furthermore, the neutral condition favored the chain elongation of carboxylic acids, especially
with ethanol as the electron donor. Ethanol addition enhanced valeric acid and caproic acid production by
44% and 167%, respectively. Lactic acid addition also had positive effects on VFAs production under the
neutral condition but limited to C2–C4 products. As a result, propionic acid and butyric acid production
was increased by 109% and 152%, respectively. These findings provide substantial evidence for regulating
carboxylic acid production during mixed culture fermentation of BSG by controlling pH and adding
electron donors.