Production of protein-rich fungal biomass in an airlift bioreactor using vinasse as substrate

The potential for large-scale production of an edible fungus, Rhizopus oligosporus, on a liquid residue from sugar-to-ethanol production, vinasse, was investigated. An airlift bioreactor (2.5-L working volume) was used for cultivating the fungus on 75% (v/v) vinasse with nutrient supplementation (nitrogen and phosphorus) at 37 °C and pH 5.0. Aeration rates were varied from 0.5, 1.0, 1.5 to 2.0 volumeair/volumeliquid/min (vvm). The fungal biomass yield depended on the aeration rate, and the highest fungal biomass obtained was 8.04 ± 0.80 (gbiomass increase/ginitial biomass) at 1.5 vvm. The observed reductions in organic content by 80% (as soluble chemical oxygen demand) suggest the potential of recycling treated effluent as process water for in-plant use or for land applications. The fungal biomass contained ∼50% crude protein and the essential amino acids contents were comparable to commercial protein sources for aquatic feeds (fishmeal and soybean meal), with the exception of methionine and phenylalanine.