Bioremediation of Vegetable Oil Contaminated Soil with Two Microbial Isolates

Abstract

Vegetable oil spills are becoming frequent and are potentially more challenging than petroleum hydrocarbon spills. Microbial lipases occupy a place of prominence among biocatalysts and are often used for the remediation of vegetable oil spills. There is a need for extensive characterisation of lipase for the treatment of vegetable oil-polluted sites. This work was carried out to monitor the degradation pattern of vegetable oil. Two microbial isolates previously isolated from an oil mill in Ibadan, Nigeria were used for the bioremediation experiment. Soil samples (with some purposely contaminated with 2 different vegetable oils) collected from the Nursery section of the Microbiology department as well as soil samples from the oil mill were all subjected to varied treatment processes. Field bioremediation using the isolates was carried out for 12 weeks. The isolates were identified, and microbial load and residual oil weight were determined during the degradation period using standard methods. The two isolates were identified as Pseudomonas fluoresecens and Candida parapsilosis. The result of sterile soil samples with and without mixing option, from palm oil and palm kernel purposely contaminated soils for all the various treatments, showed a general increase in total viable counts from the 2nd week to the 12th week, however in the non-sterile counterpart there was a steady increase from the 2nd week to the 8th week and subsequently, a gradual decrease from the 10th to the 12th week. The residual oil weight in the sterile purposely palm oil-contaminated soil, treated with the consortium (POC) non-mixed gave a reduction of value from 0.335 g on day 0 to 0.13025 g by the 12th week. From the oil mill non-sterile, treated with (POC) non-mixed sample, the residual weight after 12 weeks of treatment was 0.0043 g from an initial weight of 0.01 g. The microorganisms Pseudomonas fluoresecens and Candida parapsilosis had the potential for the degradation of fatty waste. They could therefore be employed in the environmental cleanup of the vegetable oil spill sites.