(770c) Nutrient Supplementation Key to Inhibitor-Tolerant Yeast Development and Fermentation Performance On Switchgrass Hydrolyzates

Inhibitory compounds generated during acid hydrolysis pretreatment of lignocellulosic biomass interfere with subsequent fermentation to ethanol.  Tolerant yeast strains have recently been developed by targeted evolution in the presence of biomass hydrolyzate inhibitors.  In order to optimize performance, comparative data were collected on both the tolerant and parent strains in experiments testing the impact of nitrogen sources, vitamins, and minerals on ethanol production potential.  With respect to optimal ethanol production, a striking difference in the nutritional requirements of parent and adapted strains was observed in both synthetic media and dilute acid hydrolyzates of switchgrass that were supplemented with a variety of commercially available nitrogen sources.  Since nutrient availability significantly impacted both ethanol yield and production kinetics, and was strain-dependent, nutrient supplementation requirements were considered in the evaluation and ranking of tolerant isolates as well as in the subsequent optimization and design of hydrolyzate fermentation processes.