A Mathematical Model for End-Product Toxicity

摘要

Alcohol based biofuels,such as bio-butanol,have considerable potential to reduce the demand for petrochemical fuels.However,one of the main obstacles to the commercial development of biological based production processes of biofuels is end-product toxicity to the biocatalyst.We investigate the effect of end-product toxicity upon the steady-state production of a biofuel produced through the growth of microorganisms in a continuous flow bioreactor.The novelty of the model formulation is that the product is assumed to be toxic to the biomass.The increase in the per-capita decay rate due to the presence of the product is assumed to be proportional to the the concentration of the product.The steady-state solutions for the model are obtained,and their stability determined as a function of the residence time.These solutions are used to investigate how the maximum yield and the reactor productivity depend upon system parameters.Unlike systems which do not exhibit toxicity there is a value of the feed concentration which maximises the product yield.The maximum reactor productivity is shown to be a sharply decreasing function of both the feed concentration and the toxicity parameter.In conclusion,alternative reactor configurations are required to reduce the effects of highly toxic products.