Clostridium cluster I and their pathogenic members in a full-scale operating biogas plant

Microbial β-oxidation of synthetic long-chain fatty acids to improve lipid biomethanation

β-oxidation is a well-known pathway for fatty acid (FA) degradation. However, the wide range of feedstocks, their intermediates, and complex microbial networks involved in anaerobic digestion (AD) make β-oxidation unclear during lipid digestion having a variety of long-chain fatty acids (LCFAs). Here, we demonstrated the detailed metabolic pathway of major bacteria and enzymes responsible for the β-oxidation of individual saturated FAs (C16:0 and C18:0) and unsaturated FAs (C18:1 and C18:2). C16:0 showed no negative impact on AD. The relative enzyme abundance and production of shorter-chain FAs ( Collapse

Key Words

• Biomethanation
• Community response
• Saturated fatty acids
• Unsaturated fatty acids
• Β-oxidation

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Affiliation(s)

Muhammad Usman MOE, Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, Gansu, China; Department of Occupational and Environmental Health, School of Public Health, Lanzhou University Lanzhou 730000, Gansu, China
Shuai Zhao MOE, Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, Gansu, China
Byong-Hun Jeon Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Korea
El-Sayed Salama Department of Occupational and Environmental Health, School of Public Health, Lanzhou University Lanzhou 730000, Gansu, China.
Xiangkai Li MOE, Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, Gansu, China.

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Enhanced degradation of glucocorticoids, a potential COVID-19 remedy, by co-fermentation of waste activated sludge and animal manure: The role of manure type and degradation mechanism

Waste activated sludge (WAS) and animal manure are two significant reservoirs of glucocorticoids (GCs) in the environment. However, GC degradation during anaerobic digestion (AD) of WAS or animal manure has rarely been investigated. In this study, co-fermentation of WAS and animal manure was conducted to investigate the performance of AD in controlling GC dissemination. Effects of manure type on GC degradation and sludge acidification were investigated. The results showed that co-fermentation of WAS and chicken manure (CM) significantly enhanced the degradation of hydrocortisone (HC) to 99%, betamethasone (BT) to 99%, fluocinolone acetonide (FA) to 98%, and clobetasol propionate (CP) to 82% in 5 days with a mixing ratio of 1:1 (g TS sludge/g dw manure) at 55 °C and initial pH of 7. Simultaneously, sludge reduction was increased by 30% and value-added volatile fatty acid (VFA) production was improved by 40%. Even a high GC content of biomass (3.6 mg/g TS) did not impact both sludge hydrolysis and acidification. The amendment of WAS with CM increased soluble organic carbon, Ca²⁺, and relative abundance of anaerobes (Eubacterium) associated with organic compound degradation. Furthermore, 44 transformation products of HC, BT, FA, and CP with lower lipophilicity and toxicity were identified, indicating possible degradation pathways including hydroxylation, ketonization, ring cleavage, defluorination, hydrogenation, methylation, and de-esterification. Overall, this study provides a practical way to control GC pollution and simultaneously promote waste reduction and VFA production. Animal manure type as an overlooked factor for influencing co-fermentation performance and pollutant degradation was also highlighted.

In Vitro Evaluation of the Effects of Tylosin on the Composition and Metabolism of Canine Fecal Microbiota

Simple Summary

The antibiotic-responsive enteropathy is a common canine chronic disorder for which tylosin represents an effective widely used therapeutic option, although its mechanism of action, beyond the well-known antibacterial activity, is still unclear. Given the beneficial role of prebiotic substrates for gut health, positive outcomes deriving from the association of tylosin with some prebiotic oligosaccharides might be supposed. The present study investigated in vitro the effects of tylosin, alone or supplemented with fructooligosaccharides, galactooligosaccharides, or xylooligosaccharides, on the composition and activity of the fecal microbiota of healthy dogs. It was partially confirmed that the antibacterial effect of tylosin, given the reduction of some microbial populations and metabolites, e.g., volatile fatty acids. Interestingly, the association of tylosin with prebiotics revealed counteracting effects on some undesirable changes exerted by tylosin, e.g., the reduction of bacteria generally considered beneficial such as lactobacilli and Clostridium cluster XIVa as well as volatile fatty acids, i.e., microbial fermentative end-products that are recognized as essential for enterocytes homeostasis.

