Modelling Cr(VI) reduction by pure bacterial cultures

Cr(VI) reduction data obtained with three bacterial species (Escherichia coli ATCC 33456, Bacillus sp., Pseudomonas fluorescens LB 300) were analyzed using an enzyme-based kinetic model. The model was developed by incorporating enzyme kinetics and a finite Cr(VI) reduction capacity to illustrate toxic effects of Cr(VI). The model was also used to analyze Cr(VI) reduction data taken from the literature for two other Cr(VI)-reducing species (Desulfovibrio vulgaris ATCC 29579, and Pseudomonas ambigua G-1). Although our different genera of bacteria were involved, the model was found to be capable of describing Cr(VI) reduction. The finite capacity indicates the maximum amount of Cr(VI) that a batch culture can reduce and it was explicitly demonstrated regardless of subsequent cell growth. The lost of Cr(VI) reduction capacity in bacterial cells may be attributed to the mutagenic and toxic effects of Cr(VI). The batch cultures reduced Cr(VI) at rates which decreased progressively with the amount of Cr(VI) reduced. Cr(VI) reduction ceased whenever the maximum capacity was reached.