Bioconversion of sodium dodecyl sulphate to rhamnolipids by transformed Escherichia coli DH5α cells-a novel strategy for rhamnolipid synthesis.

Abstract

Biological synthesis of rhamnolipids from SDS by Pseudomonas aeruginosa S15 is found to be a cost effective mode of rhamnolipid synthesis. This study aimed to attempt rhamnolipid synthesis by transformant Escherichia coli DH5α cells. Molecular analysis by curing experiments revealed that the properties of SDS based rhamnolipid synthesis were plasmid borne. Transformation of 10 kb plasmid to E. coli DH5α cells conferred rhamnolipid synthetic ability to transformant. Various genetic elements involved in SDS based rhamnolipid synthesis were analyzed using PCR based and restriction digestion based approaches. PCR amplification using primers specific for sdsA gene encoding alkylsulfatases yielded two significant amplicons viz, 1·2 kb fragment and 422 bp fragment, coding for putative dehydratase and ABC transporter respectively. Amplicon of sdsB gene lacked ability of SDS degradation and rhamnolipid synthesis. Rhamnolipid biosynthesis by transformant E. coli DH5α containing the whole of the 10 kb plasmid, was optimized to yield of 3·38 g l(-1) in 5 days of incubation. Plasmid encoded rhamnolipid synthesis from recombinant E. coli cells is novel and could serve as yet another promising approach among various steps adopted for safe and effective rhamnolipid synthesis. SDS based rhamnolipid synthesis by S15 attained a high substrate (SDS) to product (Rhamnolipid) conversion ratio. However, the use of Pseudomonas strains is always discouraged as they are opportunistic pathogens and could sometimes turn infectious. Thus, transformation of genetic elements coding SDS based rhamnolipid synthesis to nonpathogenic strains could be promising.