Generation Of Short-chain Fatty Acids Research Articles

High-fiber diets attenuate emphysema development via modulation of gut microbiota and metabolism

Dietary fiber functions as a prebiotic to determine the gut microbe composition. The gut microbiota influences the metabolic functions and immune responses in human health. The gut microbiota and metabolites produced by various dietary components not only modulate immunity but also impact various organs. Although recent findings have suggested that microbial dysbiosis is associated with several respiratory diseases, including asthma, cystic fibrosis, and allergy, the role of microbiota and metabolites produced by dietary nutrients with respect to pulmonary disease remains unclear. Therefore, we explored whether the gut microbiota and metabolites produced by dietary fiber components could influence a cigarette smoking (CS)-exposed emphysema model. In this study, it was demonstrated that a high-fiber diet including non-fermentable cellulose and fermentable pectin attenuated the pathological changes associated with emphysema progression and the inflammatory response in CS-exposed emphysema mice. Moreover, we observed that different types of dietary fiber could modulate the diversity of gut microbiota and differentially impacted anabolism including the generation of short-chain fatty acids, bile acids, and sphingolipids. Overall, the results of this study indicate that high-fiber diets play a beneficial role in the gut microbiota-metabolite modulation and substantially affect CS-exposed emphysema mice. Furthermore, this study suggests the therapeutic potential of gut microbiota and metabolites from a high-fiber diet in emphysema via local and systemic inflammation inhibition, which may be useful in the development of a new COPD treatment plan.

Porphyromonas gingivalis Produce Neutrophil Specific Chemoattractants Including Short Chain Fatty Acids.

Neutrophil migration from blood to tissue-residing microbes is governed by a series of chemoattractant gradients of both endogenous and microbial origin. Periodontal disease is characterized by neutrophil accumulation in the gingival pocket, recruited by the subgingival biofilm consisting mainly of gram-negative, anaerobic and proteolytic species such as Porphyromonas gingivalis. The fact that neutrophils are the dominating cell type in the gingival pocket suggests that neutrophil-specific chemoattractants are released by subgingival bacteria, but characterization of chemoattractants released by subgingival biofilm species remains incomplete. In the present study we characterized small (< 3 kDa) soluble chemoattractants released by growing P. gingivalis, and show that these are selective for neutrophils. Most neutrophil chemoattractant receptors are expressed also by mononuclear phagocytes, the free fatty acid receptor 2 (FFAR2) being an exception. In agreement with the selective neutrophil recruitment, the chemotactic activity found in P. gingivalis supernatants was mediated in part by a mixture of short chain fatty acids (SCFAs) that are recognized by FFAR2, and other leukocytes (including monocytes) did not respond to SCFA stimulation. Although SCFAs, produced by bacterial fermentation of dietary fiber in the gut, has previously been shown to utilize FFAR2, our data demonstrate that the pronounced proteolytic metabolism employed by P. gingivalis (and likely also other subgingival biofilm bacteria associated with periodontal diseases) may result in the generation of SCFAs that attract neutrophils to the gingival pocket. This finding highlights the interaction between SCFAs and FFAR2 in the context of P. gingivalis colonization during periodontal disease, but may also have implications for other inflammatory pathologies involving proteolytic bacteria.

Alkaline environments benefit microbial K-strategists to efficiently utilize protein substrate and promote valorization of protein waste into short-chain fatty acids

Anaerobic bioconversion of protein into short-chain fatty acids (SCFAs) can help reduce the vast quantities of protein waste generated currently and provide precursors for biorefineries of value-added, renewable chemicals or fuels. However, low yields of SCFAs during this process have limited its application, since the underlying mechanism is not fully understood. Herein, we investigated the chemical and microbiological mechanisms of a combined heat-alkaline pretreatment and anaerobic alkaline fermentation scheme for protein conversion to SCFAs. A series of chemical analyses indicated that heat-alkaline pretreatment fragmented native proteins and induced protein unfolding, thus increasing the amount of readily biodegradable proteins. Further, microbial characterization, using the r-K life history theory, indicated that microbial K-strategists, such as Proteobacteria, have adapted to the alkaline fermentation environment and enriched the process of converting protein substrates, which corresponded to an improved acetate production. We also evaluated the technological and economic feasibility of utilizing Proteiniphilum acetatigenes to augment the process of SCFA generation from sewage sludge (a protein-rich waste). Our findings demonstrated the influence of chemical and biological process manipulations on microbial assembly structures and ecological strategies, supporting the further development of waste-to-profit technologies.

