Water reclamation and value-added animal feed from corn-ethanol stillage by fungal processing

• Published in: Bioresource technology 2014-01, Vol.151, p.284-290
• Main Authors: Rasmussen, M.L., Khanal, S.K., Pometto, A.L., van Leeuwen, J. (Hans)
• Format: Article
• Language: English
• Subjects: Acetic Acid - metabolism; Amino Acids - metabolism; Animal Feed; Biological and medical sciences; Biological Oxygen Demand Analysis; Biomass; Corn; Ethanol; Ethanol - chemistry; Ethyl alcohol; Evaporation; Fundamental and applied biological sciences. Psychology; Fungal process; Fungal Proteins - metabolism; Fungi; Glycerol - isolation & purification; Inoculation; Lactic Acid - metabolism; Oils; Organic Chemicals - isolation & purification; Oxygen - analysis; Plants (organisms); Rhizopus - growth & development; Rhizopus - metabolism; Rhizopus oligosporus; Solubility; Stillage; Thin stillage; Water - chemistry; Water reuse; Zea mays - chemistry
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2013.10.080

•Innovative water reclamation, energy savings and additional coproducts.•Removes recycling inhibitors, i.e. lactic/acetic acid, glycerol, suspended solids.•Fungal biomass has high protein, valuable amino acids suitable for non-ruminants.•Fungal biomass could also potentially be raw material for chitin and chitosan.•Fungal cultivation on thin stillage could make ethanol production more sustainable. Rhizopus oligosporus was cultivated on thin stillage from a dry-grind corn ethanol plant. The aim of the research was to develop a process to replace the current energy-intensive flash evaporation and make use of this nutrient-rich stream to create a new co-product in the form of protein-rich biomass. Batch experiments in 5- and 50-L stirred bioreactors showed prolific fungal growth under non-sterile conditions. COD, suspended solids, glycerol, and organic acids removals, critical for in-plant water reuse, reached ca. 80%, 98%, 100% and 100%, respectively, within 5d of fungal inoculation, enabling effluent recycle as process water. R. oligosporus contains 2% lysine, good levels of other essential amino acids, and 43% crude protein – a highly nutritious livestock feed. Avoiding water evaporation from thin stillage would furthermore save substantial energy inputs on corn ethanol plants.