THOMAS HAHN, FABIAN HAITZ, SUSANNE ZIBEK*
*Corresponding author
Fraunhofer Institute for Interfacial Engineering and Biotechnology,
Nobelstraße 12, 70569 Stuttgart, Germany

Abstract

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.

RELEVANT PARAMETERS FOR CELLULOSE HYDROLYSIS
Enzymatic solid substrate hydrolysis is, due to increased utilization of renewable resources, a major economic factor in biotechnology. Pretreatment, purification and succeeding enzymatic hydrolysis of the solid substrates are of great scientific and economic interest. But there are still many challenges to face including the minimization of enzyme amount which represents a large cost factor, for example in cellulose hydrolysis (1). Optimization of hydrolysis was often carried out software-assisted by using many parameters with unsuitable boundary conditions resulting in non-expressive values. The present manuscript addresses the optimization of a solid substrate hydrolysis in a three-step procedure. Simultaneously we focus on common mistakes performed and provide facts that attention should be paid on. This is elucidated using the example of cellulose hydrolysis.
On the one hand, enzyme performance can be improved by outside or extrinsic ascendancies which in general increase the accessible surface of the solid substrate. To improve these extrinsic conditions ultrasound and ...