Mechanisms of potassium permanganate pretreatment improving anaerobic fermentation performance of waste activated sludge

Potassium permanganate (KMnO4), one typical strong oxidant, is used extensively in various applications. However, its impact on anaerobic fermentation of waste activated sludge is unknown. This paper therefore aims to investigate its effect on generation of short-chain fatty acids (SCFAs) and qualities of fermentation liquor and fermented solid sludge. Experimental results showed that when KMnO4 increased from 0 to 0.1 g/TSS, the highest SCFAs production enhanced from 33.9 to 251.8 mg COD/g VSS. The mechanism analysis revealed that KMnO4 addition increased the disintegration of sludge cells and the degradation of substantial recalcitrant organics in sludge such as humus and lignocellulose, thereby provided more substances for SCFAs generation. Ultraviolet absorption spectroscopy analysis showed that KMnO4 addition destroyed unsaturated conjugated bonds and decreased organics aromaticity, thereby promoting humus and lignocellulose degradation. GC/MS analyses showed that several micro-molecular substances (e.g., acid-like, alkane-like, and alcohol-like organics) were generated from KMnO4 pretreated humus and lignocellulose, and some of them were demonstrated to serve as substrates to produce SCFAs. The enzyme activity and model-based analyses showed that although KMnO4 restrained all the microorganisms to some extends, the activities of SCFAs generators were much higher than those of SCFAs consumers. In addition, the sludge mixture was separated into liquid and solid fraction after anaerobic fermentation, and the components in fermentation liquid and solid sludge were tested. It was found that the addition of KMnO4 effectively reduced the categories and total detected frequency of refractory organic pollutants in fermentation liquid, which improved the quality of the produced SCFAs. KMnO4 addition also increased the inactivation of fecal coliforms and degradation of emerging contaminants in fermented sludge, which were helpful to its final disposal.

Long-Term Consumption of 2-O-β-d-Glucopyranosyl-l-ascorbic Acid from the Fruits of Lycium barbarum Modulates Gut Microbiota in C57BL/6 Mice.

The modulating effect of 2-O-β-d-glucopyranosyl-l-ascorbic acid (AA-2βG), a natural derivative of ascorbic acid from the fruits of Lycium barbarum, on mice gut microbiota was investigated in the present study. It was found that AA-2βG was able to adjust the structure of mice gut microbiota, elevated the relative abundances of Verrucomicrobia, Porphyromonadaceae, Verrucomicrobiaceae, and Erysipelotrichaceae, and meanwhile reduced the relative abundances of Firmicutes, Lachnospiraceae, Rikenellaceae, Ruminococcaceae, Bdellovibrionaceae, Anaeroplasmataceae, and Peptococcaceae. Through the linear discriminant analysis effect size analysis, the key microbiota that were found to be significantly changed after long-term consumption of AA-2βG were Ruminococcaceae, Porphyromonadaceae, Lachnospiraceae, and Rikenellaceae. In addition, AA-2βG could upregulate pro-inflammatory cytokines, promote tight junctions between intestinal cells, facilitate the generation of short-chain fatty acids (SCFAs), and upregulate the mRNA expression level of SCFAs receptors, indicating that AA-2βG might promote organism health. The results demonstrated that AA-2βG might maintain organism health by modulating gut microbiota.

Astragaloside IV alleviates mouse slow transit constipation by modulating gut microbiota profile and promoting butyric acid generation.

