Enhanced hexazinone degradation by a Bacillus species and Staphylococcus species isolated from pineapple and sugarcane cultivated soils in Kenya

Abstract

In this work, hexazinone-degrading bacterial strains from Kenyan tropical soils with long term application history were isolated and identified. Non-sterile soils from sugarcane and pineapple cultivated fields with over 15 years' hexazinone application history degraded 82.2% and 93.4% initially applied hexazinone under laboratory conditions after 146 days of incubation, respectively. In contrast, non-sterile soils without history of application degraded 48.8% and 36.8% of hexazinone after 146 days, respectively. From liquid culture tests, using soils with prior application history from sugarcane and pineapple cultivated soils, two hexazinone-degrading bacterial strains were isolated and identified as Staphylococcus gallinarum and Bacillus toyonensis and Bacillus thuringiensis, respectively. The pure isolates rapidly degraded hexazinone up to 38.4% and 53.2% of 50 mg/L in 46 days, respectively, with microbial hexazinone metabolite B previously reported detected. These bacterial strains from Kenyan soils have been identified for the first time as prospective hexazinone-degraders from pineapple and sugarcane-cultivated soils.