Grant: Discovery Grants Program - Individual

The objective of the proposed research is to optimize the fermentation of waste or low cost substrates for the production of renewable fuels and chemicals, with an emphasis on the fermentation of difficult to ferment pentose (five carbon) sugars. The use of lignocellulosic biomass to produce renewable fuels results in large reductions in greenhouse gas emissions compared to using fossil fuels or even compared to using ethanol from corn. Examples of potential low cost substrates include waste lignocellulosic biomass from the forestry industry, various pulp mill streams, and mountain pine beetle killed wood. In addition to environmental benefits, using low value mountain pine beetle killed wood for biorefinery feedstock will help increase economic diversification in affected areas, and increasing the number of products produced at pulp mills would decrease sensitivity to changes in pulp prices. Unlike conventional fermentation substrates, substrates produced from lignocellulosic biomass contain many inhibitors. Current fermentation obstacles include the need for pretreatment to detoxify the substrate, and the difficulty of fermenting pentose sugars. Pentose fermentation is generally slow, sensitive to inhibitors, and requires genetically modified organisms. One strategy to work with less than ideal fermentation substrates and the resulting low fermentation rates is to use continuous fermentations with cell recycle. The optimum yeast growth rate, aeration levels, nutrient addition, and reactor hydraulics will be found in order to eliminate the need for expensive hydrolysate detoxification, maximize product yield, and minimize by-product formation. Results will be directly applicable to current industrial fermentations of sulfite pulp mill wastewaters, and also to the fermentation of other difficult to ferment substrates projected to be a part of biomass refineries, such as hemicellulose streams from Kraft pulping and biomass hydrolysates from forestry waste.