S7: Application of new chromatography methods to improve both hydrolysis of lignocellulosic feedstock and growth of yeasts thereon

The feedstock for 2^nd generation biofuel is lignocellulosic biomass, such as wheat straw, bagasse or corn stover. For yeasts to grow on this feedstock, pretreatment and hydrolysis steps are needed to release the fermentable sugars into the lignocellulosic biomass hydrolysate. The composition of different hydrolysates can be quite variable, due to the type of initial biomass used and also the choice for the pretreatment and hydrolysis methods. The final growth performance of different yeasts on such hydrolysates will be determined partly by strain characteristics, but mainly by the exact composition of the hydrolysate, i.e. the concentrations of inhibitory components.

In this study, methods were developed to determine the composition of various hydrolysates, generated from diverse biomass types and by different pretreatment and hydrolysis methods. In particular, an HPAEC-MS method was found suitable to identify the limiting and interfering factors to the activities of fungal enzyme cocktails used in the hydrolysis step. The results of this analysis allow targeted optimization of these cocktails. Other GC-methods were optimized for analysis of the more apolar inhibitory compounds. Detected concentrations were correlated to the growth performance of S. cerevisiae on multiple hydrolysates, as determined both in a Bioscreen C Analyzer and in fermentors.

The results show that our approaches are effective for evaluating and selecting the most suitable hydrolysate for a specific production purpose. The developed analysis methods have potential to enhance the enzymatic hydrolysis efficiency in the hydrolysates, and enable the systematic study on the hydrolysate inhibitory effects.