Food waste (FW) is a significant source of antibiotic resistance genes (ARGs) and anaerobic digestion is an effective strategy to limit the spread of antimicrobial resistance. In this study, ARGs diversity and abundance, along with their relationship to the microbial community were investigated by metagenomic and qPCR during thermophilic anaerobic co-digestion of FW, kitchen waste (KW) and garden waste (GW). Results indicate that R FK (FW + KW) and R FG (FW + GW) effectively reduced 9 and 13 representative ARG subtypes (removal rates exceeding 1 log unit), and completely eliminated 16 and 30 ARG subtypes, respectively, outperforming RF (FW). The Redundancy analysis indicated positive correlations between ARG removal rates and methane content, and negative correlations with volatile short-chain fatty acids and ammonia nitrogen. Procrustes and network centrality analyses suggested that removing resistant bacteria like Firmicutes and Bacteroidota in R FK and R FG contributed to efficient ARG removal. Co-digestion enhanced ARG elimination by improving reactor performance and altering bacterial communities.

Conventional mineralization of high-concentration organic pollutants relied on intensive chemicals and high carbon emissions, necessitating resource recovery strategies. We developed a high-energy electron beam (HEEB)-activated persulfate (PS) system, transforming 99 % of polyvinyl alcohol (PVA, 2 g/L) into recyclable precipitates with ultra-low PS dosage (0.1 g/L) and short irradiation duration (24 kGy, 38.4 s), along with 98 % chemical oxygen demand removal. Therein, radicals (SO4•- and •OH) were generated to induce PVA degraded into oligomers and repolymerized into particles, finally aggregating to form precipitates. The system demonstrated robust performance across wide ranges of pH (4-10) and PVA concentration (0.5-10 g/L), and complex matrices containing inorganic ions, dyes and benzene derivatives, highlighting its industrial applicability. Crucially, the precipitates exhibited versatile reuse potential as adhesives or flexible conductive materials, with lifecycle analysis confirming net-negative carbon emissions and economic viability. This study offered a sustainable wastewater remediation approach for transforming persistent organic pollutants into functional materials.

To overcome the limitations of denitrification under high dissolved oxygen conditions, an efficient aerobic denitrifier, Stutzerimonas stutzeri os3, was isolated from shrimp aquaculture sediment. The strain os3 achieved complete removal of nitrate without significant nitrite accumulation, when sodium citrate was used as the carbon source, with a C/N ratio of 5, and at a shaking speed of 50 r/min. Moreover, the strain os3 demonstrated a high TIN removal efficiency, reaching 98.29 % - 99.28 % under various nitrogen sources. Whole-genome sequencing revealed the presence of denitrification genes (napAB, nirS, norBC and nosZ) in the strain os3, which combined with nitrogen balance analysis, confirmed that the strain os3 primarily utilized aerobic denitrification for nitrate removal under aerobic conditions, as follows: NO- 3 - N -* the strain os3 significantly increased the removal efficiencies of TIN and NO3 --N in shrimp aquaculture wastewater, reaching 90.20 % and 94.43 %, respectively. Therefore, the strain os3 contributes to enhancing aerobic denitrification, providing a biotechnological solution for improving nitrogen cycling in shrimp aquaculture water.

Bioaugmentation for enhancing the performance of thermophilic anaerobic digestion (TAD) is attracting more focus. This study aimed to investigate the effect and mechanism of bioaugmentation with Caldibacillus thermoamylovorans QK5 on improving the methane production via TAD using food waste (FW). The results demonstrated that the inoculation of C. thermoamylovorans QK5 could increase the cumulative methane production from 380.33 NmL g-1 VS to 477.56 NmL g-1 VS, with an improvement of 25.57 %. Metagenomic analysis revealed that this effect was achieved by enhancing hydrolysis and acidification stages of TAD. The addition of C. thermoamylovorans QK5 effectively intensified the genes encoding key enzymes involved in the hydrolysis, acidification, and complete oxidation of carbohydrates, amino acids, and fatty acids into CO2, particularly various carbohydrate-active enzymes. Moreover, the C. thermoamylovorans QK5 can settle and reproduce in the TAD system, indicating that it is a reliable and effective strain for bioaugmentation of TAD from FW.