Gut microbiota and short‐chain fatty acids (SCFAs) are associated with the development of various human diseases. In this study, we examined the role of astragaloside IV in modulating mouse gut microbiota structure and the generation of SCFAs, as well as in slow transit constipation (STC). An STC model was established by treating mice with loperamide, in which the therapeutic effects of astragaloside IV were evaluated. The microbiota community structure and SCFA content were analysed by 16S rRNA gene sequencing and gas chromatography‐mass spectrometry, respectively. The influence of butyrate on STC was assessed using a mouse model and Cajal cells (ICC). Astragaloside IV promoted defecation, improved intestinal mobility, suppressed ICC loss and alleviated colonic lesions in STC mice. Alterations in gut microbiota community structure in STC mice, such as decreased Lactobacillus reuteri diversity, were improved following astragaloside IV treatment. Moreover, astragaloside IV up‐regulated butyric acid and valeric acid, but decreased isovaleric acid, in STC mouse stools. Butyrate promoted defecation, improved intestinal mobility, and enhanced ICC proliferation by regulating the AKT–NF‐κB signalling pathway. Astragaloside IV promoted intestinal transit in STC mice and inhibited ICC loss by regulating the gut microbiota community structure and generating butyric acid.

New insight into waste activated sludge acetogenesis triggered by coupling sulfite/ferrate oxidation with sulfate reduction-mediated syntrophic consortia

Acetate (HAc) production via acetogenesis is a promising biorefinery approach for waste activated sludge (WAS); however, it is hampered by the thermodynamic constraints of the bioconversion of 3–5 carbon atom short-chain fatty acids (SCFAs). Sulfate radical (SO4∙‾)-based advanced oxidation is regarded as an appropriate candidate for accelerating WAS fermentation. In this study, we enriched an incomplete-oxidative sulfate reducing bacteria (io-SRB), combined with SO4∙‾ oxidation (generated by potassium ferrate (PF) and sodium sulfite (Na2SO3)), to boost WAS acetogenesis. Generated sulfate during SO4∙‾ oxidation served as the necessary substrates for io-SRB metabolism. A proof-of-concept based on experimental data for the whole process is presented. Results confirmed that the PF + Na2SO3 + SRB test achieved the maximum SCFAs generation (4261 ± 210 mg COD/L with 60.9 ± 0.5% HAc) over the PF + Na2SO3 test without io-SRB mediation (2521 ± 109 mg COD/L with 50.6 ± 0.3% HAc). Particle size analysis and fluorescence spectroscopy indicated that PF + Na2SO3 oxidation had positive effects on accelerating soluble organics release. SO4∙‾ was the key radical, playing the most important role, as indicated by electron paramagnetic resonance and radical scavenging analysis. X-ray photoelectron spectroscopy revealed that io-SRB mediation further promoted the transformation of polysaccharides and proteins into carboxylic acids, based on SO4∙‾ oxidation. Moreover, 79% Fe(VI) was reduced to Fe(III), and most S(IV) was converted to SO42−, approximately 40% of which was metabolized by io-SRB consortium. Clearly, SO4∙‾ oxidation and io-SRB stimulation significantly altered the composition of the key microbiome, with fermentative acidogenic bacteria predominating. The possible synergistic relationships among io-SRB, hydrolyzing bacteria and acidogens were revealed by molecular ecological network analysis. This study provides new insights into the improvement of value-added bio-metabolite recovery from SO4∙−-based WAS fermentation.

Gastrointestinal Inflammation and the Gut Microbiome: An Evolving Conceptual Framework with Implications for Diagnosis and Therapy in Inflammatory Bowel Disorders

The human gut microbiome has garnered much attention over the past two decades with important discoveries linking it to human health and disease. The commensal bacterial flora evolves due to the influence of a number of factors including diet, pathogen exposure, environmental toxicants, disease states, and a challenged microenvironment that requires balancing with the host itself. However, the composition of bacterial species can impact and contribute to the development of local and systemic inflammation. Among the factors attributed to intestinal inflammation are dysbiosis caused by pathogenic bacteria, following decreased host immunity or loss of intestinal barrier function. Dysbiosis can also be triggered by antibiotic therapy or the use of other medications that allow for colonisation of pathogenic bacteria, such as proton pump inhibitors. The imbalance with commensal bacteria leads to the generation of proinflammatory mediators and a reduction of host immune defences, due to a lack of short-chain fatty acid generation needed for energy production to maintain barrier and immune function. The initially localised inflammation results in further dysbiosis as former commensal bacteria are able to breach the barrier and cause systemic immune responses. Low-grade systemic inflammation is a hallmark of inflammatory bowel disease. Because a specific dysbiosis is common in patients with inflammatory bowel disease, it can serve as an early diagnostic marker in its development. Furthermore, faecal microbiome transplants have shown promising benefits in patients with ulcerative colitis and Crohn’s disease.

