Batchwise ethanol fermentation with shochu distillery waste

Abstract

A novel vacuum distillation procedure at low temperature (35–40°C) was applied to shochu distillation to produce a shochu with a mild aroma. The resulting kome (rice) shochu distillery waste contained a large amount of viable yeast (7 × 10 6 cells/ml), glucoamylase activity (70 U/ml), acid protease activity (720 U/ml), and neutral protease activity (420 U/ml). Secondary ethanol fermentation of the mash composed only of glucose as a carbon source and kome or mugi (barley) shochu distillery waste was properly effected. About 10% of ethanol (v/v) was produced in the fermented mash at 30°C within 3 d. In contrast, distillery waste discharged by conventional distillation at high temperature (55–60°C) could not be used for secondary ethanol fermentation at all. The filtrate of secondarily-fermented distillery waste, containing ethanol and possessing a fine aroma fortified with higher alcohols and volatile esters during ethanol fermentation, could be useful for the production of a mirin-like liquor for cooking, Akazake, a characteristic red-colored, sweet alcoholic beverage produced in Kumamoto prefecture only, and a bath additive containing ethanol, a fine aroma, and enzymes. The solid cake of the fermented mash could be used in the same way as conventional sake-kasu, sake-cake. Here, a novel system of utilizing shochu distillery waste, conventionally treated as wastewater, was established economically using a simple vacuum distillation procedure without a need of any complicated process.