An in vitro assessment on the efficacy of clay-based formulated cells of pseudomonas isolate UTAR EPA2 for petrol degradation

Problem statement: Application of free-cell forms is usually impractical to achieve satisfactory bioremediative effect because the microbes are encumbered by the biotic and abiotic stresses from the environment. Approach: In this study, a hydrocarbon-degrading bacterium (Pseudomonas isolate UTAR EPA2) was formulated with various combinations of formulative materials, comprising of clay-based carrier materials such as Bentonite (B) and Kaolin (K), enrichment materials such as Non-fat skimmed milk (N) and Sucrose (S) and a UV-protectant agent Para- aminobenzoic acid (P). Formulated cells were treated to sunlight exposure for 6 h to mimic the conditions in the environment prior to testing for their efficacy in degrading petrol, a mixed hydrocarbon substrate. Results: Cells in all formulations including free-cell suspension were able to degrade petrol with a relatively high degradation efficacy of more than 66% even after exposure to sunlight. Degradation efficacy was slightly higher for kaolin-based formulated cells compared to bentonite-based formulations, especially after exposure to sunlight, although their percentages of degradation were not statistically different. Nevertheless, kaolin-based formulations have very low viable cell count especially in formulations with P (KP, KNP, KSP, KNSP). This suggested that aside from viable cells, the physical properties of the clays could have also contributed to the degradation of petrol. Conclusion: For storage purposes and applications in the field, we suggest that the bacterium is formulated with bentonite-based formulations especially using Bentonite (B) clay singly, as relatively high percentage of petrol degradation and viable cell count was achieved with this formulation.