Optimal control of fed-batch reactor for enzymatic hydrolysis of lignocellulosic feedstocks

Lignocellulosic(LC) feedstock is one of the potential renewable sources for producing ethanol (second generation biofuel). However, technological bottlenecks and economic viability are of prime concern in producing ethanol from the LC feedstocks. In this context, to improve the process economics; one of the economically impacting process step in biochemical process route viz. enzymatic hydrolysis is optimized. In general fed-batch reactor is preferable option for enzymatic hydrolysis due to high productivities. The optimization of fed-batch operation generally involves finding the optimal substrate feeding profiles, with a view to optimize the performance index/ objective functional. With this scope, the kinetic model of enzymatic hydrolysis for LC feedstocks processing is considered from literature. Subsequently, the kinetic model parameters are used to develop a fed-batch reactor model for enzymatic hydrolysis process by associated mass balances. Optimal control has been implemented to determine the optimal time dependent profiles of substrate feed rate for fed-batch reactor to optimize the process performance. In this work, different objective functions such as maximizing concentration of glucose and, minimizing the batch time have been considered. The simulation results have provided the optimal operating policies to improve techno-economic feasibility of enzymatic hydrolysis operation for processing LC feedstock.