Volatile Fatty Acid Production Research Articles

PSI-19 A Saccharomyces Cerevisiae-Derived Postbiotic Stimulates in Vitro Volatile Fatty Acid Production and Influences Hindgut Microbial Population Characteristics

Abstract Horses rely on volatile fatty acids (VFA) to provide a source of energy and fermentative end-products for their health and performance. Improvement in VFA production, has been associated in various species with improved feed conversion and availability of nutrients necessary to maintain epithelial cell growth, blood flow, and the normal secretory and absorptive functions of the intestine and positive changes in the microbial ecology of the gut. In this study, we characterized the effect of a dietary Saccharomyces cerevisiae fermentation postbiotic (SCFP; Diamond V, Cedar Rapids, IA) using an in vitro equine intestinal model to estimate the effects on VFA production and microbiome changes in the horse hindgut. Treatments contained inoculated medium containing a predigested blend of alfalfa and timothy hay substrate and a dilution of fresh equine excreta. The test article (SCFP) was evaluated at 150 mg (TEC) and 225 mg (TECP), in addition to a negative control containing inoculated medium alone, and the positive control containing inulin. The full array of treatments and replicates were incubated anaerobically at 37.2 C for 24 h. VFA concentrations were analyzed by gas chromatography and the microbiome was characterized through shotgun sequencing. Both levels of SCFP supported greater (P < 0.05) acetate, propionate, butyrate, and total VFA production versus the negative control. Greater production of acetate, propionate, butyrate and total VFA was observed for TECP compared with the positive control (P < 0.05). Between the two SCFP treatments, TECP promoted more acetate, propionate and total VFA (P < 0.01), and 18.3% more butyrate than TEC. Significant microbiome changes were also observed, with TEC and TECP promoting greater microbiome diversity (P < 0.05) compared with both negative and positive controls. Compared with the negative control, both levels of SCFP influenced an increased abundance (P < 0.05) of lactic acid producers (Veillonella), butyrate producers (Butyricicoccus, Anaerobutyricum), and an increased abundance of multiple Bacteroides species, all known for their enrichment of carbohydrate-degrading enzymes. Interestingly, our data show a distinct effect of inulin in microbial communities by promoting an increased abundance of Streptococcus species. This study provides evidence that a SCFP can stimulate VFA production, and this effect is incremental with the level of administration which could potentially provide gut health benefits in horses.

284 A Meta-Regression Analysis to Evaluate the Effects of Narasin on Grow-Finish Pig Performance

Abstract Ionophores are a separate class of non-medically important antibiotics used in animal production to increase growth rate. Narasin (Skycis; Elanco Animal Health, Greenfield, IN) is an ionophore labeled for increased rate of body weight gain and improved feed efficiency in growing-finishing swine. The mode of action of this ionophore is to increase energy availability by altering volatile fatty acid production in the hindgut in favor of propionate, which is the most efficient product of fermentation. Therefore, a meta-regression analysis was conducted to evaluate the effects of narasin inclusion in growing-finishing pig diets to predict average daily gain and feed efficiency. A database was developed that contained 21 papers from 2012 to 2021 representing 308 observations including both individual period data as well as overall trial data. For statistical analysis two models were created. The individual period model considered only data with single continuous narasin feeding periods while the overall trial model considered complete data sets representing periods with and without narasin feeding. Regression model equations were developed with the GLIMMIX procedure of SAS (Version 9.4, SAS institute, Cary, NC). Predictor variables were assessed with a step-wise manual forward selection for model inclusion. Predictor variables were required to provide an improvement of at least 2 Bayesian information criterion units to be included in the final model. For individual period data for G:F, the model selected included concentration of narasin in the feed, ADG and ADFI of the control group not provided narasin, and average BW of the control group categorized into greater than 105 kg or less than 105 kg (Table 1). There were 2 competing models to predict improvement in overall G:F. For model 1, significant predictors included concentration of narasin in feed and ADG of the control group. Model 2 for overall G:F included concentration of narasin in feed, ADG and ADFI of the control group. For the individual period model that predicted ADG, the predictors were concentration of narasin in the feed, ADFI, G:F of the control group and BW category for feeding period. The best fitting ADG model using the overall trial data included concentration of narasin in feed, ADFI and G:F of the control group, and feeding duration categorized as longer than 65 days or shorter than 65 days. Together, these models can be used to predict the response to narasin supplementation in finishing pigs. Based on the results, the overall response to narasin inclusion rate for ADG and G:F is quadratic in nature. Additionally, as ADG and G:F increase, the response to narasin supplementation decreases. In summary, using average values from the database for predictor variables, this meta-analysis demonstrates narasin would be expected to improve overall G:F from 0.74 to 1.13% and ADG from 1 to 3%.

