Effects of zero-valent iron and magnetite on ethanol and lactic acid production in the anaerobic fermentation of food waste.

With the increasing global concern about food waste management, finding efficient ways to convert it into valuable products is crucial. The addition of zero-valent iron and magnetite to enhance ethanol and lactic acid fermentation yields from food waste emerges as a potential solution. 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). Metagenomic analysis showed that 500-nm magnetite increased the abundance of genes for amino acid metabolic functions, while 500-nm zero-valent iron increased the abundance of glycoside hydrolase genes (1.3-fold of the control). It's worth noting that while these findings are promising, they are based on controlled experimental conditions, and real-world applications may vary. his research not only offers a novel approach to augmenting anaerobic fermentation yields but also contributes to sustainable food waste management practices, potentially reducing environmental impacts and creating valuable products.

Effects of iron additives on the removal of antibiotics and antibiotic resistance genes in anaerobic fermentation of food waste.

The presence of antibiotics and antibiotic resistance genes (ARGs) in food waste (FW) during anaerobic fermentation poses significant environmental and health risks. This study elucidated the potential of iron additives, specifically 500-nm and 50-nm zero-valent iron (ZVI) and magnetite, in mitigating these contaminants. These findings revealed that 500-nm magnetite significantly reduced tetracyclines by 81.04%, while 500-nm ZVI effectively reduced cefotaxime by 89.90%. Furthermore, both 500-nm and 50-nm ZVI were observed to decrease different types and abundance of heavy metal resistance and virulence genes. Interestingly, while 500-nm ZVI reduced the overall abundance of ARGs by 50%, 500-nm magnetite primarily reduced the diversity of ARGs without significantly impacting their abundance. These results elucidate the efficacy of iron additives in addressing antibiotic contamination and resistance during the anaerobic fermentation process of FW. The findings acquired from this study mitigate the development of innovative and environmentally sustainable technologies for FW treatment, emphasizing the reduction of environmental risks and enhancement of treatment efficiency.

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As antibiotics and heavy metals are often mixed in animal feed, their excretion through animal feces would cause bacteria to produce antibiotic resistance genes and heavy metal resistance genes. The pollution of antibiotics resistance gene and heavy metal resistance gene has become a major threat to human health and ecological environment. From the perspective of bacterial evolution, we proposed the importance of bacterial long-term evolution experiments about antibiotics and heavy metals. There is a complex co-selection resistance between antibiotic resistance genes and heavy metal resistance genes, which interact with each other and collectively determine the environmental behavior of bacteria. Horizontal transfer of resistance gene increases its variability in the environment. Mobile genetic elements play an important role in horizontal transfer of resistance gene. As for resistance gene pollution control, advanced oxidation technology has a good resistance gene removal effect. The UV/TiO2 oxidation technology can reduce the abundance of antibiotic resistance genes of 4.7-5.8 log, with an efficiency of >99.99%. Other control strategies, such as the use of Macleaya cordata extract and the combination of bacteriophage and antibiotics, are also of significance for controlling resistance genes.