Abstract

The present study investigated the in vitro effects of tylosin (TYL), alone or associated with prebiotics (PRE), on selected canine fecal parameters. Eight treatments were set up: control diet with no addition of substrates; TYL; Fructooligosaccharides (FOS); Galactooligosaccharides (GOS); Xylooligosaccharides (XOS); TYL + FOS; TYL + GOS; TYL + XOS. The flasks (five for treatment), containing a canine fecal suspension (prepared with the feces of healthy adult dogs) and the residue of an in vitro digested dry dog food, were incubated in an anaerobic chamber at 39 °C. TYL and PRE were added at a concentration of 0.2 and 1 g/L, respectively. Samples were collected after 6 and 24 h for analyses. PRE decreased pH values, iso-butyrate, and iso-valerate throughout the incubation; increased lactobacilli, cadaverine, and, tendentiously, total volatile fatty acids after 6 h; increased n-butyrate, putrescine, spermidine, and reduced spermine and E. coli after 24 h. TYL resulted in lower total volatile fatty acids and lactobacilli and higher Clostridium cluster I after 6 h and higher pH values, spermidine, and E. coli throughout the study. When associated with TYL, PRE counteracted some undesirable effects of the antibiotic such as the decrease of lactobacilli and Clostridium cluster XIVa at both 6 and 24 h. In the present study, TYL exhibited inhibitory effects on canine fecal microbiota partially counteracted by PRE supplementation.

Sulforaphane Normalizes Intestinal Flora and Enhances Gut Barrier in Mice with BBN-Induced Bladder Cancer

SCOPE

Gut microbiota imbalance, inflammation, and gut barrier deficiency play an important role in carcinogenesis. Sulforaphane (SFN), an isothiocyanate found in cruciferous vegetables, has been proven to be highly effective in inhibiting cancer. The objective of this study is to investigate the potential roles of the gut microbiota in the inhibition of BBN-induced bladder cancer by SFN.

METHODS AND RESULTS

N-butyl-N-(4-hydroxybutyl)-nitrosamine is used to induce bladder cancer in male C57BL/6 mice, with or without SFN for 23 weeks. SFN ameliorates the histological changes characteristic of bladder cancer, resulting in fewer submucosal capillaries. SFN normalizes gut microbiota dysbiosis in mice with BBN-induced bladder cancer with a significant increase in Bacteroides fragilis and Clostridium cluster I. SFN also increases butyric acid levels in the mouse colon, and repairs the injury to the mucosal epithelium of the colon and cecum through the upregulation of the expression of tight junction proteins and GLP2. SFN greatly decreases the release of cytokines (IL-6) and secretory immunoglobulin A in the mice with bladder cancer.

CONCLUSION

These results suggest that SFN protects against chemical-induced bladder cancer through normalizing the composition of gut microbiota and repairing the physiological destruction of the gut barrier, as well as decreasing inflammation and the immune response.

Biochemical Conversion and Microbial Community in Response to Ternary pH Buffer System during Anaerobic Digestion of Swine Manure

The ternary pH buffer system with ammonia-carbonates-volatile fatty acids (VFAs) is essential to anaerobes for bioenergy recovery via anaerobic digestion (AD). However, ammonia and VFAs are recognized as potential inhibitors that depress methanogenesis. In this study, biochemical conversion and the microbial community in batch AD at total solid (TS) from 4% to 14% were investigated to reveal their response to the ternary pH buffer system. The rapid ammonia release, probably promoted by Anaerosphaera and Eubacterium inferred from the concurrent peak of their relative abundance, triggered total ammonia (TAN) inhibition with the accumulation of VFAs in the start-up stage of high solid AD (HSAD, TS ≥ 8%). Along with evolution of the microbial community to resist high TAN and VFAs, methanogenesis recovered with improved degradation of VFAs and reduction of COD. When exposed to 3500 mg·N·L−1 TAN at 8% TS, aceticlastic Methanosarcina became dominant first and then together with hydrogenotrophic Methanoculleus, achieved the optimal biochemical conversion. While in HSAD at 11–14% TS, the main pathway of methanogenesis appeared to have shifted from the aceticlastic pathway to the hydrogenotrophic pathway, as inferred by changes in the relative abundance of methanogens, and this could have been induced by the increasing concentration of high free ammonia (FAN, ≥588 mg·N·L−1). Although the anaerobes had acclimatized to high TAN, the propionate-oxidizing bacteria and acetate-oxidizing bacteria might have again been inhibited by high FAN, frustrating the H2 supply for FAN-tolerant Methanoculleus and causing an 8.2–11.3% depression of COD reduction (mainly propionate residual).