Evaluation of Aerobic Propagation of Yeasts as Additional Step in Production Process of Corn Ethanol

Abstract

Yeast is one of the co-products of ethanol plants, which can be used as a nutritional supplement in animal feed due to its high protein content. Given the importance of yeast contribution to the nutritional properties of DDG (dried distillers’ grains), the aim of this study was to assess how different levels of aeration affect the biomass production and the quality of yeast providing new insights into yeast production, offering an alternative source of income for the corn ethanol industry. For this purpose, yeasts were grown in a fed-batch process, and different concentrations of aeration in the medium were tested, namely 0.5, 1.0, and 1.5 volume of air per volume of wort per minute (v v−1 min−1). At the end of the cellular biomass production process, yeasts grown with 0.5 (v v−1 min−1) aeration in the reactor showed higher biomass formation (19.86 g L−1), cellular yield (g g−1), and a lower formation of succinic acid (0.70 g L−1) and acetic acid (0.11 g L−1). Aeration influenced an increase of 1.0% in the protein content in yeast. In conclusion, lower levels of aeration in the yeast production process enables more efficient sugar utilization for biomass formation and is a potential strategy to increase the protein content and the commercial value of DDG.

Keywords

• aeration
• biomass production
• cell growth
• dried distillers’ grains
• nutrition
• oxidative stress