Screening of biosurfactant producing bacteria and optimization of
production process
Janpen Islam, M.Sc. Student in Biotech., PSU.
Aran H-Kittikun, Asst. Prof., D. of Industrial Biotech., F. of Agro-Industry, PSU.
Yaowaluk Dissara, Assoc. Prof., D. of Microbiology, F. of Science, PSU.
Corresponding e-mail : haran@ratree.psu.ac.th
Grant : Graduate school, PSU.
Presented : The 12th Annual Meeting of the Thai Society for Biotechnology "Biotechnology :
Impacts & Trends" Kanchanaburi, Thailand, 1-3 Novermber, 2000
Key words : biosurfactant, marine bacteria
During screening for biosurfactant producing, one hundred and twenty two marine bacterial strains were isolated from soil and seawater contaminated with petroleum wastes and enriched in (g/l) : bacto peptone, 5; yeast extract, 1 : NaCl, 19.45; MgCl2, 5.9; Na2SO4, 3.24; CaCl2, 1.8; C6H5FeO7.
H2O, 0.1; KCl, 0.55; CHNaO3, 0.16; KBr, 0.08; SrCl2.6H2O, 0.034; H3BO3, 0.022; NaF, 0.0024; NH4NO3, 0.0016 and Na2HPO4, 0.008. The initial pH was 7.2 and the culture temperature was 30oC. Haemolysis was used as a selection criterion for the primary isolation of biosurfactant-producing bacteria. Thirty-nine strains had haemolytic activity. Only eight strains, all of them were gram-nega-tive bacteria, were positive for weathered oil degrading capability. Later, biosurfactant production
was detected by emulsifying capacity and oil displacement test. Two strains (PA6 and S7) showed
high emulsifying capacity (0.47% and 0.51%) and oil displacement test (0.20 cm2 and 0.28 cm2).
When the organisms were cultivated in a defined marine broth (palm oil as a carbon source) for 3 days on rotary shaker (200 rpm) at 30oC, the production of the biosurfactant by PA6 and S7 was growth-associated. When palm oil was used as a carbon source both PA6 and S7, gave higher emulsifying capacity (0.87% and 1.85%) and oil displacement test (0.64 cm2 and 1.33 cm2) than when hexadecane, glucose or sucrose as a carbon source.
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