Inhibition Effect of Short-Chain Organic Acids on Populations of Mesophilic and Thermophilic Bacteria in a Simulated Food Waste Composting Process

Low pH in the initial phase of composting is mainly due to production of short-chain organic acids. In this study, the orthogonal experiments were designed ingeniously to observe the pH change and inhibition extent of the short-chain organic acids (acetic, butyric, lactic, and propionic acids) on the mesophilic and thermophilic bacteria in a simulated composting process, and the experimental data obtained were subjected to analysis of variance (ANOVA). The results showed that the four organic acids had a negative effect on microbial population, among which, propionic acid had the strongest inhibition on thermophilic bacteria with the weakest acidity. The possible mechanism is that the inhibition in the initial stage of composting process is caused by both acidity and biological toxicity from the organic acids added.