The phenomenon of Enteromorpha prolifera (EP) flooding caused by marine eutrophication has resulted in serious environmental impact. Here, we demonstrate an application of Fenton's reagent in the rapid recovery and utilization of EP. The humification of EP with water content of 80-90% is accelerated by adding H2O2 and FeSO4·7H2O. A notable self-heating phenomenon (from 22 to 86 °C) is observed within 10 min, and the sample is dried to obtain the EP fertilizer (EPF) after 60 min, which contained 25.5 ± 4.3% (wt%) of fulvic-like acid (FLA). Aromatization, amidation and carboxylation reactions induced by free radicals (mainly •OH) play a key role in EP (mainly polysaccharides and proteins) humification through degradation-polymerization pathway. A scale-up experiment is also carried out to confirm the feasibility of this technology. EPF increases the fresh weight of chickweeds (pot experiment) and cabbage (field plot experiment) by 27.1% and 609.7% compared with blank, respectively. This study opens a promising avenue for application of Fenton reaction in biowaste humification, which is beneficial for efficient EP recycling and agriculture sustainable development.

Dry anaerobic digestion (DAD) of kitchen waste (KW) has low methane production due to the poor mass transfer and the low abundance of functional microorganisms. This study employed multi-enzyme pretreatment (PRE), bioaugmentation with Paraclostridium benzoelyticum (BIO), and their combination (COM) to enhance methane production. Interestingly, the COM group had the highest methane production, which was increased by 18.51 %, 9.91 % and 12.39 % compared with the control, PRE and BIO groups, respectively, which indicated that there was a synergy between multi-enzyme pretreatment and bioaugmentation. Further analysis of microbial community and metagenome was conducted to reveal the synergistic mechanism. The results showed that in COM group, the enrichment of the Rikenellaceae, Methanobacteriaceae and Methanosaetaceae was the directly reason for enhancing methane production. Additionally, key metabolic functions including biosynthesis of cofactors, methane metabolism and oxidative phosphorylation also played a pivotal role in boosting methane production. Furthermore, the enhancement of the hydrogenotrophic methanogenesis pathway has been demonstrated to be a critical factor in the synergistic effects. It provided a reliable theoretical basis for the practical application of the multi-enzyme pretreatment combined with Paraclostridium benzoelyticum bioaugmentation for DAD.

To improve the cost-effectiveness of biobutanol production, lignocellulosic biomass is used as a cheap and sustainable feedstock. It provides fermentable sugars for microbial fermentation but lacks nitrogen resources and other nutrients. This study investigated the effects of combining multiple types of lignocellulosic biomass with nitrogen-rich wheat bran on ABE fermentation. Depending on the composition and fermentation effects, the optimal mixing ratio of wheat bran added with sugarcane bagasse, corncob and pine was 1:1, 1:4 and 2:3, respectively. The addition of corn steep powder as a nutritional source significantly enhanced sugar consumption and solvent concentration. Integration of pervaporation with ABE fermentation facilitated timely removal of butanol and alleviated product inhibition, resulting in a final total solvents concentration of 14.51 g/L, comparable to fermentation with TYA synthetic medium. This study demonstrates the feasibility of using combined lignocellulosic biomass to reduce feedstock costs and enhance the application of biobutanol production.

