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[Display omitted] • The effect of acetate to butyrate ratio in electron acceptor (EA) on CCE was studied. • The higher content of butyrate in feedstock led to the higher production of caproate. • The maximum production of caproate was 3.7 ± 0.3 g·L−1, when butyrate was the only EA. • Butyrate would be selected as EA only when acetate was much lower than butyrate. • Metagenomic analysis proved that high butyrate content strengthened the CCE process. This study investigated the effect of electron acceptor (EA) distribution (acetate to butyrate ratio) on the carbon chain elongation (CCE) process. The results showed that the higher content of butyrate in the initial material led to the higher production of caproate. The maximum production of caproate was 3.74 ± 0.30 g·L−1, which was obtained when only butyrate was added as EA. Little caproate but much butyrate was produced where only acetate was added as EA. This indicated that CCE bacteria preferentially selected acetate as the EA to produce butyrate, and butyrate could be selected as EA to produce caproate only when the acetate content was much lower than butyrate. Unclassified_f_Dysgonomonadaceae , Massilibacterium , and Seramator were the predominant bacteria. Functional enzyme analysis showed that high butyrate content strengthened the fatty acid biosynthesis pathway and reverse β-oxidization pathway. The findings showed the importance of butyrate in CCE for caproate production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Provides a new idea for the recycle and harmless treatment of AMD. • More than 99% terramycin was reduced after adding HCMI of compost. • By adding HCMI, Qac B and tet H decreased by 0.35, and 0.15%, respectively. • The succession of microorganism had greatly factor on the varies of ARG subtypes. • The HCMI improve the removal rate of ARG subtype to a certain extent. In order to tackle the issue of terramycin mycelial dreg (TMD) diagnosis and removal of terramycin and antibiotic resistance genes (ARGs), this study adopted aerobic composting (AC) technology and added homemade compound microbial inoculum (HCMI) to promote the AC of TMD and enhance the removal of terramycin and ARGs. The findings demonstrated that terramycin residue could be basically harmless after AC. Moreover, HCMI not only reduced Qac B and tet H but also increased the degradation rates of Van RA, Van T, and dfr A24 by 40.81%, 5.65%, and 54.18%, respectively. The HCMI improved the removal rate of ARG subtypes to a certain extent. According to redundancy analysis, during AC, the succession of the microbial community had a stronger influence on the variance of ARG subtype than the environmental conditions. Differences in the abundance of various bacteria due to changes in temperature may be an intrinsic mechanism for the variation of ARG subtypes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Established a high lignocellulosic dry-wet combined anaerobic digestion system. • The kinetic parameters of the whole anaerobic digestion process were revealed. • Synergism between Clostridiales and methanogens was evaluated via network analysis. • Syntrophy between SFOB and methylotrophic Methanospirillum was observed. • The number of key acidogenic Clostridium was increased by 80.77–107.11%. Dry-wet combined anaerobic digestion is a novel approach for treating lignocellulosic waste by increasing the organic load of reactor while accelerating the conversion of organic acids. Here, we investigated the effect of regulated substrate ratios and initial pH in the dry acidogenesis stage on the bioconversion efficiency of dry-wet combined anaerobic digestion. Our data revealed microbial interactions and further identified key microbes based on microbial co-occurrence network analysis. On day three of acidification, the kinetic hydrolysis rate and acidification yield reached 1.66 and 60.07%, respectively; this was attributed to enhancement of the synergistic effect between Clostridiales and Methanosaeta , which increased the proportion of corn straw in the substrate or lowered the initial spray slurry pH to 5.5–6.5. With increased acidification capacity, acetoclastic methanogens were enriched in the wet methanogenesis stage; the syntrophic effect of Syntrophomonadales , Syntrophobacterales and Methanospirillum , meanwhile, was enhanced, leading to an overall improvement in biogas production. [ABSTRACT FROM AUTHOR]