Lactic acid fermentation of potato pulp by Rhizopus oryzae IFO 5740

Abstract

Thirty-eight strains of the fungus Rhizopus oryzae were grown on potato pulp, an agricultural byproduct of the starch industry. Either lactic acid or fumaric acid and ethanol were formed, and the ratio differed among the strains tested. The highest amount of L(+)-lactic acid (11.2 mg/g fresh matter) was observed in the pulp fermented for six days by R. oryzae IFO 5740. The IFO 5740 strain rapidly reduced the hardness and pH of potato pulp within one day followed by the gradual synthesis of lactic acid. A composition analysis showed that the enzymes secreted from the fungal cells hydrolyzed starch efficiently with partial degradation of the cell wall. R. oryzae IFO 5740 may be used as an inoculant for ensiling potato pulp and other agricultural by-products containing starch.