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Abstract
A NADH dehydrogenase was solubilized and partially purified from Pediococcus halophilus, which is capable of lowering the redox potential of the growth medium. The enzyme is specific for NADH. 2,6-Dichlorophenolindophenol, ferricyanide, NBT and especially various quinones can act as electron acceptors. The optimum pH for the activity was pH 6.0 and the optimum NaCl concentration was found to be 10 ~ 15% (w/v). The enzyme was inhibited by SH-reagents, p- chloromercuribenzoate and HgCl2, but not by EDTA. None of the tested strains which were unable to lower the redox potential possessed the NADH dehydrogenase. A coincidental relationship was observed between the NADH dehydrogenase activities and the abilities to reduce the redox potential of several soy pediococcal strains.
It was observed that the addition of some quinones caused a noticeable increase in the browning rate of moromi juice in an early stage of soy sauce brewing (MJ). These results suggest that NADH dehydrogenase plays a substantial role in the depression of browning of MJ by rH-lowering soy pediococci.