Ethanol and Protein from Ethanol Plant By-Products Using Edible FungiNeurospora intermediaandAspergillus oryzae

Abstract

Feasible biorefineries for production of second-generation ethanol are difficult to establish due to the process complexity. An alternative is to partially include the process in the first-generation plants. Whole stillage, a by-product from dry-mill ethanol processes from grains, is mostly composed of undegraded bran and lignocelluloses can be used as a potential substrate for production of ethanol and feed proteins. Ethanol production and the proteins from the stillage were investigated using the edible fungiNeurospora intermediaandAspergillus oryzae, respectively.N. intermediaproduced 4.7 g/L ethanol from the stillage and increased to 8.7 g/L by adding 1 FPU of cellulase/g suspended solids.Saccharomyces cerevisiaeproduced 0.4 and 5.1 g/L ethanol, respectively. Under a two-stage cultivation with both fungi, up to 7.6 g/L of ethanol and 5.8 g/L of biomass containing 42% (w/w) crude protein were obtained. Both fungi degraded complex substrates including arabinan, glucan, mannan, and xylan where reductions of 91, 73, 38, and 89% (w/v) were achieved, respectively. The inclusion of the current process can lead to the production of 44,000 m3of ethanol (22% improvement), around 12,000 tons of protein-rich biomass for animal feed, and energy savings considering a typical facility producing 200,000 m3ethanol/year.