title: Evaluation of critical nutritional parameters and their significance in the production of rhamnolipid biosurfactants from Pseudomonas aeruginosa BS-161R.
abstract: Eleven biosurfactant producing bacteria were isolated from different petroleum-contaminated soil and sludge samples. Among these 11 isolates, two were identified as promising, as they reduced the surface tension of culture medium to values below 27 mN m(-1) . Besides biosurfactant production property, they exhibited good flocculating activity. Microbacterium sp. was identified as a new addition to the list of biosurfactant and bioflocculant-producers. Optimization of various conditions for rhamnolipid production was carried out for one of the promising isolate, Pseudomonas aeruginosa BS-161R. Bioglycerol (2.5%), as a cheap renewable carbon source, attained better rhamnolipid yield, while sodium nitrate appeared to be the preferable nitrogen source. The optimum carbon to nitrogen (C/N) and carbon to iron (C/Fe) ratios achieved were 15 and 28,350, respectively, which favored rhamnolipid production. Physical parameters like pH, temperature, and agitation speed also affected the production of rhamnolipids. Results from shake flask optimization indicated that the concentration of bioglycerol, sodium nitrate, and iron were the most significant factors affecting rhamnolipid production, which was supported by the results of central composite rotatable design. After optimization of the culture conditions, the production of rhamnolipids increased by ninefold from 0.369 to 3.312 g L(-1) .
authors.affiliation: Div. of Natural Products Chemistry, Chemical Biology Laboratory, CSIR-Indian Institute of Chemical Technology, Hyderabad, India. cgkumar1@rediffmail.com
authors.forename: Chityal Ganesh
authors.initials: CG
authors.lastname: Kumar
authors.forename: Suman Kumar
authors.initials: SK
authors.lastname: Mamidyala
authors.forename: Pombala
authors.initials: P
authors.lastname: Sujitha
authors.forename: Hemalatha
authors.initials: H
authors.lastname: Muluka
authors.forename: Surekha
authors.initials: S
authors.lastname: Akkenapally
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D001709:Biotechnology / Q000379:methods*; D002244:Carbon / Q000378:metabolism; D003470:Culture Media; D004269:DNA, Bacterial / Q000235:genetics; D005990:Glycerol / Q000378:metabolism; D006017:Glycolipids / Q000032:analysis / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D015999:Multivariate Analysis; D009584:Nitrogen / Q000378:metabolism; D010802:Phylogeny; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013500:Surface Tension; D013501:Surface-Active Agents / Q000032:analysis / Q000378:metabolism*
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D006017:Glycolipids; D012336:RNA, Ribosomal, 16S; D013501:Surface-Active Agents; C418382:rhamnolipid; D002244:Carbon; D007501:Iron; D009584:Nitrogen; D005990:Glycerol