Optimization of the saccharification of sugar beet pulp for application to commercial biofuel production

The sugar beet pulp (SBP) saccharification reaction was examined in order to increase yield and cost-efficiency for application towards commercial biofuel production. A combination of commercial and in-house engineered enzymes targeted the pectin, hemicellulose and cellulose fractions of the SBP for saccharification. Reaction parameters were analyzed to improve the process including saccharification kinetics as well as limiters and inhibitors of the reaction. Exhaustion of enzymes and/or substrate as well as inhibition by acidification or glucose production were investigated as possible reaction limiters. The reaction showed a complex dependence upon substrate and enzyme concentration.  Further it was determined that the reaction is self-buffering and that added buffering is not required to optimize the reaction. Although glucose was found to inhibit the reaction, the glucose concentrations produced under our reaction conditions did not rise to the level where they would be inhibitory.   However, with additional substrate or more efficient saccharification, glucose inhibition would likely become an important consideration.  A protease pretreatment of SBP did not enhance saccharification. The optimized reaction converted 66% of SBP polysaccharides to soluble sugar in under 24 hours at 55^o C.