Metal tolerance and organic compound utilization of Bacillus species originated from wastewater

Abstract

Wastewater management has been one of the significant environmental concerns in the recent years. Organic material and heavy metal residues are among the contaminants of concern in wastewater and are spreading throughout the world along with the industrial progress. The use of microbes for the pollutant removal was a favourable alternative to conventional techniques. The aims of this study was (i) to identify bacterium JA based on 16S rRNA analysis, (ii) investigate the degree of bacterium JA tolerance towards various heavy metals (cobalt, copper, zinc, manganese and aluminium) and (iii) screen the ability of bacterium JA to utilize several selected compounds (glucose, glycerol, benzene, kerosene, sulfanilic acid and casamino acid) as the sole carbon and/or nitrogen source. Based on 16S rRNA analysis results, this bacterial strain was identified as Bacillus sp. In the heavy metals tolerance experiments, the maximum tolerance concentration of CuCl, ZnSO4, CoSO4 and AlK(SO4)2 in Bacillus sp. was 100mg/L, 100mg/L, 40mg/L and 500mg/L, respectively. In medium containing 100 mg/L of heavy metals (CuCl, ZnSO4, CoSO4, MnCl2, and AlK(SO4)2), the growth rate (µ) of Bacillus sp. was 0.497 h-1, 0.529h-1, 0.093h-1, 0.138 h-1, and 0.303 h-1 respectively, which clearly showed that cobalt had the highest growth inhibitory effect to Bacillus sp. From the carbon utilization tests, glucose and glycerol were the preferred growth substrates, where glycerol was observed to give the highest absorbance value (OD600=0.456) at 48 hours of incubation. No observable growth was seen when kerosene or benzene was supplied as the sole carbon source. Both sulfanilic acid (SA) and casamino acid (CA) were found independently to be used as sole nitrogen source, with CA was found to be a better source for the purpose of promoting the growth of Bacillus sp. No significant growth was observed when CA and SA were provided as carbon or carbon and nitrogen source.