Author: Anaukwu Chikaodili Gladys
Department: Applied Biochemistry
Affiliation: Nnamdi Azikiwe University Awka

The use of biosurfactant produced by bacteria isolated from spent-oil polluted soil, in biodegradation of crude oil was investigated. Twenty-nine bacterial isolates were recovered and tested for biosurfactant production. Two potential surface-active producing bacteria were identified as Pseudomonas monteilii and Citrobacter murliniae. The influence of cultural conditions on biosurfactant production, based on emulsification index (E24), showed that 40% medium/fermenter volume ratio increased biosurfactant production in P.monteilii while 50% ratio improved production in C. murliniae. Maximum production of biosurfactant by P.monteilii was obtained with maltose at 1% concentration having E24 of 70%, while production by C. murliniae was enhanced by glucose at 2% concentration with E24 of 62.86%. Among the nitrogen sources studied, sodium nitrate was found to be the nitrogen of choice for P. monteilii and C. murliniae at 1% and 0.5% respectively. At a pH of 7.5, P. monteilii gave high yield of biosurfactant (E24 = 66.67%), while C. murliniae stimulated an increase at a pH of 8.0 (E24 = 63.33%). The effect of agitation speed revealed that biosurfactant production in P.monteilii and C. murliniae was optimal at 200rpm. The cell-free culture broths (CFCB) obtained from P. monteilii and C. murliniae grown on MSM were able to reduce surface tension of water from 72mN/m to ~34mN/m and ~42mN/m respectively.The crude biosurfactants had critical micelle concentrations (CMC) of 50mg/L and 60mg/L for P. monteilii and C. murliniae respectively. P. monteilii had the highest emulsification index (100%) with palm oil and least (43.33%) with groundnut oil. C. murliniae showed highest emulsification index (73.33%) with palm oil and least (33.33%) with petrol. Results on oil degradation showed that P. monteilii had 98% degradation when combined with biosurfactant and 43% degradation with Tween-80, while C. murliniae had 96% degradation with biosurfactant and 78% degradation with Tween-80.

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