Antihyperlipidaemic effect of microencapsulated Lactobacillus plantarum LIP-1 on hyperlipidaemic rats.

Previous studies have shown that Lactobacillus plantarum LIP-1 (hereafter LIP-1) has an obvious hypolipidemic effect, and microencapsulated probiotics can ensure the strains live through the gastrointestinal tract. Although there has been much research on both preparation and assessment methods for probiotics microcapsules, most assessments were made in vitro and few were validated in vivo. In this study, the protective effect of microencapsulation and the possible hypolipidemic mechanisms of probiotic LIP-1 were evaluated in rats. Treatments included rats fed on a normal diet, a high-fat diet, and a high-fat diet with an intragastric supplement of either non-microencapsulated LIP-1 cells (NME LIP-1) or microencapsulated LIP-1 (ME LIP-1). Lipid metabolism indicators were measured during the experiment and following euthanasia. Microencapsulation increased survival and colonization of LIP-1 in the colon. ME LIP-1 was superior to NME LIP-1 in reducing cholesterol. The mechanisms behind the hypolipidemic effect exerted by LIP-1 are possibly due to promoting the excretion of cholesterol, improving antioxygenic potentials, enhancing recovery from the injury in the liver, cardiovascular intima and intestinal mucosa, promoting the generation of short-chain fatty acids, and improving lipid metabolism. This study confirms that microencapsulation provides effective protection of LIP-1 in the digestive system and the role of LIP-1 in the prevention and cure of hyperlipidaemia, providing theoretical support for probiotics to enter clinical applications. © 2019 Society of Chemical Industry.

Prebiotics and the poultry gastrointestinal tract microbiome

Feed additives that can modulate the poultry gastrointestinal tract and provide benefit to bird performance and health have recently received more interest for commercial applications. Such feed supplements offer an economic advantage because they may directly benefit poultry producers by either decreasing mortality rates of farm animals, increasing bird growth rates, or improve feed efficieny. They can also limit foodborne pathogen establishment in bird flocks by modifying the gastrointestinal microbial population. Prebiotics are known as non-digestible carbohydrates that selectively stimulate the growth of beneficial bacteria, thus improving the overall health of the host. Once prebiotics are introduced to the host, 2 major modes of action can potentially occur. Initially, the corresponding prebiotic reaches the intestine of the chicken without being digested in the upper part of the gastrointestinal tract but are selectively utilized by certain bacteria considered beneficial to the host. Secondly, other gut activities occur due to the presence of the prebiotic, including generation of short-chain fatty acids and lactic acid as microbial fermentation products, a decreased rate of pathogen colonization, and potential bird health benefits. In the current review, the effect of prebiotics on the gastrointestinal tract microbiome will be discussed as well as future directions for further research.

Gut microbiota in non-alcoholic fatty liver disease and alcohol-related liver disease: Current concepts and perspectives.

The term, gut-liver axis, is used to highlight the close anatomical and functional relationship between the intestine and the liver. It has been increasingly recognized that the gut-liver axis plays an essential role in the development and progression of liver disease. In particular, in non-alcoholic fatty liver disease and alcohol-related liver disease, the two most common causes of chronic liver disease, a dysbiotic gut microbiota can influence intestinal permeability, allowing some pathogens or bacteria-derived factors from the gut reaching the liver through the enterohepatic circulation contributing to liver injury, steatohepatitis, and fibrosis progression. Pathways involved are multiple, including changes in bile acid metabolism, intestinal ethanol production, generation of short-chain fatty acids, and other by-products. Bile acids act through dedicated bile acid receptors, farnesoid X receptor and TGR5, in both the ileum and the liver, influencing lipid metabolism, inflammation, and fibrogenesis. Currently, both non-alcoholic fatty liver disease and alcohol-related liver disease lack effective therapies, and therapeutic targeting of gut microbiota and bile acids enterohepatic circulation holds promise. In this review, we summarize current knowledge about the role of gut microbiota in the pathogenesis of non-alcoholic fatty liver disease and alcohol-related liver disease, as well as the relevance of microbiota or bile acid-based approaches in the management of those liver diseases.

