title: Controlled pilot development unit-scale fed-batch cultivation of yeast on spruce hydrolysates.
abstract: Yeast production on hydrolysate is a likely process solution in large-scale ethanol production from lignocellulose. The hydrolysate will be available on site, and the yeast has furthermore been shown to acquire an increased inhibitor tolerance when cultivated on hydrolysate. However, due to over-flow metabolism and inhibition, efficient yeast production on hydrolysate can only be achieved by well-controlled substrate addition. In the present work, a method was developed for controlled addition of hydrolysate to PDU (process development unit)-scale aerobic fed-batch cultivations of Saccharomyces cerevisiae TMB 3000. A feed rate control strategy, which maintains the ethanol concentration at a low constant level, was adapted to process-like conditions. The ethanol concentration was obtained from on-line measurements of the ethanol mole fraction in the exhaust gas. A computer model of the system was developed to optimize control performance. Productivities, biomass yields, and byproduct formation were evaluated. The feed rate control worked satisfactorily and maintained the ethanol concentration close to the setpoint during the cultivations. Biomass yields of 0.45 g/g were obtained on added hexoses during cultivation on hydrolysate and of 0.49 g/g during cultivation on a synthetic medium with glucose as the carbon source. Exponential growth was achieved with a specific growth rate of 0.18 h-1 during cultivation on hydrolysate and 0.22 h-1 during cultivation on glucose.
authors.affiliation: Department of Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden. andreas.rudolf@ chemeng.lth.se
authors.forename: Andreas
authors.initials: A
authors.lastname: Rudolf
authors.forename: Gaspard
authors.initials: G
authors.lastname: Lequeux
authors.forename: Gunnar
authors.initials: G
authors.lastname: Lidén
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D018929:Cell Culture Techniques / Q000379:methods*; D049109:Cell Proliferation; D003198:Computer Simulation; D005246:Feedback / Q000502:physiology; D006868:Hydrolysis; D008954:Models, Biological; D028222:Picea / Q000737:chemistry* / Q000382:microbiology*; D010865:Pilot Projects; D012441:Saccharomyces cerevisiae / Q000502:physiology*