The role of starch-degrading mycelial fungi, and the alcohol production and ethanol tolerance of the yeasts isolated from selected
Vietnamese traditional rice wine starters were examined, and optimum conditions for these essential steps in rice wine fermentation
were determined. Of pure isolates from Vietnamese rice wine starters, mould strains identified as Amylomyces rouxii, Amylomyces
aff.rouxii, Rhizopus oligosporus and Rhizopus oryzae, were superior in starch degradation, glucose production and amyloglucosidase
activity during the saccharification of purple glutinous rice. A. rouxii was able to produce up to 25%w/w glucose with an
amyloglucosidase activity up to 0.6 U g1 of fermented moulded mass. Five yeast isolates identified as Saccharomyces cerevisiae were
selected for their superior alcohol productivity. They were able to deplete a relatively high initial percentage of glucose (20% w/v),
forming 8.8% w/v ethanol. The ethanol tolerance of S. cerevisiae in challenge tests was 9–10% w/v, and 13.4% w/v as measured in
fed-batch fermentations. Optimum conditions for the saccharification were: incubation for 2 d at 341C, of steamed rice inoculated
with 5 log cfu g1
; for the alcoholic fermentation 4 d at 28.31C, of saccharified rice liquid inoculated with 5.5 log cfu mL1
.
r 2005 Elsevier Ltd. All rights reserved.
Keywords: Rice wine; Saccharification; Alcoholic fermentation; Fungi; Moulds; Yeasts; Amylomyces; Saccharomyces