Kinetic analysis and modeling of enzymatic hydrolysis and SSF

In the current work, a model for enzymatic hydrolysis and SSF has been reviewed and modified. Parameters referring to the enzymatic hydrolysis were estimated against new experimental data by using a non-linear least square regression tool in Matlab (MathWorks Inc.). To enable modeling of different substrates a new parameter accounting for different substrates susceptibility to enzymatic hydrolysis was added to the model. Softwood, sugar cane bagasse and Avicel were studied. Sugar cane bagasse was easiest to hydrolyze and Avicel the most difficult. The initial hydrolysis rate of softwood was about 60 % of that of bagasse. The model includes features such as end-product inhibition from cellobiose and glucose, enzyme deactivation, β-glucosidase adsorption to lignin, and the new substrate parameter. To simulate SSF the model was supplemented with simple microbial expressions, using fixed specific glucose uptake rate, yield coefficients, zero cell growth and an exponential cell death. The validity of the model was tested against experimental data differing from the experimental data used to estimate the parameters. The enzymatic hydrolysis simulations gave a deviation of about 10 % of the experimental glucose value. Similarly, the simulated SSF experiments gave a deviation of about 5 % of the experimental ethanol value. The result of the current work showed that modeling of enzymatic hydrolysis and SSF can be performed successfully using a rather complex model for enzymatic hydrolysis and a simple model for the fermentation.