Model of bioconversion of cholesterol in cloud point system

摘要

Bioconversion of cholesterol to androst-l,4-diene-3,17-dione (ADD) and androst-4-ene-3,17-dione (4-AD) in cloud point system (CPS) was studied.A mathematical model was presented based on the mass transfer rate and microbial growth rate.The calculations for cell concentration,substrate concentration,and product concentration as functions of time were made.Sensitive analysis of model was made.Some parameters,such as substrate concentration,mass transfer coefficient,and maximum product inhibition concentration,indicated that the maximum product concentration is the most significant parameter in batch process.The prediction was validated by adjusting substrate concentration,stirring speed,and surfactant concentration.It showed the batch process of cholesterol bioconversion in CPS was controlled by inhibition of product.Adjusting surfactant concentration can diminish inhibition of product and increase final product concentration.The results also indicated that CPS can increase the substrate concentration of aqueous phase in batch process.