Використання молочнокислих бактерій як пробіотиків у складі живого корму

The losses in the conditions of intensive aquaculture can be linked with the development of a range of bacterial and viral infectious diseases of hydrobionts. Probiotics are used as the means of treatment and prevention of the dysbiosis of fish organisms. The search for new probiotic cultures and their subsequent trials, the possibility of their co-culturing, using this scientific foundation for devising combined preventative and therapeutic means and their further bioencapsulation in freshwater zooplankton will enable researchers to increase the resistance and responsiveness of fish organisms at the different stages of ontogenesis. The lactic acid bacteria are characterized as being toxic-free and having a wide range of antagonistic activity, namely the development of the colonization resistance of mucous membranes and coats owing to the generation of short-chain fatty acids, bacteriocins, lytic enzymes, antibiotic combinations, the decrease of pH index. This research is dedicated to the elucidation of new probiotic micro-organisms and the possibility of their integration into zooplankton aiming at their further use as the nutritious substrate for fish in the conditions of aquaculture. The thesis presents the results of the conducted analysis of the adhesive properties of probiotic cultures, determines their sensitivity to natural inhibitors as well as the main groups of antibiotics and evaluates the effectiveness of bioencapsulation of bacteria in the organisms of small-sized freshwater crustaceans. The bioencapsulation of mono- or combined probiotics in the organisms of daphnia has increased their survival rates, the length of the bodies of individual representatives of the species and hasn’t had a significant impact upon the correlation of the basic nutrients, which has been established in the course of the description of the biomass chemical content of small-sized crustaceans.

Response of extracellular polymeric substances and enzymatic activity to salinity for the waste activated sludge anaerobic fermentation process.

Salinity (NaCl) was used in waste activated sludge (WAS) anaerobic fermentation system which had been presented to greatly enhance the extracellular polymeric substance (EPS) production including protein and polysaccharide and short-chain fatty acids (SCFAs). Salinity enhanced soluble protein and polysaccharide (SB-EPS) release which was 4.04 times (protein) and 1.83 times (polysaccharide) compared to 0g/L NaCl level. More important, salinity restrained the coenzyme 420 activity (F420), but increased the hydrolase activity. Abundant hydrolysis of substrate and highly active hydrolase led to abundant SCFA production. Pearson correlation coefficient showed that the protein became the main reaction substrate for SCFA generation.

Efficient short-chain fatty acids recovery from anaerobic fermentation of wine vinasse and waste activated sludge and the underlying mechanisms

In this study, the efficient recovery of high-quality short-chain fatty acids from wine vinasse and waste activated sludge mixtures was investigated. The highest accumulation of short-chain fatty acids reached 3502 mg chemical oxygen demand per litre with a proportion of 82.5% acetic and propionic acids in the reactor with a wine vinasse/waste activated sludge mixture under optimized fermentation conditions, while merely 236 and 618 mg chemical oxygen demand per litre was accumulated in the reactors with waste activated sludge and wine vinasse systems alone, respectively. The mechanisms of the exceptional short-chain fatty acids promotion were mainly attributed to the simultaneous increase of bioavailable substrates and the fermentative community. The general microbial activity, key enzymes responsible for short-chain fatty acids generation, and diversity and abundance of fermentative bacteria were all enhanced under optimum conditions, which resulted in the rapid hydrolysis and acidification of bioavailable substrates for short-chain fatty acids generation. Moreover, the dewaterability of fermentation residues was also enhanced due to the presence of wine vinasses as skeleton builders.

How Do Biocides That Occur in Waste Activated Sludge Affect the Resource Recovery for Short-Chain Fatty Acids Production

Anaerobic technology is an efficient and sustainable approach for disposing waste activated sludge (WAS), but the performance is easily affected by environmental conditions. In this study, the potential impacts of chlorhexidine (CHD) and hexadecyltrimethylammonium bromide (HTAB), two highly detected biocides in WAS, on the short-chain fatty acids (SCFAs) generation during anaerobic fermentation were explored. The experimental results indicated that the biocides promoted SCFAs generation unexpectedly, particularly for acetic acid. The accumulation of SCFAs increased from 567.3 mg COD/L in the control to 2144.5 and 3400.0 mg COD/L with low CHD and HTAB exposure (50 mg/L), respectively. However, the enhancing effects were weakened in reactors with high loads of biocides or CHD and HTAB coexistence. Mechanisms exploration revealed that the CHD and HTAB first enhanced the extracellular polymeric substances disruption and then simultaneously accelerated both the hydrolysis and acidification processes while inhi...

