title: Investigation of nutrient feeding strategies in a countercurrent mixed-acid multi-staged fermentation: development of segregated-nitrogen model.
abstract: The MixAlco process is a biorefinery based on the production of carboxylic acids via mixed-culture fermentation. Nitrogen is essential for microbial growth and metabolism, and may exist in soluble (e.g., ammonia) or insoluble forms (e.g., cells). Understanding the dynamics of nitrogen flow in a countercurrent fermentation is necessary to develop control strategies to maximize performance. To estimate nitrogen concentration profiles in a four-stage fermentation train, a mass balance-based segregated-nitrogen model was developed, which uses separate balances for solid- and liquid-phase nitrogen with nitrogen reaction flux between phases assumed to be zero. 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 nitrogen loading patterns, (2) develop a reaction-based model, (3) understand influence of model inputs (e.g., operating parameters, feedstock properties, nutrient loading pattern) on the steady-state nitrogen profile, and (4) determine the direction of the nitrogen reaction flux between liquid and solid phases.
authors.affiliation: Texas A&M University, Dept. of Chemical Engineering, 624 Jack Brown Building, College Station, TX 77843, USA. AaronSmith328@gmail.com
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Smith
authors.forename: Mark T
authors.initials: MT
authors.lastname: Holtzapple
mesh_terms: D001709:Biotechnology / Q000379:methods*; D002244:Carbon / Q000032:analysis; D003377:Countercurrent Distribution; D005285:Fermentation / Q000502:physiology*; D008954:Models, Biological; D009584:Nitrogen / Q000032:analysis*; D012995:Solubility
chemical_list: D002244:Carbon; D009584:Nitrogen