Description:
The addition of zero-valent iron and magnetite to increase ethanol and lactic acid fermentation yields from food waste is a promising approach. This study compared the effects of 50-nm and 500-nm particle sizes of zero-valent iron and magnetite on ethanol and lactic acid fermentation and analyzed the mechanism of action from the perspective of organic matter material transformation and microbiology. The experimental results showed that 500-nm particle size magnetite and zero-valent iron could promote the hydrolysis of polysaccharides and proteins. 500-nm particle size magnetite could increase ethanol production (1.4-fold of the control), while 500-nm particle size zero-valent iron could increase lactic acid production (2.8-fold of the control). The scanning electron microscopy results showed that the ethanol-fermenting microorganisms were dominant in the anaerobic fermentation ethanol production system of food waste. The anaerobic fermentation lactic acid production system of food waste had a community structure with multiple bacteria coexisting.Metagenomic analysis showed that 500-nm magnetite increased the level of amino acid metabolism functional genes (1.9-fold of the control), while 500-nm zero-valent iron increased the level of glycoside hydrolase genes (1.3-fold of the control). These findings can provide a reference for increasing the anaerobic fermentation yield of food waste