Microbial bioaugmentation is a promising strategy to increase methane production in thermophilic anaerobic digestion (TAD). In this study, Clostridium thermopalmarium HK1 and Caldibacillus thermoamylovorans QK5 were combined to form a combined microbial inoculant, and the influence of this synergistic bioaugmentation strategy on the TAD of food waste was explored in batch and semi-continuous experiments. The cumulative methane production reached 512.74 +/- 8.12 NmL g-1 VS with the addition of the combined microbial inoculant, which was increased by 24.77 % +/- 1.98 % compared to the control group, and the bioaugmentation effect was significantly better than that of the group inoculated with C. thermopalmarium HK1 (458.44 +/- 4.80 NmL g-1 VS, 11.56 % +/- 1.17 %) or C. thermoamylovorans QK5 (478.74 +/- 5.73 NmL g-1 VS, 16.50 % +/- 1.39 %) individually. The addition of the combined microbial inoculant particularly enriched carbohydrate-degrading bacteria and protein-degrading bacteria. In terms of metabolic functions, bioaugmentation with the combined microbial inoculant enhanced carbohydrate metabolism, amino acid metabolism, and methane metabolism, promoting the complete oxidation of organic matter into CO2 via the tricarboxylic acid cycle (TCA cycle) and driving the conversion of CO2 to methane. In particular, the synergistic effect of C. thermopalmarium HK1 and C. thermoamylovorans QK5 in the combined microbial inoculant resulted in notably increases in the bioaugmentation of carbohydrate and protein degradation, the TCA cycle, and hydrogenotrophic methanogenesis.

3-Fucosyllactose (3-FL) is an important oligosaccharide and nutrient in breast milk that can be synthesized in microbial cells by α-1,3-fucosyltransferase (α-1,3-FucT) using guanosine 5'-diphosphate (GDP)-l-fucose and lactose as substrates. However, the catalytic efficiency of known α-1,3-FucTs from various sources was limited due to their low solubility. To enhance the microbial production of 3-FL, the efficiencies of α-1,3-FucTs were evaluated and in Bacillus subtilis (B. subtilis) chassis cells that had been endowed with a heterologous synthetic pathway for GDP-l-fucose, revealing that the activity of FucTa from Helicobacter pylori (H. pylori) was higher than that of any of other reported homologues. To further improve the catalytic performance of FucTa, a rational design approach was employed, involving intracellular evaluation of the mutational sites of M32 obtained through directed evolution, analysis of the ligand binding site diversity, and protein structure simulation. Among the obtained variants, the FucTa-Y218 K variant exhibited the highest 3-FL yield, reaching 7.55 g/L in the shake flask growth experiment, which was 3.48-fold higher than that achieved by the wild-type enzyme. Subsequent fermentation optimization in a 5 L bioreactor resulted in a remarkable 3-FL production of 36.98 g/L, highlighting the great prospects of the designed enzyme and the strains for industrial applications.

Temperature is a crucial parameter for anaerobic digestion of food waste. Thermophilic anaerobic digestion (TAD) exhibits high methane production but has a hard initiation. This study compared two start-up strategies, one-step temperature increase and step-wise temperature increase, for achieving rapid TAD initiation. Compared to the step-wise temperature increase, the one-step temperature increase demonstrated stronger stability with slight pH fluctuation. Thermophilic communities were established more rapidly by the one-step temperature increase. Its substrate degradation was more enhanced through improving carbohydrates and lipid metabolisms than step-wise’s. These indicated one-step temperature increase strategy can initiate TAD efficiently. Additionally, a comparative analysis between TAD and mesophilic anaerobic digestion (MAD) was conducted on multilevels. TAD produced 25.29% more methane than MAD. The increased Defluviitoga and Hydrogenispora in TAD promoted hydrogenotrophic methanogenesis. The enriched genes related to the decomposition of glucose and glycerol resulted in higher substrate hydrolysis, acidogenesis, and acetogenesis in TAD than that in MAD. This study elucidated the full stages of TAD, which strengthened methanogenesis.