Disinfectant sodium dichloroisocyanurate synergistically strengthened sludge acidogenic process and pathogens inactivation: Targeted upregulation of functional microorganisms and metabolic traits via self-adaptation

Harmless and resourceful treatment of waste activated sludge (WAS) have been the crucial goal for building environmental-friendly and sustainable society, while the synergistic realization approach is currently limited. This work skillfully utilized the disinfectant sodium dichloroisocyanurate (NaDCC) to simultaneously achieve the pathogenic potential inactivation (decreased by 60.1 %) and efficient volatile fatty acids (VFAs) recovery (increased by 221.9 %) during WAS anaerobic fermentation in rather cost-effective way (Chemicals costs:0.4 USD/kg VFAs versus products benefits: 2.68 USD/kg chemical). Mechanistic analysis revealed that the C=O and NCl bonds in NaDCC could spontaneously absorb sludge (binding energy -4.9 kJ/mol), and then caused the sludge disintegration and organic substrates release for microbial utilization due to the oxidizability of NaDCC. The disruption of sludge structure along with the increase of bioavailable fermentation substrates contributed to the selectively regulation of microbial community via enriching VFAs-forming microorganisms (e.g., Pseudomonas and Streptomyces) and reducing VFAs-consuming microorganisms, especially aceticlastic methanogens (e.g., Methanothrix and Methanospirillum). Correspondingly, the metabolic functions of membrane transport, substrate metabolism, pyruvate metabolism, and fatty acid biosynthesis locating in the central pathway of VFAs production were all upregulated while the methanogenic step was inhibited (especially acetate-type methanogenic pathway). Further exploration unveiled that for those enriched functional anaerobes were capable to activate the self-adaptive systems of DNA replication, SOS response, oxidative stress defense, efflux pump, and energy metabolism to counteract the unfavorable NaDCC stress and maintain high microbial activities for efficient VFAs yields. This study would provide a novel strategy for synergistic realization of harmless and resourceful treatment of WAS, and identify the interrelations between microbial metabolic regulations and adaptive responses.

Simultaneous nitrogen and phosphorus control from alkali and zeolite sludge fermentation process: Mechanism and application

Sludge alkali fermentation (NaOH treatment) can achieve a substantial production of volatile fatty acids (VFAs) while releasing a large amount of ammonia nitrogen (NH4+-N) and phosphorus (PO43--P). To address these issues, a combination of zeolite and NaOH/Ca(OH)2 mixed alkali fermentation was proposed. The results demonstrated that the concentration of PO43--P with mixed alkali treatment was 17.9 mg/L, whereas it was 109.21 mg/L for the NaOH treatment group. At the 8th day, the VFAs production was 1.42 times higher than the control group when using NaOH/Ca(OH)2 mixed alkali treatment. Furthermore, the addition of zeolite strengthened the fermentation by adsorbing NH4+-N. Besides, the sludge after fermentation had good dehydration performance and increased microbial community diversity and richness. Macellibacteroides, Proteiniclasticum, Exiguobacterium, Sporacetigenium and Bacillus were the dominant microorganisms with zeolite treatment. Zeolite combined with mixed alkali induced metabolic changes and the abundances of amino acid and carbohydrate metabolisms were the highest.

