In situ preparation of oriented microbial consortium-based compound enzyme strengthens food waste disintegration and anaerobic digestion: Performance, mechanism, microbial communities and global metabolic pathways

This study used food waste (FW) as the substrate, under the co-culture system, innovatively developed the oriented and high matching degree microbial consortium-based compound enzyme (MCE) used for promoting FW hydrolysis and anaerobic digestion (AD). It was found that the highest hydrolysis efficiency and substrate biodegradability could be obtained after 1:100 MCE (i.e. the inoculation ratio of Aspergillus oryzae CICC 40214 as protease generator and Aspergillus niger CICC 40294 as amylase generator was 1:100) pretreatment, thereby harvesting the highest biomethane yield of 522.61 mL/g VS. The dissection of FTIR results indicated that the structure of main components of starch, protein and lipid in FW was destructed after MCE pretreatment, of which the protein was more susceptible to MCE and disintegrated first, while its structure also became looser. XPS C1s spectra and N1s spectra showed that the C-(C/H) and protein-N of the enzyme pretreated solid were respectively decreased from 77.82 % to 69.19 % and 69.43 % to 40.07 %, which further implied that more carbohydrates and proteins were released from solid phase to liquid phase after MCE pretreatment. The microbial community and metagenome analysis illustrated that MCE pretreatment regulated the microbial communities lead to a shift in the favorable direction of biomethane production. While based on the changes in gene abundance, the deciphering of global metabolic pathways revealed that the 80 %, 60 %, 75 % and 86 % of the functional genes related to glycolysis, amino acid metabolism, TCA cycle and methane metabolism were respectively intensified after 1:100 MCE pretreatment, thereby achieving the maximized biomethane yield.