Production of ethanol and biomass from thin stillage by Neurospora intermedia: A pilot study for process diversification

Abstract

Dry mill ethanol processes produce ethanol and animal feed from whole grains, where the wastewater after the distillation and separation of solid materials is called "thin stillage." In this work, similar production of ethanol (3.5 g/L) and biomass (5 g/L) from thin stillage was obtained during batch cultivation of the edible fungus Neurospora intermedia in a 2-m high airlift reactor and bubble column. The fungal biomass, containing 50% w/w protein and 12% w/w lipids, was rich in essential amino acids and omega-3 and -6 fatty acids. In a continuous mode of fermentation, dilution rates of up to 0.2 h-1 could be applied without cell washout in the bubble column at 0.5 vvm. At 0.1 h-1, around 5 g/L of ethanol and 4 g/L of biomass containing ca. 50% w/w protein were produced. The fungus was able to assimilate saccharides in the liquid fraction as well as sugar backbones such as xylan and arabinan in the solid fraction. The inclusion of the current process could potentially lead to the production of 11 000 m3 of ethanol (5.5% improvement vs. normal industrial process) and around 6300 tons of high-quality biomass for animal feed at a typical facility producing 200 000 m3 ethanol per year.