5-65: The Effects of High Solids Conditions on Specific Enzymatic Activities Involved in the Saccharification of Lignocellulosic Biomass

Increasing political and economic pressures worldwide have spawned growing interest in recent years towards bringing the production of lignocellulose based fuels to the industrial scale. While research in this field has progressed greatly over the past thirty years, there are still a few fundamental problems that have so far remained unresolved and will prove crucial to the economic viability of lignocellulosic conversions. One of these is related to running the enzymatic saccharification/fermentation processes at high levels of dry solids (~ 20% dry matter) which is necessar for a cost effective process. To date a number of studies have reported depressed conversions with increasing solids concentrations compared to the levels typically used for bench scale studies (usually less than < 5 % dry matter). While a handful of studies have begun to reveal potential causes of this phenomenon, most often the studies are conducted using commercial cellulase preparations which are composed of a significant number of different enzyme activities and individual proteins. In recent studies we have attempted to determine if this effect is consistent across all enzyme activity types or if the adverse phenomenon can be isolated to certain groups of enzymes. We have investigated these high solids conditions with respect to a range of different commercial enzyme preparations in addition to a handful of purified enzymes representing activities that are known to be crucial to the overall conversions process. We believe that work of this nature will provide valuable insight to researchers investigating possible mechanisms behind this detrimental phenomenon.