(132a) Optimizing Fermentation Performance through Nutrient Control

The MixAlco process is a biorefinery based on the production of carboxylic acids via the fermentation. Nitrogen is essential for microbial growth and metabolism, and may exist in a soluble or insoluble form. Understanding the dynamics of nitrogen in a countercurrent fermentation is necessary to develop strategies to control nitrogen concentrations, and maximize use. The ability to control a fermentation's C/N profile is critical to maximizing product yield. A mass-balance-based segregated-nitrogen model was developed to estimate nitrogen concentration profiles in a four-stage fermentation train. Comparison of predictions with measured nitrogen profiles from five trains each with a different nutrient contacting pattern shows the segregated-nitrogen model captures basic behavior and is a reasonable tool for estimating nitrogen profiles. The segregated-nitrogen model may be used to 1) estimate optimal nutrient loading patterns, 2) create a reaction-based model, 3) understand influence of model inputs (operating parameters, feedstock properties, nutrient loading pattern, and separation efficiency) on the steady-state nitrogen profile, and 4) determine the direction of the soluble/insoluble nitrogen reaction flux.