Cascading Integration of Electrofermentation and Photosynthesis—Low‐Carbon Biorefinery in Closed Loop Approach

AbstractSingle‐chambered electrofermentation (EF) bioreactors are operated using spent wash to evaluate the effect of applied voltage (EF/AV; −0.6 V) against closed‐circuit (EF/CC; 100 Ω) and control (EF/C; no voltage/resistance) operations using deoiled microalgae biomass‐derived biochar electrodes (anode) on increasing acidogenesis rate/efficiency. Higher total volatile fatty acids (VFA) production (mg L−1) is observed in EF/AV (2866), depicting 31% and 57% increments than EF/CC (1984) and EF/C (1224), respectively. The VFA profiles (C2–C4) in EF/AV are higher with acetic/butyric/propionic acids (1922/704/240 mg L−1) and biogas co‐generation [H2 (22%) and CH4 (3%)] than EF/CC and EF/C. The applied voltage (EF/AV) helps in electron flux regulation for increasing substrates conversion and VFA generation. Residual VFA‐rich effluents from EF process is utilized as substrate to mixotrophic microalgae cultivation (nutrient‐ and stress‐phase) that resulted in biomass production with simultaneous wastewater treatment. EF/AV depicts higher biomass growth (0.72 g L−1; 4th day) and substrate removal (63%) than other operations. Integrations of electrofermentation with photosynthetic processes operated with the residual resources in effluents towards product valorization and wastewater polishing, accounts for low‐carbon economy.

The Dose-Dependent Role of Sage, Clove, and Pine Essential Oils in Modulating Ruminal Fermentation and Biohydrogenation of Polyunsaturated Fatty Acids: A Promising Strategy to Reduce Methane Emissions and Enhance the Nutritional Profile of Ruminant Products

The livestock industry significantly contributes to greenhouse gas emissions, with ruminant animals, including cows, sheep, and goats, being responsible for a substantial share of these emissions due to methane production. Reducing methane emissions from ruminants is crucial for mitigating the environmental impact of livestock production. Additionally, there has been a growing interest in improving the nutritional quality of ruminant products through modifying their profile of fatty acids. The current study aimed to investigate the potential of sage (SAG), pine (PIN), and clove (CLO) essential oils as natural additives for modulating in vitro ruminal fermentation characteristics and biohydrogenation of polyunsaturated fatty acids (PUFA). Within the current experiment, three dose levels (300, 600, and 900 mg/L) of essential oils were evaluated using rumen inoculum from three mature Dalagh ewes (58 ± 2.84 kg body weight). The results revealed that the essential oils had a significant impact on gas production, methane and carbon dioxide production, ruminal fermentation parameters, and ruminal biohydrogenation of dietary PUFAs. The essential oil treatments resulted in reduced gas production compared with the control group. Methane production was significantly reduced by all doses of the essential oils, with the highest dose of CLO resulting in the lowest methane production. In addition, the essential oils affected ruminal fermentation parameters, including pH, ammonia concentration, and production of total volatile fatty acids. Promising modifications in ruminal biohydrogenation of PUFAs and the profile of fatty acids were also observed in the current study. These findings suggest that SAG, Pin, and CLO hold promise in mitigating methane emissions and improve the nutritional value of ruminant products. Further investigation is required to evaluate their effectiveness in practical feeding strategies for livestock.

Effects of wheat bran replacement with pomegranate seed pulp on rumen fermentation, gas production, methanogen and protozoa populations of camel and goat rumen using competitive PCR technique: An in vitro study.

Microbial populations in the rumen play an essential role in the degradation of Cellulosic dietary components and in providing nutrients to the host animal. This study aims to detect the effect of pomegranate seed pulp (PSP) on rumen fermentation, digestibility and methanogens and the protozoa population (by competitive polymerase chain reaction [PCR]) of the camel and goat rumen fluid. PSP was added to the experimental treatments and replaced by wheat bran (0%, 5% and 10%). Rumen fluid was collected from three goats and two camels according to the similarity of sex, breed, origin and time and used for three gas production studies. DNA extraction was performed by the RBB+c method, the ImageJ programme calculated band intensities (target and competing DNA), and line gradients were plotted based on the number of copies and intensity. Our result showed that diets did not significantly affect the methanogen and protozoa population. Animal species affected microbial populations so that both populations in camels were less than goats. The production of gas and volatile fatty acids was not affected by diets. These two parameters and NH3 concentration and methane production in goats were higher than in camel. The pH of digested dry matter and microbial protein in camels was higher than in goats. Therefore, the competitive PCR technique is an effective method for enumerating rumen microbiota. This supplementation can be considered a strategy to achieve performance and environmental benefits.

The Chemical Characteristics and In Vitro Degradability of Pineapple By-Products as Potential Feed for Ruminants.

