Major Volatile Fatty Acids Research Articles

Effects of feeding sulfate trace minerals above recommendations on nutrient digestibility, rumen fermentation, lactational performance, and trace mineral excretion in dairy cows

Most trace minerals (TM) are fed above dairy cow requirements in commercial herds but their fate and effects on dairy cows have not been well documented. In this study, we evaluated the effects of feeding short-term sulfate TM above recommendations on apparent total-tract digestibility of nutrients, rumen fermentation characteristics, serum concentrations, milk yield and composition as well as milk, fecal, and urinary TM excretion in mid-lactation dairy cows. Eight multiparous Holstein cows [average body weight: 684 (SD: 29) kg at 82 (SD: 10) days in milk] in a quadruple 2 × 2 crossover design were fed a basal diet, differing in sulfate TM supplement concentrations, to provide either 0.11, 17, and 63 (control; CON) or 0.95, 114, and 123 (high trace minerals; HTM) mg of dietary Co, Mn, and Zn/kg of dry matter, respectively. Each experimental period had a 21-d adaptation to the diet, followed by a 10-d sample collection period. Feed ingredients and total feces and urine were collected during 4 consecutive d and rumen fluid was collected 0, 1, 2, 4, and 6 h relative to feeding. Milk yield was recorded daily and milk samples were collected on 4 consecutive milkings. Ingestion of Co, Mn, and Zn was higher for HTM compared with CON group by 216, 233, and 93%, respectively. Dry matter intake averaged 25.0 (SE = 0.6) kg/d, and apparent total-tract digestibility of major nutrients was similar between treatments. There was no measurable effect of HTM on ruminal pH, major volatile fatty acids, and protozoa counts. Isovalerate molar proportion was 9.4% greater for HTM compared with CON group. Neither milk yield (43.5 kg/d; SE = 0.8) nor milk fat and protein concentrations differed between treatments. Milk urea nitrogen concentration was significantly higher for HTM (11.7 mg/dL) compared with CON group (9.7 mg/dL; SE = 0.7). Fecal excretion of Co, Mn, and Zn increased by 223, 198, and 75%, respectively, for HTM compared with CON group. Urinary excretions of TM were marginal compared with feces, and only urinary Co and Mn were significantly higher for HTM than CON cows as similarly obtained for serum Co and Mn concentrations. Milk TM yields were not modified by treatments. In summary, short-term dietary sulfate TM supply over the recommendation did not improve cow performance but significantly increased fecal TM excretion, which could have impacts on TM accumulation in soils where manure is applied and could potentially result in leaching into nearby watersheds. Further studies are needed to evaluate the impact of high fecal TM excretion on the environment using the One Health approach. Moreover, the impacts of TM oversupply on milk production and cow health should be evaluated by long-term experiments.

Chemical and biological effects of zero-valent iron (ZVI) concentration on in-situ production of H2 from ZVI and bioconversion of CO2 into CH4 under anaerobic conditions

The conversion of carbon dioxide (CO2) to methane (CH4) is a strategy for sequestering CO2. