Lab scale reactor for the kinetic assessment of biomass hydrolysis catalysed by cellulase

The effective hydrolysis of lignocellulosic biomass catalysed by cellulase cocktails is a crucial step of the biorefinery approach towards the production of fuels and chemicals from fermentable sugars. Enzymatic hydrolysis of biomass is a heterogeneous process involving cellulases as biocatalysts that can be inhibited by produced sugars (glucose and cellobiose). The heterogeneous process includes the enzyme interaction with biomass and the subsequent cellulose and hemicellulose enzymatic hydrolysis, it can be characterized by more or less complex techniques depending on the final purpose [1,2]. Process design asks for reliable tools for cellulase kinetics modelling that can be applied to different cellulase cocktails provided by the continuous research efforts aimed at the selection of more active and stable enzyme forms. Semimechanistic models can be adopted in process design in order to take into account the effect of external mass transfer, of enzyme and substrate (biomass) concentration as well as of product inhibition [3]. The present contribution reports on part of the study included in the research project Waste2Fuels funded in the framework of the European Horizon 2020 work programme. The aim is the development of an experimental procedure to assess kinetics of cellulase cocktails under reliable conditions not limited by the liquid-solid mass transfer rate. Preliminary results concern the design and set up of a lab scale batch reactor that is equipped with a packed column loaded with biomass granules and a stirred buffer tank. The liquid buffer, supplemented with the enzymes, was recirculated through the packed column and the tank so that the entire unit was operated as a Stirred Tank Reactor (STR). Liquid recirculation rate was varied to assess the minimum liquid superficial velocity that correspond to not limiting mass transfer rate between the liquid phase and the biomass granules in the packed column. Under the selected kinetic regime, further experiments will be carried out to assess cellulase kinetics in terms of dependence on enzyme and substrate concentration.