Pineapple fruit, which is cultivated in tropical and subtropical areas, is processed by the food industry, generating a large amount of waste. Using pineapple by-products in animal nutrition could reduce feeding costs and contribute to the containment of pollution. The chemical composition and the in vitro fermentation of five pineapple by-products (crown, bud end, peel, core, and pomace) from two West African pineapple varieties (Smooth Cayenne-SC and Sugarloaf-SL) were evaluated. Significant differences were observed between the varieties and by-products. The dry matter (DM) content was low and superimposable between varieties, averaging 17.7%. On a DM basis, pomace showed the highest protein content (SC 8.10% and SL 8.81%, p < 0.001), whereas the crown showed the highest (p < 0.001) NDF content (47.62% and 39.01% for SC and SL, respectively). Due the high sugar content, the core and pomace showed high in vitro organic matter degradability (SC: 85.09% and SL: 83.98%), estimated metabolizable energy (SC: 7.91 KJ/kg and SL: 7.66 KJ/kg), and volatile fatty acid production (96.86 mmol/g and 90.62 mmol/g). Based on chemical composition and in vitro digestibility results, this study suggests that pineapple by-products have the potential to be used in ruminants' diets, considering the crown, bud end, and peel as fiber sources and the core and pomace as substitutes or supplements to concentrate feedstuffs. Further research should be conducted on the storability of these by-products through in vivo trials evaluating animals' performances and the quality of their products.

Impact on the microbial population during biological volatile fatty acid production from olive mill solid waste

Volatile fatty acids (VFAs) revalorisation from waste products are key in achieving industrial sustainability and circular economic goals. Hence, the objective of this work was to correlate the adaptability of the microbial community in olive mill solid waste (OMSW) anaerobic fermentation processes, to the production of VFAs under different pH conditions, i.e. under acidic (pH 4 &5), neutral (pH 6 & 7) and alkaline conditions (pH 9 & 10). At neutral conditions, anaerobic digestion exhibited minimal accumulation of VFAs, as they were primarily biotransformed to methane, where no significant changes in the microbial community were observed. At acidic conditions, a diverse profile of VFAs were present in the reactors, although the VFA production was limited to around 20 % of fed OMSW. Despite the low accumulation, the VFA profile at pH 5 was more complex than those at alkaline conditions, accounting propionic acid as the main VFA compound produced at pH 5 (60 % of the total VFAs). Acidic conditions entailed a shift in the microbial composition compared to the initial inoculum, although the reactors maintained similar diversity indices. At alkaline conditions, around 50 % of the fed OMSW was accumulated as VFAs, mainly as acetic acid. Overall, a lower diversity and higher dominance corresponded to a less diverse VFAs profile, such as the preponderance of acetic acid correlated with a microbial diversity decrease and the increased dominance of Tissirella.

Marine Macroalgae in Rabbit Nutrition: In Vitro Digestibility, Caecal Fermentability, and Microbial Inhibitory Activity of Seven Macroalgae Species from Galicia (NW Spain)

The limitation on the prophylactic use of antibiotics in animal feed in Europe has critically challenged the rabbit meat industry, which urgently needs to find solutions. A feasible alternative could be using macroalgae in the diet to improve the gut health. This research studied seven species of marine macroalgae in four formats (dehydrated, enzymatically hydrolyzed, aqueous extract, and aqueous extract of hydrolyzed macroalgae) in order to select the most promising ones for their use in rabbit feed. Chemical composition, in vitro digestibility, in vitro caecal gas, total volatile fatty acid (VFA) production, and minimal inhibitory concentrations (MIC) against common pathogens were studied. All S. latissima products showed high caecal fermentability and VFA production, especially in both types of extracts. The H. elongata aqueous extract was remarkable due to its high in vitro butyrate production, which can be of great interest for improving gut health. The MIC results did not indicate any clear inhibition of the pathogens tested. The macroalgae tested appear to have a potentially prebiotic effect, rather than a direct antimicrobial activity. However, these results must be confirmed in vivo, in order to observe the real benefits of feeding macroalgae during the rabbit weaning period.

