(290f) Media Requirements for Aerobic Cultivation of Saccharomyces Cerevisiae TMB 3400-F30-3 On Undetoxified Softwood Dilute Acid Hydrolyzate

Authors: 
Häggström, C., Luleå University of Technology
Hodge, D., Michigan State University
Rova, U., Luleå University of Technology
Brandberg, T., SEKAB E-Technology


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 for subsequent fermentation of dilute acid hydrolyzed softwood. This xylose-utilizing yeast is a promising ethanologen for converting lignocellulosic biomass sugars to ethanol. The dilute acid pretreated softwood hydrolyzate used in the process 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 6.7 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.