Effects of Temperature Fluctuation on the Anaerobic Digestion Characteristics and Evolution of Microorganisms of Kitchen Waste

Water accounts for 70 % - 90 % of the total mass of food waste, and the contents of organic matter, oil, and salt in the waste are high. These conditions are highly suitable for the growth and reproduction of bacteria and other microorganisms. Therefore, anaerobic digestion is a common approach to treat food waste. Despite its long history, the research on anaerobic digestion has gradually developed with the progress in science and technology. This study aimed to explore the influence of temperature fluctuation on the anaerobic digestion characteristics of food waste by performing batch experiments; also, the characteristics were analysed from a microscopic perspective. The anaerobic digestion process was subjected to the interactions between various microorganisms and enzymes. The experimental results indicated that the activity of bacteria belonging to the phyla such as Proteobacteria and Chloroflexi was relatively high at a constant temperature. In contrast, the activity of the bacteria belonging to the phyla such as Bacteroidota and Acidobacteriota was relatively high at regulated temperatures. The activity of cellulase and lipase increased whereas that of protease decreased at a constant temperature. Regardless of the fluctuation mode of temperature, the activity of amylase did not obviously alter. These microorganisms with different responses to temperature fluctuation had unique functions in the anaerobic digestion process, and they participated in different anaerobic digestion stages. Therefore, based on the attribute of kitchen waste, an appropriate temperature mode can be selected to make anaerobic digestion more efficient.