Sourdough process and spirulina-enrichment can mitigate the limitations of colon fermentation performances of gluten-free breads in non-celiac gut model

In this work, the impact of gluten free (GF) breads enriched with spirulina on the ecology of the colon microbiota of non-celiac volunteers was investigated. Simulation of digestion of GF breads was conducted with an in vitro gut model. Microbiomics and metabolomics analyses were done during colon fermentations to study the modulation of the microbiota.From the results, a general increase in Proteobacteria and no reduction of detrimental microbial metabolites were observed in any conditions. Notwithstanding, algae enriched sourdough breads showed potential functionalities, as the improvement of some health-related ecological indicators, like i) microbiota eubiosis; ii) production of bioactive volatile organic fatty acids; iii) production of bioactives terpenes. Our results indicate that a sourdough fermentation and algae enrichment can mitigate the negative effect of GF breads on gut microbiota of non-celiac consumers.

Self-fermented agro-wastes as antioxidant enriched maize grain replacer for sustainable animal feeding

Piles of agro-wastes resulting from quantum agro-industrial growth can be best utilized as animal feed, reducing envionmental impact by 50–95% depending on their nutritive value. However, palatability issues have limited their use, which can be addressed by combining them based on their nutritional value. Thus present three-phase study aimed to utilize these waste materials as animal feed by utilizing a self-fermentation approach. Six combinations of apple pomace (AP), spent mushroom compost (SMC) and wheat straw were self-fermented and analysed for quality in phase-I. Phase-II assessed the best combination obtained from phase-I as an antioxidant-enriched maize replacer (AEMR) by replacing maize (0–32%) in total mixed ration (TMR) under in-vitro ruminal conditions and two best TMR were assessed for nutrient utilization under metabolic trial. In phase-III, the three-month feeding effect of AEMR on the overall growth performance of male Gaddi goat kids was assessed. Findings showed that 85:7.5:7.5 proportion had optimal pH (3.92), significantly higher lactic acid (5.29 g 100−1 g DM), water soluble carbohydrates (2.29 g 100−1 g DM) and oxidative and microbial stability (Lactobacillus: 8.38 log10 cfu g−1). Fermentation also resulted in significant increase in antioxidant activities. AEMR exhibited a significant reduction in CH4 and NH3–N and higher volatile fatty acid production under in-vitro conditions at 32% level with no adverse effects on nutrient utilization. AEMR feeding also exhibited significantly improved feed conversion ratio (FCR) and serum lipid and oxidative profiles. In conclusion, AP and SMC in combined form can be utilized as an AEMR through self-fermentation at 32% level in TMR which may serve as a promising and sustainable approach for reducing environmental footprints and boosting eco-friendly livestock production.

Enhancing scalability and economic viability of lignocellulose-derived biofuels production through integrated pretreatment and methanogenesis arrest

The pursuit of affordable biofuels necessitates continuous refinement of valorization strategies, focusing on cost-effective feedstocks, accessible bioprocessing, and high-quality products. High energy input required during various stages, including pretreatment, post-pretreatment, and methanogenesis arrest, impeded the economic lignocellulose-derived biofuels production from anaerobic digestion (AD). Addressing this challenge, an upstream process integrating synergistic alkali pretreatment and arrested AD was proposed. Results demonstrated that an optimum reactor pH 10 yielded a volatile fatty acids (VFA) titer of 3.6 gCOD/L, only 23% lower than using methanogenesis inhibitor. The study further explored the interplay between initial pH, cell viability/functionality, and VFA production by assessing cell viability and cell population demographics. This integrated approach demonstrated a VFA yield of 364 gVFA/kgTSsubstrate at a cost of just USD 0.2/kgVFA, encompassing post-pretreatment and methanogenesis arrest, which underscores the viability of combining pretreatment and methanogenesis arrest for cost effective and scalable biofuels production.

The Catalytic Wet Oxidation of Excess Activated Sludge from a Coal Chemical Wastewater Treatment Process

An improved catalytic wet oxidation method for the disposal of excess activated sludge from a coal chemical wastewater treatment process by using the prepared Cu-Ce/γ-Al2O3 catalyst was reported. The effects of catalyst dosage, reaction temperature and time, and initial oxygen pressure on the degradation of the sludge were investigated. The maximum removal rate of volatile suspended solids, 93.2%, was achieved at 260 °C for 60 min with the catalyst 7.0 g·L−1 and initial oxygen pressure 1.0 MPa. The removal rate of chemical oxygen demand was 78.3% under the same conditions. The production of volatile fatty acids, including mainly acetic acid, propanoic acid, and isobutyric acid, increased with the increasing temperature. These acids have the potential to be carbon sources for the biological treatment of wastewater. Scanning electron microscopy images showed that the sludge became a loose porous structure, which is beneficial for dewatering performance. The results of an energy dispersive spectroscopy analysis illustrated that the carbon element in the sludge substantially migrated from solid to liquid phases. Therefore, these results demonstrated that the proposed catalytic wet oxidation method offers a promising pathway for the disposal and utilization of excess activated sludge from the coal chemical wastewater treatment process.

