipid production was found to be increased after nitrogen depletion during stationary phase. The maximum rhamnolipid concentration of about 7.65 g L–1 was achieved after 96 h. Logistic model was found to be satisfactory in fitting the microbial growth. Emulsification activity of the crude rhamnolipid extract with different hydrocarbons was studied. The crude extract of rhamnolipid reduced the surface tension of water from 71.4 to 27.5 mN m–1, and CMC was about 11 mg L–1. Also, the usefulness of the extracted rhamnolipid produced under optimal conditions was investigated for remediation of crude oil contaminated soil. Soil washing with 0.3 % rhamnolipid removed about 71 % of crude oil present in sand samples within 24 h.

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Keywords
bioprocess, P. aeruginosa, rhamnolipid, kinetics, oil removal