Effects of exogenous N-acyl homoserine lactones (AHLs) on methanogenic activities and microbial community differences during anaerobic digestion.

N-acyl homoserine lactones (AHLs) function as signaling molecules influencing microbial community dynamics. This study investigates the impact of exogenously applied AHLs on methane production during waste-activated sludge (WAS) anaerobic digestion (AD). Nine AHL types, ranging from 10-4 to 10 µg/g VSS, were applied, comparing microbial community composition under optimal AHL concentrations. Firmicutes, Bacteroidetes, Chloroflexi, and Proteobacteria were identified in anaerobic digesters with C4-HSL, C6-HSL, and C8-HSL. Compared to the control, Halobacterota increased by 19.25%, 20.87%, and 9.33% with C7-HSL, C10-HSL, and C12-HSL. Exogenous C7-HSL enhanced the relative abundance of Methanosarcina, Romboutsia, Sedimentibacter, Proteiniclasticum, Christensenellaceae_R-7_group. C10-HSL increased Methanosarcina abundance. C4-HSL, C6-HSL, C8-HSL, C10-HSL, and C12-HSL showed potential to increase unclassified_Firmicutes. Functional Annotation of Prokaryotic Taxa (FAPROTAX) predicted AHLs' impact on related functional genes, providing insights into their role in AD methanogenesis regulation. This study aimed to enhance the understanding of the influence of different types of exogenous AHLs on AD and provide technical support for regulating the methanogenesis efficiency of AD by exogenous AHLs.

Enhancing volatile fatty acids production from waste activated sludge: The role of pretreatment by N,N-bis(carboxymethyl)-l-glutamate (GLDA).

N,N-bis(carboxymethyl)-l-glutamate (GLDA) is an eco-friendly chelating agent that effectively extracts multivalent metal ions from waste activated sludge (WAS) flocs, which could potentially alter their structure. However, the effect of GLDA on the production of volatile fatty acids (VFAs) from WAS is not well known. Here, we demonstrate that pretreatment with GLDA at a concentration of 200 mmol per kg VSS results in a significant increase of 142% in extractable extracellular polymeric substances and enhances the total VFAs yield by 64% compared to untreated samples. We reveal GLDA's capability to mobilize organic-binding multivalent metal ions within sludge flocs. Specifically, post-pretreatment analyses showed the release of 69.1 mg L-1 of Ca and 109.8 mg L-1 of Fe ions from the flocs, leading to a more relaxed floc structure and a reduced apparent activation energy (10.6 versus 20 kJ mol-1) for WAS solubilization. Molecular dynamic simulations further demonstrate GLDA's preferential binding to Fe3+ and Ca2+ over Mg2+. Our study suggests that GLDA pretreatment causes minimal disruption to reactor stability, thereby indicating the stability of microbial community composition. GLDA has emerged as a viable pretreatment agent for enhancing volatile fatty acids production from waste activated sludge.

Effect of zero-valent iron (ZVI) and biogas slurry reflux on methane production by anaerobic digestion of waste activated sludge.

This study aimed to improve anaerobic digestion (AD) efficiency through the addition of zero-valent iron (ZVI) and biogas slurry. This paper demonstrated that methane production was most effectively promoted at a biogas slurry reflux ratio of 60%. The introduction of ZVI into anaerobic systems does not enhance its bioavailability. However, both biogas slurry reflux and the combination of ZVI with biogas slurry reflux increase the relative abundance of microorganisms involved in the direct interspecific electron transfer (DIET) process. Among them, the dominant microorganisms Methanosaeta, Methanobacterium, Methanobrevibacter, and Methanolinea accounted for over 60% of the total methanogenic archaea. The Tax4Fun function prediction results indicate that biogas slurry reflux and the combination of ZVI with biogas slurry reflux can increase the content of key enzymes in the acetotrophic and hydrotrophic methanogenesis pathways, thereby strengthening these pathways. The corrosion of ZVI promotes hydrogen production, and the biogas slurry reflux provided additional alkaline and anaerobic microorganisms for the anaerobic system. Their synergistic effect promoted the growth of hydrotrophic methanogens and improved the activities of various enzymes in the hydrolysis and acidification phases, enhanced the system's buffer capacity, and prevented secondary environmental pollution. PRACTITIONER POINTS: Optimal methane production was achieved at a biogas slurry reflux ratio of 60%. Biogas slurry reflux in anaerobic digestion substantially reduced discharge. ZVI addition in combination with biogas slurry reflux facilitates the DIET process.

Metabolic profile of Phellodendron amurense Rupr. in vivo of rat and its metabolomic study on intervention in rheumatoid arthritis.

To analyze the metabolites (blood, urine and feces) in normal rats after intragastric administration of the decoction of Phellodendri Amurensis Cortex (PAC) and to map the metabolic profile of PAC in vivo of rat; meanwhile, to evaluate the anti-rheumatoid arthritis (RA) effect of PAC by blood metabolomics technique and to explore its mechanism. Performing on UPLC-Q-TOF-MS technology with a Waters ACQUITY UPLC BEH-C18 column (100 mm × 2.1 mm, 1.7 µm), the mobile phase was acetonitrile-0.1% formic acid aqueous solution (gradient elution). Prior to and following the administration of the decoction of PAC, the samples of blood, urine, and fecal were collected from the rats, in the positive ion mode, pharmacogenic metabolites in each biological sample were identified according to the accurate mass, fragment ions, retention time, metabolic reaction type, comparison of reference substance and retrieval of Pub Med database; The adjuvant-type arthritis (AA) rat model was established, and blood metabonomics method was used to study the improvement effect of rheumatoid arthritis after drug intervention with PAC, and its mechanism was preliminarily explored through analysis of metabolic pathway. A total of 72 exogenous components were identified, including 17 prototype components and 55 metabolites; 14 biomarkers were screened by blood metabolomics techniques combined with multivariate statistical analysis, and PAC significantly improved symptoms of rheumatoid arthritis in rats, and the metabolic pathway analysis mainly involves 5 metabolic pathways. The components in the aqueous decoction of PAC mainly undergo phase I metabolic reactions in rats, such as oxidation, reduction, dehydrogenation, demethylation, and phase II metabolic reactions, such as acetylation, glucuronidation, methylation; PAC has anti-rheumatoid arthritis effects, and its mechanism of action may be related to biosynthesis of aminoacyl-tRNA, metabolism of phenylalanine, metabolism of tryptophan, degradation of valine, leucine and isoleucine and biosynthesis of pantothenic acid and coenzyme A, providing a scientific basis for the study of the pharmacodynamic substances and the action mechanism of PAC against RA.