Insight into the evolution of phosphorous conversion, microbial community and functional gene expression during...

Garlic and chili are widely used as food flavoring agents in food cooking, therefore might be accumulated in large amounts in food waste (FW). The effects of garlic and chili on the dissolution, hydrolysis, acidification and methanation in an anaerobic co-digestion system were investigated during the combined co-digestion of FW and excess sludge (ES). Additionally, the transformation of phosphorus form and microbial metabolism changes during the process were analyzed. The results showed the addition of garlic and chili promoted the release of protein in the soluble chemical oxygen demand. Secondly, the addition of garlic and chili up-regulated the relative abundances of key coding genes pstS, pstA, pstB and pstC. The relative abundances of the pstS and pstC genes increased by 0.0113% and 0.0021%, respectively, when 10 g garlic was added compared with no garlic. Furthermore, with respect to phosphorus conversion, the addition of garlic inhibited the conversion of solid phosphorus to gaseous phosphorus, whereas the addition of chili had the opposite effect. Meanwhile, garlic and chili inhibited the expression of key coding genes in phosphofructokinase. This work provides new insights into the phosphorus conversion and microbial metabolism in the process of anaerobic co-digestion of FW and ES under the influence of spicy substances.