To effectively convert the fermentable sugars present in lignocellulosic biomass into biofuels and additional value-added products, it is crucial to remove lignin from the biomass. With the intention of expeditiously remove lignin from poplar wood and improve cellulose saccharification, an innovative ternary deep eutectic solvent (DES) benzyl triethyl ammonium chloride-ethylene glycol-FeCl3 (T-EG-F) was studied for the pretreatment of poplar hydrolyzed residue (PHR). The results revealed that following T-EG-F DES pretreatment at 130 °C for 4 h, the lignin removal rate reached 91.88 %. The effect of DES on PHR and regenerated lignin was comprehensively investigated using X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), Thermogravimetric (TG) and other characterization methods, providing valuable insights into the mechanism of this innovative biomass pretreatment. Moreover, there was a significant improvement in the enzyme digestibility of the DES pretreatment residue. At 48 h, the enzyme load of 30 FPU/g cellulose achieved a remarkable enzyme digestibility of 97.31 %, and this value exhibited a notable increase of 6.56 times compared to the untreated poplar sample. In addition, the T-EG-F could be recycled and reused. This study demonstrates that the potential of T-EG-F DES pretreatment as a green and efficient method for lignin dissociation from lignocellulosic biomass, offering a promising approach for biomass component separation.

2-Hydroxyisovalerate is a valuable chemical that can be used in the production of biodegradable polyesters. In nature, it was only produced at a very low level by Lactococcus lactis. 2-Ketoisovalerate is an intermediate metabolite of the branched-chain amino acid biosynthesis pathway, and Klebsiella pneumoniae ΔbudAΔldhA (Kp ΔbudAΔldhA) was a 2-ketoisovalerate producing strain. In this research, 2-hydroxyisovalerate was identified as a metabolite of Kp ΔbudAΔldhA, and its synthesis pathway was revealed. It was found that 2-ketoisovalerate and 2-hydroxyisovalerate were produced by Kp ΔbudA and Kp ΔbudAΔldhA, but not by Kp ΔbudAΔldhAΔilvD in which the 2-ketoisovalerate synthesis was blocked. budA, ldhA, and ilvD encode α-acetolactate decarboxylase, lactate dehydrogenase, and dihydroxy acid dehydratase, respectively. Thus, it was deduced that 2-hydroxyisovalerate was synthesized from 2-ketoisovalerate. Isoenzymes of ketopantoate reductase PanE, PanE2, and IlvC were suspected of being responsible for this reaction. Kinetic parameters of these enzymes were detected, and they all hold the 2-ketoisovalerate reductase activities. PanE and PanE2 use both NADH and NADPH as co-factors. While IlvC only uses NADH as a co-factor. Over-expression of panE, panE2, or ilvC in Kp ΔbudAΔldhA all enhanced the production of 2-hydroxyisovalerate. Accordingly, 2-hydroxyisovalerate levels were reduced by knocking out panE or panE2. In fed-batch fermentation, 14.41 g/L of 2-hydroxyisovalerate was produced by Kp ΔbudAΔldhA-panE, with a substrate conversion ratio of 0.13 g/g glucose.

For better understanding the mechanism of microbial strains promoting methane production, four strains Hungatella xylanolytica A5, Bacillus licheniformis B1, Paraclostridium benzoelyticum C2 and Advenella faeciporci E1 were inoculated into anaerobic digestion systems. After bioaugmentation, the cumulative methane production of A5, B1, C2 and E1 groups elevated by 11.68%, 8.20%, 18.21% and 15.67% compared to CK group, respectively. The metagenomic analysis revealed that the species diversity and uniformity of the experimental groups was improved, and hydrolytic acidifying bacteria, represented by Clostridiaceae, Anaerolineaceae and Oscillospiraceae, and methanogens, such as Methanotrichaceae and Methanobacteriaceae, were enriched. Meanwhile, the abundance of key genes in carbohydrate, pyruvate and methane metabolism was increased in the inoculated groups, providing reasonable reasons for more methane production. The strengthening mechanism of microbial strains in this study offered a theoretical foundation for selecting a suitable bioaugmentation strategy to solve the problems of slow start-up and low methane production in anaerobic digestion.