Supplementation of Short-Chain Fatty Acid, Sodium Propionate, in Patients on Maintenance Hemodialysis: Beneficial Effects on Inflammatory Parameters and Gut-Derived Uremic Toxins, A Pilot Study (PLAN Study)

Background: In end-stage renal disease (ESRD), gut-derived uremic toxins play a crucial role in the systemic inflammation and oxidative stress promoting the excess morbidity and mortality. The biochemical derangement is in part a consequence of an insufficient generation of short-chain fatty acids (SCFA) due to the dysbiosis of the gut and an insufficient consumption of the fermentable complex carbohydrates. Aim of the study: The primary end-point was to evaluate the potential efficacy of SCFA (specifically, sodium propionate (SP)) for patients on maintenance hemodialysis (MHD) on systemic inflammation. Secondary end-points included potential attenuation of oxidative stress markers, insulin resistance and production of gut-derived uremic toxins indoxyl sulfate and p-cresol sulfate, as well as health status after SP supplementation. Study design: We performed a single-center non-randomized pilot study in 20 MHD patients. They received the food additive SP with a daily intake of 2 × 500 mg in the form of capsules for 12 weeks. Pre-dialysis blood samples were taken at the beginning, after six weeks and at the end of the administration period, as well as four weeks after withdrawal of the treatment. Results: The subjects revealed a significant decline of inflammatory parameters C-reactive protein (−46%), interleukin IL-2 (−27%) and IL-17 (−15%). The inflammatory parameters IL-6 and IFN-gamma showed a mild non-significant reduction and the anti-inflammatory cytokine IL-10 increased significantly (+71%). While the concentration of bacterial endotoxins and TNF-α remained unchanged, the gut-derived uremic toxins, indoxyl sulfate (−30%) and p-cresyl sulfate (−50%), revealed a significant decline. The SP supplementation reduced the parameters of oxidative stress malondialdehyde (−32%) and glutathione peroxidase activity (−28%). The serum insulin levels dropped by 30% and the HOMA-index by 32%. The reduction of inflammatory parameters was associated with a lowering of ferritin and a significant increase in transferrin saturation (TSAT). Four weeks after the end of the treatment phase, all improved parameters deteriorated again. Evaluation of the psycho-physical performance with the short form 36 (SF-36) questionnaire showed an enhancement in the self-reported physical functioning, general health, vitality and mental health. The SP supplementation was well tolerated and without important side effects. No patient had left the study due to intolerance to the medication. The SP supplementation in MHD patients reduced pro-inflammatory parameters and oxidative stress and improved insulin resistance and iron metabolism. Furthermore, SP effectively lowered the important gut-derived uremic toxins indoxyl and p-cresol sulfate. These improvements were associated with a better quality of life. Further controlled studies are required in a larger cohort to evaluate the clinical outcome.

Effect of the prebiotic fiber inulin on cholesterol metabolism in wildtype mice

Dietary non-digestible carbohydrates are perceived to improve health via gut microbiota-dependent generation of products such as short-chain fatty acids (SCFA). In addition, SCFA are also precursors for lipid and cholesterol synthesis potentially resulting in unwanted effects on lipid metabolism. Inulin is a widely used model prebiotic dietary fiber. Inconsistent reports on the effects of inulin on cholesterol homeostasis have emerged in humans and preclinical models. To clarify this issue, the present study aimed to provide an in-depth characterization of the effects of short-chain (sc)- and long-chain (lc)- inulin on cholesterol synthesis, absorption and elimination in mice. Feeding wildtype C57BL/6J mice diets supplemented with 10% (w/w) of either sc- or lc-inulin for two weeks resulted in approximately 2.5-fold higher fecal SCFA levels (P < 0.01) compared with controls, but had no significant effects on plasma and liver lipids. Subtle shifts in fecal and plasma bile acid species were detected with beta-muricholic acid increasing significantly in plasma of the inulin fed groups (1.7-fold, P < 0.05). However, neither sc-inulin nor lc-inulin affected intestinal cholesterol absorption, mass fecal cholesterol excretion or trans-intestinal cholesterol excretion (TICE). Combined, our data demonstrate that sc- and lc-inulin have no adverse effects on cholesterol metabolism in mice despite increased generation of SCFA.

