Short communicationDewatering investigations on fungal biomass grown in thin stillage from a dry-mill corn ethanol plant

•Fungal biomass grows prolifically in thin stillage from ethanol production.•The fungal density and compressibility make many dewatering approaches ineffective.•Gravity screening followed by centrifugal increased the solids content from 1% to 30%.

An innovative bioprocess utilizing thin stillage from a dry-grind corn ethanol plant was used to produce a useful filamentous fungus (Rhizopus microsporus var. oligosporus) in a pilot-scale bioreactor. The fungal process can improve the economics of corn ethanol production by producing an excellent food supplement for livestock or serving as a feedstock material for producing chitin, chitosan, and glucosamine. However, in order to be economically viable, effective and low-cost mechanical dewatering of the fungal biomass grown in thin stillage is required. In this study, dewatering tests were performed on fungal biomass using gravity and centrifugal sedimentation, gravity screening, a belt filter, a filter press, and centrifuge filtration in order to determine the most effective dewatering methods for this application. Utilizing a gravity-fed concave screen followed by a centrifuge filter proved to be the most effective dewatering approach and increased the screenable solids (i.e., larger than 20 mesh) content of the fungal biomass from the bioreactor from 1% to 30%. Achieving a solids content greater than 30% with mechanical dewatering is unlikely because of theoretical limits due to intracellular water. Nonetheless, this degree of dewatering greatly reduces thermal drying costs necessary to obtain a final product with a moisture content of 10%.

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