The lactic acid bacterium Tetragenococcus halophila is the dominant species in Indonesian soy mash. Tetragenococcus halophila growing in continuous and retention cultures under defined glucose-limited conditions showed a switch from homolactic (only lactate produced) to mixed acid fermentation (two formate, one acetate and one ethanol formed per glucose) at low growth rates. However, despite low concentrations of sugars present in soy mash and slow growth, no switch to mixed acid fermentation was observed during growth in soy mash. The absence of mixed acid fermentation could not be explained by changes in pH or lactate concentration during growth, indicating that growth in soy mash is not energy-limited. Despite the absence of mixed acid fermentation, an obvious production of acetate, an important soy mash component, is observed in soy mash. The possibility that soy mash components acting as hydrogen acceptors could account for this phenomenon is discussed.