Solid‐state ethanol fermentation by means of inert gas circulation

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Abstract
A new method for solid‐state ethanol fermentation (the SSEF system) was experimented on for the ethanol production from solid starchy materials, where a packedbed‐type fermentor was used. Both cultivation of Aspergillus saitoi and enrichment of a saccharifying enzyme were effective for hydrolysis of the starch. Ethanol production was set in by a form of parallel fermentation using a respiration‐deficient mutant of Saccharomyces cerevisiae. Produced ethanol was simultaneously stripped by circulating inert gas and separated in a condenser. Average ethanol concentration in the condensate was over 200 g/L, and over 90% of produced ethanol was recovered from the packed bed during 15 or 16 days of stripping. The fermentation efficiency was about 80%, which was evaluated much higher than those of conventional solid‐state fermentations. The residue had lesser volume and a higher solids content compared with the distillery wastewaters of conventional liquid‐state fermentations. This means an advantage for the treatment and the effective conversion of the residue into fetilizers or animal feeds.