Enhancement of microbial degradation of crude oil polluted soil using Mexican sunflower (Tithonia diversifolia) and wild groundnut (Calapogonium mucunoides)

Abstract

This study was driven by the quest for a cheaper and safer means of enhancing crude oil hydrocarbon degradation in the soil. Soil samples (0 to 20 cm) were polluted with crude oil at 300 ml, mixed thoroughly and allowed to stand for fourteen days. Thereafter, the agro-wastes: “Calapogonium mucunoides (CM) and Tithonia diversifolia” (TD), were applied using the following amendment levels: pristine control (0 g), crude oil control (0 g), 100 g CM, 150 g CM, 200 g CM, 100 g TD, 150 g TD, 200 g TD, 100 g CM + 100 g TD, 150 g CM + 150 g TD and 200 g CM + 200 g TD. The amended and unamended soils were thoroughly mixed and allowed to stand for 42 days. Microbial analysis was conducted for total heterotrophic bacteria and fungi, crude oil utilizing bacteria and fungi and total hydrocarbon contents. The microbial isolates identified were as follows: Bacillus anthrax, Pseudomonas aeruginosa, Micrococcus luteus, Acinetobacter sp., Achromobacter sp. and Actinomyces sp. as bacterial isolates. Fungi isolates identified were: Aspergillus niger, Mucor indicus, Rhizopus sp. and Penicillium giabrum. Among the various amended groups, 100 g TD had the highest bacterial count of 9.92 × 10⁷ CFUg^-1, 200 g CM had a highest bacterial count of 2.25 × 10⁸ CFUg^-1, 200 g TD had the highest fungal count of 9.62 × 10⁶ CFUg^-1 and 200 g CM had the highest count of 8.46 × 10⁶ CFUg^-1. However the combined amendment groups enhanced the microbial proliferation at 200 g CM + 200 g TD with highest bacterial count of 2.25 × 10⁸ CFUg^-1 and 150 g CM + 150 g TD with highest fungal count of 8.83 × 10⁶ CFUg^-1. The result showed that C. mucunoides and T. diversifolia are effective in the enhancement of microbial degradation of crude oil-polluted soil.

Keywords: Degradation, crude oil, soil, microbial, polluted.