Monday, May 4, 2009
5-50
The use of calorimetry to monitor inhibition during biomass hydrolysis
Christina Bohlin1, Kim Borch2, and Peter Westh1. (1) Roskilde University, Universitetsvej 1, Roskilde, Denmark, (2) Novozymes, Krogshoejvej 36, Bagsvaerd, Denmark
Enzymatic hydrolysis of lignocellulosic biomass is a complex process due to insoluble substrates, synergy effects between different enzymes and adsorption/inhibition of non-cellulosic components such as lignin or components derived from lignin during pretreatment. This complex process is hard to analyze and to address this problem the enzymatic activity have been monitored through the heat produced during hydrolysis using calorimetry, rather than the disappearance of substrate or the formation of products. With this technique it is possible to get real-time information of the enzymatic activity at high resolution in complex mixtures of lignocellulosic biomass containing non dissolved cellulose and lignin as well as non reacting components. This has previously been hard to obtain with other assay techniques. In this study the effect of lignin inhibition has been studied by titration with inhibitors to reacting mixtures of cellulose and cellulases and titration with cellulases into a mixture of inhibitors and cellulose. Changes in the heat produced as a result of addition of inhibitory compounds were there after evaluated. The inhibitors were both dissolvable and non-dissolvable lignin model compounds as well dissolvable and non-dissolvable ligniceous residues. Using this system it has been possible to compare the role of different functional groups as well as the role of total amount of different functional groups. Other factors that might influence the hydrolysis are high concentrations of sugars such as xylose and arabinose and a high ionic strength, which both are present after pretreatment of corn stover. These concerns were therefore also studied.