Caragana korshinskii kom. (CKK) waste, a common forestry byproduct in northwest of China, presents challenges in its transformation into alternative ruminant feed due to its initial nutritional limitations and unappealing palatability. Conventional strategies, such as ensiling and fungal-based solid-state fermentation (SSF) cannot effectively address this issue in practice. Herein, a two-stage bioaugmentation (TBA) process was devised, leveraging the benefits of ensiling and SSF. During the anaerobic ensiling phase, CKK waste was inoculated with Lactiplantibacillus plantarum LP1, effectively suppressing potential animal pathogens such as Aspergillus and Nocardiopsis while enriching the material with potential probiotics like Pediococcus and Lactiplantibacillus, reaching an abundance of 95.7%. In the subsequent aerobic SSF stage, the ensiled CKK underwent inoculation with the white-rot fungus Irpex lacteus F17, which became enriched to 87.9%. Comprehensive multi-omics analysis identified Irpex as the key taxon, possessing an extensive redox enzyme system that led to the improvement in nutrient composition, reduction of astringent phenolic substances, and mitigation of mycotoxins. As a result, the crude protein content of the CKK increased by 39.2%, while lignin, total phenolic substances, and tannic acid content decreased by 24.4%, 52.2%, and 51.4%, respectively. The mycotoxin levels, including aflatoxin B1, zearalenone, and vomitoxin, were rendered negligible, confirming the safety. Overall, this study demonstrates the TBA strategy can successfully transform challenging and unpalatable CKK waste into a nutrient-enriched and safe mycelium-based bioproduct, thereby enabling the valorization of a previously underutilized forestry resource as a promising alternative feed.

The high moisture content of kitchen waste (KW) restricts the future treatment and resource utilization. Biodrying is an effective approach to remove the water of KW. However, conventional biodrying only uses the heat generated by the indigenous microorganisms to remove water, which has long treatment cycle and low moisture removal rate. Microbial bioaugmentation is an emerging approach to improve the biodrying efficiency of KW. In this study, a thermophilic bacterial agent (TBA) composed of Bacillus, Geobacillus and Acinetobacter was used to promote water evaporation during the biodrying process. Based on the results, the moisture removal rate of experimental group inoculated with TBA was 82.20 %, which was notably higher than CK group without inoculation. Moreover, TBA significantly increased the amount of organic matter degradation. Microbial community analysis revealed that TBA could promote the proliferation of thermophilic bacteria and make bacterial community more tolerant to high temperature environment. Further analysis of metabolic pathways showed that quorum sensing and glyoxylate and dicarboxylate metabolism were enhanced by TBA inoculation, which can help microorganisms to better adapt to high temperature environment and release more energy to facilitate the water evaporation. This study offers a fresh approach to improve the water removal efficiency in biodrying process.

To enhance methane production and ensure system stability in the thermophilic anaerobic digestion (TAD) of food waste (FW), bioaugmentation is a straightforward and effective strategy. This study investigated the bioaugmentation effect of Clostridium thermopalmarium HK1 on the TAD of FW. The results showed that the cumulative methane production (CMP) and the average methane content after bioaugmentation increased by 23.67% and 22.69%, respectively. Moreover, the addition of C. thermopalmarium HK1 contributed to alleviating ammonia inhibition and promoting volatile fatty acids (VFAs) conversion, thus maintaining the system stability. The dominant hydrolytic bacteria and hydrogenotrophic methanogens were enriched in the early stage after bioaugmentation. The genus Clostridium was positively correlated with methane content. Metagenomic analysis further suggested that methane metabolism was strengthened, and the relative abundances of genes encoding the key functional enzymes associated with hydrogenotrophic and acetoclastic methanogenic pathways were enhanced. Therefore, bioaugmentation with C. thermopalmarium HK1 had great potential for improving the efficiency of the TAD of FW.

The objective of this study was to investigate the impact of thermophilic bacteria on crude fiber content, carbohydrate-active enzyme (CAZyme) genes, and associated microbial communities during Chinese medicine residues composting. The study examines changes over 15 days of composting with (T) and without (CK) thermophilic microbial agents. Results show that the group T compost temperature reached a maximum of 71.0 °C and remained above 70 °C for 2 days, while the group CK maximum temperature was only 60.9 °C. On Day 15, the seed germination index (GI) of group T reached 98.7%, while the group CK GI was only 56.7%. After composting, the degradation rates of cellulose, hemicellulose, and lignin in group T increased by 5.1, 22.5, and 18.5%, respectively, compared to those in group CK. Thermophilic microbial agents changed the microbial communities related to CAZymes, increasing unclassified_o_Myxococcales and Sphaerobacter abundance and reducing Acinetobacter and Sphingobacterium abundance. Thermophilic microbial agents also increased the abundance of the GT4, GT2_Glycos_transf_2, and AA3 gene families. These results show that thermophilic microbial agents can increase composting temperature, accelerate compost maturation, and promote crude fiber degradation. Therefore, they have broad application potential.

