Production of Ethanol and Biomass from Thin Stillage Using Food-Grade Zygomycetes and Ascomycetes Filamentous Fungi

Jorge Ferreira,Patrik Lennartsson,Mohammad Taherzadeh

doi:10.3390/en7063872

Abstract

A starch-based ethanol facility producing 200,000 m3 ethanol/year also produces ca. 2 million m3 thin stillage, which can be used to improve the entire process. In this work, five food-grade filamentous fungi, including a Zygomycete and four Ascomycetes were successfully grown in thin stillage containing 9% solids. Cultivation with Neurospora intermedia led to the production of ca. 16 g·L−1 biomass containing 56% (w/w) crude protein, a reduction of 34% of the total solids, and 5 g·L−1 additional ethanol. In an industrial ethanol production process (200,000 m3 ethanol/year), this can potentially lead to the production of 11,000 m3 extra ethanol per year. Cultivation with Aspergillus oryzae resulted in 19 g·L−1 biomass containing 48% (w/w) crude protein and the highest reduction of the thin stillage glycerol (54%) among the Ascomycetes. Cultivation with Rhizopus sp. produced up to 15 g·L−1 biomass containing 55% (w/w) crude protein. The spent thin stillage had been reduced up to 85%, 68% and 21% regarding lactic acid, glycerol and total solids, respectively. Therefore, N. intermedia, in particular, has a high potential to improve the ethanol process via production of additional ethanol and high-quality biomass, which can be considered for animal feed applications such as for fish feed.

Highlights

IntroductionEthanol has triggered intense commercial interest due to its use in the transport sector as a viable alternative to petroleum fuel
Production of renewable fuels with comparable costs to fossil fuels is a hot topic
Research performed on thin stillage derived from ethanol production using other cereals such as wheat is scarce in literature

Summary

Introduction

Ethanol has triggered intense commercial interest due to its use in the transport sector as a viable alternative to petroleum fuel. In Sweden, the commercial production of ethanol is based on starch, mostly obtained from wheat [3]. Starch-based ethanol processes give rise to two products: ethanol and an animal feed known as dry distiller grains with soluble (DDGS, Figure 1). Considering that the starch-based process gives rise to approximately the same amount of DDGS as ethanol, ca. Research on the overall process leading to the production of feed products has been triggered. In particular, has been considered to be a potential source of further improvement of the overall ethanol process via production of other products such as protein- and lipid-rich biomass [5,6]

Methods

Results

Conclusion