Bottlenecks in lignocellulosic ethanol production: xylose fermentation and cell propagation

Conference poster, 2017

A remaining challenge for the development of economically feasible 2nd generation bio-ethanol is low xylose consumption rate and inhibitor tolerance of the utilized Saccharomyces cerevisiae strains. Yeast starter cultures produced for ethanol production in simultaneous saccharification and co-fermentation (SSCF) processes have to meet high, seemingly conflicting requirements. A high biomass yield during propagation is required to produce the high cell concentrations required for the harsh conditions in the proceeding fermentation. Inhibitor tolerance is essential for producing a highly viable starter culture as well as favorable fermentation kinetics. Short-term adaptation of yeast cultures during propagation has been shown to have a positive effect on pentose conversion as well as inhibitor tolerance. Here we propose a model propagation strategy for evaluating physiology of yeast cultures during propagation. This model propagation strategy will be implemented in a study comparing physiology of yeast cultures with and without exposure to lignocellulosic inhibitors during propagation to assess what molecular mechanisms underlie the short-term adaptation response phenotype. For industry, a better control of yeast properties during propagation will result in an improved and consistent performance of yeast starter cultures for SSCF purposes.