6-10: Media Requirements for for Aerobic Cultivation of Saccharomyces cerevisiae TMB 3400-F30-3 on Softwood Hydrolysate

The purpose of this study was to develop a low-cost industrial nutrient medium for the aerobic cultivation of a hydrolyzate-adapted Saccharomyces cerevisiae TMB3400-FT30-3.  This xylose-utilising yeast is a promising ethanologen for converting lignocellulosic biomass sugars to ethanol.  Dilute acid pretreated softwood hydrolyzate is a readily available and economic option for a carbon source for cell growth in the fermentation seed tank and has the added advantage of contributing to cell adaptation before the fermentation.  The focus of the work was to determine the minimal level of externally-supplied media supplementation in the form of beet molasses and nitrogen in the form of ammonium sulfate that will still result in near-maximal biomass yields during fed-batch aerobic growth.   The experimental work showed that it is possible to supply only 10 % of the sugars in the form of beet molasses (or 21 g/L of concentrated molasses) without any significant reduction of the biomass yield from its near maximum value of 0.45 g biomass / g sugar. It was not until the molasses addition was below 9 % that a statistically significant reduction in yield was observed. Reducing the nitrogen from 0.12 to 0.06 g N / g biomass resulted in a statistically significant decrease of the yield.