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Kinetics and modeling of hexavalent chromium reduction in enterobacter cloacae

Kinetics of bacterial reduction of toxic hexavalent chromium (chromate: CrO42−) was investigated using batch and fedbatch cultures of Enterobacter cloacae strain HO1. In fedbatch cultures, the CrO42− feed was controlled on the basis of the rate of pH change. This control strategy has proven to be useful for avoiding toxic CrO42− overload. A simple mathematical model was developed to describe the bacterial process of CrO42− reduction. In this model, two types of bacterial cells were considered: induced, CrO42−‐resistant cells and uninduced, sensitive ones. Only resistant cells were assumed to be able to reduce CrO42−. These fundamental ideas were supported by the model predictions which well approximated all experimental data. In a simulation study, the model was also used to optimize fed‐batch cultures, instead of lengthy and expensive laboratory experiments. © 1993 John Wiley & Sons, Inc.