Efficient production of short-chain fatty acids from anaerobic fermentation of liquor wastewater and waste activated sludge by breaking the restrictions of low bioavailable substrates and microbial activity

An efficient approach of bioconverting the organic wastes in liquor wastewater (LW) and waste activated sludge (WAS) to valuable short-chain fatty acids (SCFAs) via anaerobic fermentation was explored. The maximal SCFAs concentration was 5400 mg COD/L with approximate 80.0% acetic and propionic acids under optimized conditions (LW/WAS ratio 1:1, pH 8 and fermentation 4 d). Mechanisms investigation found that the fermentation of LW/WAS made up the drawbacks of sole WAS fermentation by improving the bioavailable substrates and low C/N ratio to stimulate the microbial activities. The bioconversion efficiency of substrates for SCFAs generation was therefore enhanced. The humic acids present in LW could also play positive roles in SCFAs promotion. Moreover, the performance of LW/WAS fermentation was highly correlated with appropriate fermentation pH. The fermentative bacteria responsible for SCFAs production were highly enriched and the activities of key hydrolases, acid-forming enzymes and ATP concentration were greatly improved at pH 8.

Free Ammonia-Based Pretreatment Promotes Short-Chain Fatty Acid Production from Waste Activated Sludge

This work reports a new waste activated sludge (WAS) pretreatment method based on free ammonia (FA) for promoting the generation of short-chain fatty acids (SCFAs). Experimental results showed that pretreatment of WAS for 3 days with FA largely improved WAS disintegration, with the highest dissolution (soluble chemical oxygen demand (COD), 3400 ± 120 mg/L at initial FA level of 237.8 mg/L) being 4.5-fold that without FA pretreatment. The pretreatment method by FA facilitated the breakdown of extracellular polymeric substances and cell envelope of sludge cells and killed more live microbial cells, which thereby accelerated the dissolution of substances from WAS. It was also found that FA severely suppressed the SCFA consumption process, but the acetogenesis process was unaffected. Although FA also inhibited hydrolysis, acidogenesis, and homoacetogenesis to some extent, the inhibitions did not largely affect the biodegradation of the relevant substances at all the tested FA levels. Finally, using FA to pret...

A Review on the Weight-Loss Effects of Oxidized Tea Polyphenols.

The mechanistic systems in the body through which tea causes weight loss are complex and multi-dimensional. Additionally, the bioactive components in tea such as catechins, caffeine, and products of tea polyphenol oxidation vary greatly from one major tea type to the next. Green tea has been the primary subject of consideration for investigation into the preventative health effects of tea because it contains the highest levels of phenolic compounds and retains the highest antioxidant capabilities of any major tea type. However, recent research suggests decreasing body fat accumulation has little to do with antioxidant activity and more to do with enzyme inhibition, and gut microbiota interactions. This paper reviews several different tea polyphenol-induced weight-loss mechanisms, and purposes a way in which these mechanisms may be interrelated. Our original ‘short-chain fatty acid (SCFA) hypothesis’ suggests that the weight-loss efficacy of a given tea is determined by a combination of carbohydrate digestive enzyme inhibition and subsequent reactions of undigested carbohydrates with gut microbiota. These reactions among residual carbohydrates, tea polyphenols, and gut microbiota within the colon produce short-chain fatty acids, which enhance lipid metabolism through AMP-activated protein kinase (AMPK) activation. Some evidence suggests the mechanisms involved in SCFA generation may be triggered more strongly by teas that have undergone fermentation (black, oolong, and dark) than by non-fermented (green) teas. We discussed the mechanistic differences among fermented and non-fermented teas in terms of enzyme inhibition, interactions with gut microbiota, SCFA generation, and lipid metabolism. The inconsistent results and possible causes behind them are also discussed.