Carbon stable isotopic compositions of glucose and ethanol in sake after simultaneous saccharification and fermentation processes

Carbon stable isotopes of glucose during the degradation of rice by the koji fungus Aspergillus oryzae

“…In this case, sake lees typically comprise 45 % of the total ingredient rice weight for premium varieties such as ginjo and daiginjo sake ( n = 826) [ 34 ]. Although the δ 13 C values of glucose are retained from the ingredient rice throughout saccharification, the resulting sake after SSF exhibits δ 13 C values of glucose that are ∼1 ‰ more positive than that of the ingredient rice [ 25 ]. This discrepancy is roughly half of the carbon isotope discrimination observed during the single fermentation step of winemaking, where grape sugar is converted to ethanol [ [35] , [36] , [37] ].…”

“…The carbon stable isotopic composition (expressed as δ 13 C) of glucose has potential as an indicator of carbon dynamics and as a tool for authenticating the origin of Japanese fermented foods. Previous studies have investigated the utility of δ 13 C values in sake produced via simultaneous saccharification and fermentation (SSF) processes [ [24] , [25] , [26] ]. However, the variation in the δ 13 C value of glucose generated solely from rice starch by A. oryzae -derived hydrolytic enzymes remains unknown.…”