Dual oxidant strategy involving calcium peroxide and peroxydisulfate for waste activated sludge recycling: Removal of sulfamethoxazole and hydrocortisone

In this study, the removal of sulfamethoxazole (SMX) and hydrocortisone (HC) from waste activated sludge (WAS) was explored using a dual oxidant strategy involving calcium peroxide (CaO2) and peroxydisulfate (PDS). Synergistic effects were observed between CaO2 and PDS at 0.1 g/g TS (total solids), leading to 89 % and 54 % removal of SMX and HC, respectively, in 8 min in sludge. Ca2+, Ca(OH)2, H2O2, and SO42– from CaO2 and PDS hydrolysis promoted pollutant removal. SMX removal was mainly driven by 1O2, which had a 78 % contribution to the removal rate, while HC removal was mainly due to OH and SO4–, with an overall 79 % contribution. Furthermore, removal pathways for SMX and HC during CaO2/PDS were proposed. SMX, HC, and their intermediates with high toxicity transformed into less toxic or nontoxic products during CaO2/PDS oxidation. Moreover, the dewatering ability and solubility of sludge increased after CaO2/PDS treatment. Furthermore, the production of volatile fatty acids during anaerobic fermentation of sludge pretreated with CaO2/PDS increased by 1.8 times relative to the control, with a 13 % increase in acetic acid content. The altered relative abundance of Firmicutes and Proteobacteria played a key role in promoting the recovery of carbon sources from the sludge.

Optimization of Long-Chain Fatty Acid Synthesis from CO 2 Using Response Surface Methodology

A microbial electrosynthesis cell (MES) is an electrochemical technique in which electrolithoautotrophic electroactive microbes fix carbon dioxide (CO2) to longer-chain volatile fatty acids (VFAs). The synthesis of VFAs from CO2 requires optimization to improve the MES performance for industrial feasibility. This work studied the effect of different parameters, such as pH, headspace gas pressure, ethanol concentration, electrolyte, and trace element concentrations, on VFA synthesis from CO2 that used mixed anaerobic consortia in serum bottles. The operational parameters were varied according to a central composite design (CCD) and response surface methodology (RSM). A global optimum for the response variables was determined. The optimum values of different operating factors to maximize VFA production that was obtained from the optimizations were 1.12 × 105 Pa pressure, pH 7.149, ethanol = 2,318.7 mg/L, three times the standard Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ) 300 electrolyte concentration and five times the standard DSMZ 300 trace elements concentration. The experimental study was validated in triplicate, which considered the optimal values. The rate of total VFA production that was obtained from the operational parameters experimental study was 43.7 ± 5.9 mg/L/day under this optimized condition, which agreed with the predicted value of 30.39 mg/L/day. For the media optimization, validation of the experimental study was conducted at the optimal values, and their experimental response was 79.75 ± 19.26 mg/L/day, and the predicted response was 75.89 mg/L/day for total VFA production rates.

Deeper Insights into the Effect of Humic Acid on Kitchen Waste Anaerobic Digestion: Enzyme Activities, Microbial Community Dynamics, and Key Metabolic Pathways

Anaerobic digestion (AD) represents one of the most eco-friendly approaches for recovering the energy from kitchen waste (KW). This study investigated the impact of humic acid (HA) on AD of KW. Batch experiments were conducted using KW as the substrate, with varying HA dosages. The results revealed that an increase in HA dosage led to an inhibition of methanogenic efficiency by 29.51% and a delayed start-up of AD. The HA exhibited dual effects on enzyme activities during AD, inhibiting hydrolytic enzymes while stimulating acidogenic enzymes. This unique interaction ultimately resulted in a significant 12.32% increase in volatile fatty acid production. Furthermore, HA induced the generation of reactive oxygen species and had a discernible impact on the activity of the electron transfer system. A bioinformatics analysis highlighted that HA promoted the abundance of microorganisms with mediated interspecies electron transfer ability, including DMER64 and Methanosaeta, as well as the Firmicutes phylum, while significantly reducing the abundance of Methanobacterium. Moreover, the KEGG pathway analysis revealed a decrease in hydrolysis and methanogenesis-related genes and an increase in acidogenesis-related genes.

