Improvement of the yeast protein content in a continuous hemicellulose hydrolysate fermentation

Abstract

With projections foreseeing a significant rise in the world’s population, the demand for food is expected to soar, posing unprecedented challenges to food production and distribution systems. Traditional agricultural expansion methods, often involving deforestation and environmentallydetrimental monocultures, are increasingly unsustainable, particularly as e↵ortsto curb CO2 emissions intensify.This master thesis investigates the enhancement of the yeast single cell protein (SCP)content in a continuous fermentation using hemicellulose hydrolysate, a waste product frommultiple agricultural sectors. In collaboration with Vogelbusch Biocommodities within the EU IMPRESS project, the research aims to create a sustainable alternative to soybean as a protein additive in animal feed.A fed-batch fermentation system was successfully converted to continuous fermentation with a synthetic hemicellulose hydrolysate medium, demonstrating improved efficiency and productivity in SCP production. Shake flask experiments optimised growth medium compositions,while continuous fermentation established ideal conditions for stable and productiveSCP production. The results demonstrated a 35% increase in protein yield, reaching apeak of 0.200 g.g-1, through adjustments in feed concentrations and compositions. Proteinproductivity was increased to 7.59 g.l-1h-1, a 15% increase from initial levels.Transitioning from synthetic medium to hemicellulose hydrolysate presents challengesdue to potential inhibitory compounds and fluctuating sugar compositions. However, the scalability of the project suggests the feasibility of using diverse hydrolysates for efficient SCP production. Future research avenues include genetically modified yeasts for improvedsubstrate utilisation and exploration of optimal dilution rates to maximise productivity.