Characterization of microbial community and main functional groups of prokaryotes in thermophilic anaerobic co-digestion of food waste and paper waste

Highlights: • Effect of paper waste on microbial community in thermophilic digestion was clarified. • Functional groups of prokaryotes changed greatly as the paper waste ratio increased. • Community of cellulose-degrading bacteria changed greatly due to declined pH value. • Hydrogenotrophic methanogenesis was enhanced when the paper waste ratio ≥ 50%. • The predominant microorganism response for each metabolic step was summarized. -- Abstract: The thermophilic anaerobic co-digestion of food waste and paper waste was successfully operated with a 0% to 70% fraction of paper waste. The variation of functional microbial community was investigated by 16S rRNA gene analysis. The results indicated that the hydrolyzing bacterial community changed from carbohydrate/protein-degrading bacteria to cellulose-degrading bacteria when the paper waste ratio was higher than 50%. Significant changes in the taxon responsible for cellulose degradation were found depending on the paper waste fraction. Cellulose-degrading bacteria outcompeted lactic acid bacteria in the degradation of monosaccharide, resulting in a decline in the proportion of lactic acid bacteria and the absence of an accumulation of lactic acid. At high paper waste ratios, because the cellulose-degrading bacteria, such as Defluviitoga tunisiensis, were more likely to degrade monosaccharides directly to acetate and hydrogen rather than to propionate and butyrate, the abundance of syntrophs was reduced. The variation of those bacteria with high H₂-producing ability significantly influenced the proportion of hydrogenotrophic archaea. The change in the microbial community as the paper waste fraction increased was illustrated with regard to anaerobic degradation steps.