Acyl-CoA dehydrogenase (ChsE) is involved in the steroid side-chain degradation process. However, their function in vivo remains unclear. In this study, three ChsE, ChsE1-ChsE2, ChsE3, and ChsE4-ChsE5, were identified in Mycolicibacterium neoaurum, and their functions in vivo are studied and compared with those from Mycobacterium tuberculosis in vitro. By gene knockout, complementation, and the bioconversion of phytosterols, the function of ChsE was elucidated that ChsE4-ChsE5 could utilize C27, C24, and C22 steroids in vivo. ChsE3 could utilize C27 and C24 steroids in vivo. ChsE1-ChsE2 could utilize C27, C24, and C22 steroids in vivo. What is more, the production strain of a C22 steroid, 3-oxo-4,17-pregadiene-20-carboxylic acid methyl ester (PDCE), is constructed with ChsE overexpression. This study improved the understanding of the steroid bioconversion pathway and proposed a method of the production of a new C22 steroid. KEY POINTS: • Three ChsE paralogs from M. neoaurum are identified and studied. • The function of ChsE is overlapped in vivo. • A C22 steroid (PDCE) producer was constructed with ChsE overexpression.

Food waste (FW) single-substrate anaerobic digestion usually suffers from rapid acidification and inhibition of oil and salt. To overcome these problems and improve the process efficiency, supplementing other substrates has been used in FW anaerobic digestion. This study investigated the biogas production potential through co-digestion of FW with kitchen waste (KW) or garden waste (GW) in different ratios under thermophilic conditions. The results showed that the optimal ratios were FW:KW=60:40 and FW:GW=80:20 which biogas production improved 73.33% and 68.45% compared with single FW digestion, respectively. The organic matter removal rate of co-digestion was 84.46% for FW+KW group (RFK) and 65.64% for FW+GW group (RFG). Co-digestion increased the abundance of the dominant hydrolytic bacteria Defluviitoga and Hydrogenispora and hydrogenotrophic methanogen Methanoculleus. Furthermore, glycoside hydrolases (GHs), vital carbohydrate-active enzymes (CAZymes), were improved by co-digestion. Co-digestion could also effectively promote the function of cellulase and hemicellulose. This strategy for utilizing different organic wastes together as co-substrate provides a new avenue for bioenergy production.

Bioaugmentation technology for improving the performance of thermophilic anaerobic digestion (TAD) of food waste (FW) treatment is gaining more attention. In this study, four thermophilic strains (Ureibacillus suwonensis E11, Clostridium thermopalmarium HK1, Bacillus thermoamylovorans Y25 and Caldibacillus thermoamylovorans QK5) were inoculated in the TAD of FW system, and the biochemical methane potential (BMP) batch study was conducted to assess the potential of different bioaugmented strains to enhance methane production. The results showed that the cumulative methane production in groups inoculated with E11, HK1, Y25 and QK5 improved by 2.05%, 14.54%, 19.79% and 9.17%, respectively, compared with the control group with no inoculation. Moreover, microbial community composition analysis indicated that the relative abundance of the main hydrolytic bacteria and/or methanogenic archaea was increased after bioaugmentation, and the four strains successfully became representative bacterial biomarkers in each group. The four strains enhanced methane production by strengthening starch, sucrose, galactose, pyruvate and methane metabolism functions. Further, the correlation networks demonstrated that the representative bacterial genera had positive correlations with the differential metabolic functions in each bioaugmentation group. This study provides new insights into the TAD of FW with bioaugmented strains.