Microflora and Selected Metabolites of Potato Pulp Fermented with an Indonesian Starter Ragi Tapé

Abstract

When potato pulp was mixed with Indonesian starter ragi tapé and incubated, both lactic acid and ethanol were gradually formed and attained certain concentrations during 2 days of fermentation. Viable counts of fungi in fresh weight matter, yeasts and lactic acid bacteria after fermentation were 105, 107 and 105 CFU/g, respectively. Denaturing gradient gel electrophoresis of the PCR-amplified internal transcribed spacer of 18S–28S rRNA genes detected Amylomyces rouxii-Rhizopus oryzae, Mucor indicus, Candida tropicalis and Saccharomycopsis fibuligera and revealed that Amylomyces rouxii-Rhizopus oryzae dominated throughout the fermentation period. Amylomyces rouxii cannot be discriminated from the lactic acid-accumulating group of Rhizopus oryzae because the amplified sequences of these fungi were shown to be identical. Morphological characteristics were then studied for Rhizopus-like fungi isolated from fermented potato pulp. Those strains that had produced an enormous number of chlamydospores in the aerial and substrate mycelium were identified as Amylomyces rouxii. The microflora of fermented potato pulp was similar to that made from glutinous rice, namely tapé ketan.

Keywords

• Amylomyces rouxii
• lactic acid fermentation
• ragi tapé