The minimal enzyme cocktail concept for biomass processing

Efficient generation of a fermentable hydrolysate is a primary necessity in the utilization of fibrous plant biomass as a feedstock in bioethanol processes. Enzyme catalyzed hydrolysis of cellulose and heteroxylans in biomass feedstocks each require multiple enzyme activities to achieve degradation to fermentable monosaccharides. The minimal enzyme cocktail concept concerns identification of the minimal number, the minimal levels, and the optimal combination of the best performing key monoactive enzymatic activities to meet this requirement. Two major hypotheses lie behind this concept: 1. That the native multi-component profiles of crude “wild type” cellulolytic and/or xylan degrading enzyme preparations are not optimal for degradation of cellulose in pre-treated lignocellulosic biomass nor for degradation of heteroxylans in hemicellulose-rich product streams; 2. That it is possible to replace crude multienzyme preparations with designed combinations of the minimal number of required enzyme activities for biomass processing. This paper outlines the current strategies employed and the stage of development of minimal enzyme cocktails for enzymatic hydrolysis of cellulose and arabino-xylan in complex, genuine biomass substrates. The available data demonstrate the feasibility of the concept and illustrate the potential efficacy improvements obtainable by use of designed minimal enzyme cocktails for pre-treated lignocellulosic and hemicellulose-rich biomass substrates.