Bioprocesses for Fuel Production
Dr. Kohn’s laboratory recently demonstrated that end products of fermentation are near equilibrium with each other. Interventions that affect one or more pathways of fermentation result in direct changes in some end product concentrations, causing other end product concentrations to adjust to maintain equilibrium. Because thermodynamic equilibrium can be readily determined based on chemical analysis of substrate and products, what appeared to be complex responses to treatments can be explained with fairly simple mathematical models. This knowledge greatly simplifies explanation and prediction of factors that shift fermentation end products. The effect of interventions can be understood by calculating changes in free energy among end products and by using isotope labels to quantify bidirectional flows. This previous research was conducted using the cow’s rumen (first stomach chamber) where feed fermentation occurs. The thrust of future research will be to extend this approach to other fermentation systems including bio fuel production (e.g. ethanol, methanol, methane, hydrogen, and bio-electric) from grain, fiber and waste. Similar methods will be employed including thermodynamic analysis, in vitro fermentation and perturbation studies, and mass spectrometry for isotope labeling studies
Understanding the thermodynamics and kinetics of fermentation may enable us to manipulate the fermentation systems that produce bio-energy products, and evaluate the feasibility of altering the fermentation in desired ways. For example, in order to determine what enzymes to introduce or genes to up regulate, we need to know what pathways are enzyme limited.
Use of Byproducts as Animal Feeds
Byproducts of ethanol fermentation (distillers grain) are high in phosphorus and have a low quality of protein for animal production. Feeding increasing amounts of these feeds, may be cost effective for many dairy and beef operations, but the diets are oversupplied with the nutrients phosphorus and nitrogen which end up in animal manure, and ultimately in water or air resources. Potential use of cellulosic byproducts as feeds is unexplored, but may be a way to reduce waste from ethanol production and increase efficiency of animal production. Understanding the nutrient management consequences of increased use of distillers byproducts will have an economic and environmental benefit.