Methane reduction by quercetin, tannic and salicylic acids: influence of molecular structures on methane formation and fermentation in vitro

Plant secondary metabolites (PSMs) can potentially reduce ruminal methane formation. However, related to differences in their molecular structures, it is not yet clear what causes an anti-methanogenic effect. In an in vitro system simulating rumen fermentation, we investigated the impact of eight compounds with distinct chemical characteristics (gallic and salicylic acids, tannic acid, catechin, epicatechin, quercetin, rutin, and salicin) when added to a basal feed (maize silage) at a concentration of 12% of the feed dry matter. After 48 h of incubation in buffered rumen fluid, methane production was significantly lowered by quercetin (43%), tannic acid (39%) and salicylic acid (34%) compared to the control (maize silage alone) and without changes in total volatile fatty acid production during fermentation. No other PSM reduced methane formation as compared to control but induced significant differences on total volatile fatty acid production. The observed differences were related to lipophilicity, the presence of double bond and carbonyl group, sugar moieties, and polymerization of the compounds. Our results indicate the importance of distinct molecular structures of PSMs and chemical characteristics for methane lowering properties and volatile fatty acid formation. Further systematic screening studies to establish the structure–function relationship between PSMs and methane reduction are warranted.

Recovery of an acidified food waste anaerobic digestion reactor via NH4+-N and trace metals addition: Performance, microbial community response, and mechanisms

An increased organic loading rate can lead to an imbalance in the production and consumption of volatile fatty acids (VFAs) during anaerobic digestion of food waste, ultimately resulting in reactor acidification. In this study, VFA consumption was enhanced by adding NH4+-N and trace metals (TMs) (Fe, Co, Mo, and Ni). The addition of NH4+-N (330 mg/L) decreased the VFAs concentration in the reactor from 1477.54 to 223.83 mg/L, and remained below 400 mg/L during subsequent operation. The addition of NH4+-N enhanced the acid-base buffering capacity of the reactor, thereby detaching methanogens from the acidified environment and restoring their activity. The addition of TMs gradually decreased the VFAs concentration in the reactor from 3926.23 to 230–330 mg/L. TMs directly enhanced the methanogenic activity and enriched functional methanogens (Methanosarcina) with high acetic acid utilisation efficiency, thereby alleviating reactor acidification.

Assessment of the Impact of Coffee Waste as an Alternative Feed Supplementation on Rumen Fermentation and Methane Emissions in an In Vitro Study

Spent coffee waste is the most common by-product of coffee processing, and it has the potential to be used as a source of organic compounds for ruminant diets. The objective of this study was to evaluate the optimal inclusion level and method for using spent coffee waste (SCW) as a ruminant feed and investigate its effects on rumen fermentation characteristics and methane (CH4) production. The present in vitro batch culture study was conducted using two different experimental designs. The first experimental design (TRIAL. 1) was performed using a control diet of 500 mg of fresh matter basal diet (60% hay/40% concentrate), with SCW being used as a feed additive at 1%, 10% and 20% of the substrate. The second experimental design was performed using the same control diet, with spent coffee waste replacing either part of the hay (TRIAL. 2) or some of the concentrate mixture (TRIAL. 3) at four different dosages (30:70, 50:50, 70:30 and 100). When SCW was supplemented as a feed additive, there were increases in the production of volatile fatty acids and gas; however, it did not show any suppressive effects on CH4 production. In contrast, when SCW was included as a replacement for hay or concentrate, there were significant reductions in CH4 production with increasing levels of SCW inclusion. These reductions in CH4 production were accompanied by negative effects on nutrient digestibility and total volatile fatty acid production. These findings demonstrate that SCW could potentially be used as a prebiotic feed additive. Additionally, when SCW is used as a replacement for silage at 70:30 and 50:50 dosages appear to be feasible as a substitute for animal feed (hay and concentrate).