Stress of pH and acetate on product formation of fermenting polysaccharide-rich organic waste

Effects of stress of pH and/or acetate on the fermentation product formation of polysaccharide-rich organic waste were examined in this work, with externally dosed acetate (up to 333 mmol l−1) and adjusted pH (5–9). Ethanol, acetate, and lactate were the main metabolites. Concentrations and dissociation states of acetate affected the productions of ethanol and lactate. With dosed acetate, ethanol was favorably produced at pH 6, but was completely inhibited at pH 5. On the other hand, lactate was less favorably produced with dosed acetate, but was also completely inhibited at pH 5. With no externally dosed acetate, the metabolism gradually shifted from acetate to lactate and ethanol-forming pathway with fermentation. With dosed acetate, except for at pH 5, the pathway to ethanol was strengthened with time. The acetate stress on product formation was stronger than from pH stress.