Tolerance and reduction of Cr(VI) by Bacillus amyloliquefaciens, B. thuringiensis and Paenibacillus sp., isolated from Pasto River

The accumulation of heavy metals such as Cr(VI) in the environment is a growing problem; however, the isolation of the bacteria present in these contaminated sources can provide an alternative for their treatment. In this sense, this research evaluated in vitro the percentage reduction of Cr(VI) and the effect of three concentrations (25, 60, and 100 mg/L of Cr(VI)) on the growth of bacterial isolates E4M3 Bacillus amyloliquefaciens [MK561611], E4M15 Bacillus thuringiensis [MK561610], and Paenibacillus sp. [MK561612]. Statistical analysis determined that 59% of the variation in growth is attributed to the interaction of bacteria and concentration (P <0.05; η2 = 0.59). Likewise, statistically significant differences were observed between bacteria concerning the percentage of reduction of Cr(VI) (P <0.05; η2 = 0.98). The data found on the population density and the percentage of reduction coupled with mathematical approximations are related to the intrinsic metabolic conditions of the bacteria and the selective pressure conditions of the environment where they are found.