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• A genetically stable mutant strain KT16 was screened by UV-DES compound mutagenesis. • The enzyme activity of KT16 increased by 46.7% compared to the original strain DC8. • Mutagenesis enhanced the ability of S-TE, facilitated the recovery of protein in ES. • Whole genome resequencing analysis of KT16 was performed to detect the mutant sites. Excess sludge (ES), a resource-rich organic waste, can be solubilized by thermophilic enzymes to extract proteins for sludge reduction and resources recovery. To solve the problems of low hydrolysis effect of ES and low enzyme producing ability of wild thermophilic bacteria, ultraviolet and diethyl sulfate (UV-DES) were adopted to mutate thermophilic bacteria in this study. Mutation sites were detected and annotated by whole genome sequencing analysis. The results showed that UV-DES mutagenesis could effectively improve enzyme-producing capacity of thermophilic bacteria and promote the hydrolysis of ES. The protease activity of the mutant strain KT16 was 46.7 % higher than that of the original strain DC8. The protein extraction rate with enzyme produced by KT16 reached 83.3 %. The total content of proteins recycled through KT16 enzyme solution was 3539.6 mg·L-1, 18.4 % higher than that of DC8. This work provided a theoretical idea and technical guidance for the protein recovery from ES. [ABSTRACT FROM AUTHOR]

[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]

Highlights • Swine slaughterhouse waste produced a maximum methane yield of 999.2 mL/g VS. • Lipid hydrolysis led to serious accumulation of linoleic, oleic and palmitic acids. • Increase of palmitic acid produced by degradation of oleic acid was observed. • Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. Abstract This study investigated methane production, long-chain fatty acids (LCFAs) profile, and predominant microorganisms in anaerobic digestion (AD) of lipid-rich swine slaughterhouse waste (SSW). The maximum methane yield was 999.2 mL/g VS. LCFAs, as inhibitory hydrolysis products, accumulated first to 1165 mg/L on day 3, and then decreased sharply to 125.7 mg/L on day 9, and finally were degraded to 20 mg/L on day 27. Linoleic acid (C18:2), oleic acid (C18:1) and palmitic acid (C16:0) were the dominant LCFAs. The easy conversion of C18:1 to C16:0 compared with difficult degradation of C16:0 resulted in an increase of C16:0 on day 4–6. Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. This study proved the high methane potential of lipid-rich SSW and gained insights into the degradation process by analysis of intermediates of LCFAs and predominant microorganisms. The results can provide valuable guidance for efficient utilization of this waste to produce methane in future. [ABSTRACT FROM AUTHOR]

• The property of AMRs biochar has been improved by H 3 PO 4 -modification. • The using of PBC as carrier to load nZVI improved the agglomeration of Fe particles. • PBC and nZVI/PBC enhanced biogas yield by more than 20% in AD of corn straw. • The nZVI/PBC exhibited higher ability in maintaining the stability of AD system. Antibiotic mycelial residues (AMRs), as recyclable hazardous waste, can realize efficient utilization by reasonable treatment. To solve the problems of undeveloped pore structure and low specific surface area existed in AMR biochar, this study first modified biochar by phosphoric acid (H 3 PO 4) to prepare PBC (H 3 PO 4 -modified biochar). Then, PBC was used as carrier to load nano zero-valent iron (nZVI) for preparation of nZVI/PBC. Finally, the biochar materials were used to promote anaerobic digestion (AD) of corn straw. The results showed that H 3 PO 4 -modification can effectively improve the specific surface area, pore structure, and electron donating capacity of AMRs biochar. The using of PBC as carrier to load nZVI attenuated the agglomeration of nZVI particles. Both PBC and nZVI/PBC improved the AD process, with biogas yield enhanced by 29.63% and 29.26%, respectively. The nZVI/PBC exhibited higher ability in maintaining the stability of AD system and promotion of fiber degradation than PBC. [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]

• Biochar improved the efficiency of anaerobic digestion of antibiotic residues. • BC and nZVI-BC increased the gas production efficiency by 20.75% and 15.50%, respectively. • The effect of nZVI-BC was greater than BC in reducing ammonia nitrogen content. • nZVI-BC significantly enhanced the removal of aad A, ant (2″)-Ⅰ, qacEdelta 1 and sul 1. To address the problem of antibiotic mycelial dreg (AMD) treatment and removal of antibiotic resistance genes (ARGs), this study adopted anaerobic digestion (AD) technology, and added biochar (BC) and biochar loaded with nanosized zero-valent iron (nZVI-BC) to promote the AD of AMD and enhance the removal of ARGs. Results showed that nZVI-BC was better than BC in promoting AD due to the hydrogen evolution corrosion and the synergistic effect of nZVI and BC. In addition, BC and nZVI-BC can enhance the oxidative stress response and reduce ammonia stress phenomenon, which significantly reduces the abundance of aad A, ant(2″) -Ⅰ, qacEdelta 1 and sul 1. In conclusion, the enhance effect of nZVI-BC is greater than BC. The removal efficiency rates of nZVI-BC on the above-mentioned four ARGs were improved by 33%, 9%, 24% and 11%. [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]