Preliminary determination of antibacterial substances during anaerobic preservation of food waste and their effects on methanogenesis

Abstract

Food waste can easily breed bacteria and produce odour during production, collection, transportation, preservation and disposal. This work studied the effects of aerobic preservation and anaerobic preservation on the antibacterial and antiseptic properties of food waste and subsequent methane production by anaerobic fermentation. Compared with aerobic preservation, the concentration of lactic acid produced on the 5th day of anaerobic preservation increased by 2.01 times, the pH decreased rapidly and the number of Escherichia coli was reduced by 99.96% on the 7th day; all these changes could effectively inhibit the activity of spoilage bacteria. The results of the biological toxicity test showed that lactic acid and acetic acid were the main antibacterial substances in anaerobic preservation. The biological toxicity of lactate or acetate was significantly lower than that of the corresponding organic acid molecules. When food waste enters the anaerobic digestion reactor after preservation, materials with high lactic acid concentration are greatly diluted, which will not affect the methane fermentation process, but can lead to elevate biogas production. These observations are consistent with the conclusion obtained by kinetic analysis that anaerobic preservation has a faster hydrolysis rate and a shorter system stagnation period than aerobic preservation. Therefore, anaerobic preservation is a suitable way of storing food waste, and it can promote methane fermentation.