Anaerobic enrichment of <i>Bacillus</i> alkylbenzene remedial consortia from waste biomass melanoid sources

Abstract

<abstract> <p>Bioremediation of alkylbenzenes, including toluene, ethylbenzene and xylenes, was performed using fermentable aromatic sources and electron mediators by <italic>Bacillus cereus</italic> 301 in a limited oxygen state. The fermentation of small fermentable aromatic melanoids from cow manure as soluble humus hydrolysates or sugarcane molasses as saccharine, glucose and limited basal medium was compared. Thus, an evaluation model of exponential decline against a control was incorporated for interpretation of remedial data. The significance of the present strategy for constructing multivariant effects of electron donors could be objectively judged by pattern comparison with the short-term data analyzed. Thus, grafted aromatics as methyl- or ethylbenzene require much more microbial reaction time, even with mixed aromatic donors or stronger electron donors such as methanol in the original reduced medium, as indicated in the scatter chart. However, completion of the remedial time was needed by the kinetic simulation, and even low, smooth data were expressed. Among the exponential decay curves indicated, the carbon sources in the mix were favorably expressed. The smooth pattern indicated that fermentations with glucose and molasses showed lower remedial activity than melanoids or the indole series. The vigor increase was better for melanoid carbon in the initial fermentation of 24 h, while molasses increased later at 72 h and was more quenched by amending indole acetic acid (IAA) or indole expression. The molecular interaction of the electron mediator indole acetic acid in most trials indicated a quenched effect on toluene and ethylbenzene degradation, even when mixed with the original reducing medium, but expressed better with molasses in both kinetic simulations and growth effects. Thus, combining electron mediators such as IAA for <italic>Bacillus</italic> may offer a new degradation route for the metabolite alkylbenzene, which is worth further exploration for environmental aromatic waste remediation and combined restoration strategies.</p> </abstract>