Yeast as single cell protein - optimization of medium compositions and process parameters

Abstract

There is an increasing global demand for protein, due to an increased aging population and changing diets favouring increased consumption of animal protein. Using agriculture to produce animal protein requires large areas of farmland and is associated with high emissions of greenhouse gases. Single cell protein (SCP) is microbial protein produced for use in food or feed and could be promising as an alternative protein source due to its high protein content and low fat content, short harvest cycles and being independent from seasons and climate. Efficient production of SCP is highly dependent on process and media design. Yeasts are promising candidates for producing SCP with a near optimal amino acid composition, practical cell size and flocculation abilities which facilitates harvesting.

In this study, the yeasts Blastobotrys adeninivorans, Cyberlindnera jadinii and Wickerhamomyces anomalus were grown on glucose as the main carbon source in a variety of scales and media compositions to assess cell growth by batch cultivation. Additionally, W. anomalus was used for a continuous cultivation experiment. The highest cell dry weight (CDW) obtained during batch cultivation was achieved at 40.23 g/L using W. anomalus with the addition of a vitamin and trace solution to a media containing 100 g/L glucose with yeast extract and meat peptone in a 1.5 L bioreactor. Unwanted ethanol production was prevented in W. anomalus and C. jadinii cultivations by shortening inoculum incubation time, however some unidentified side products were still produced by W. anomalus under some conditions. The continuous cultivation experiment demonstrated that when using a feed rate of 19.062 mL/h the oxygen demand became too high for the bioreactor system to maintain. Achieving a continuous steady-state for this set-up may therefore require using a lower feed rate to increase yield.