Enzymatic hydrolysis of solid substrates: Critical notes and experimental guidelines for improvements

Optimization strategies of enzymatic reactions on solid substrates often suffer from unsystematic strategies and selection of unsuitable parameters. We present an efficient three-step guideline for optimization of enzymatic digestion processes taking the hydrolysis of cellulose by cellulases as an example. In the first step, intrinsic properties of the cellulases are addressed by the identification of optimal pH and temperature via design of experiments and subsequent evaluation. Process engineering parameters for the use of solid substrates greatly affecting the enzymatic reaction are further identified. These parameters are optimized in separate investigations and can be used for scale-up. The conclusive step contains the determination of product concentration with ongoing time, which can be performed in heterogeneous Michaelis-Menten approaches to achieve scientifically relevant data.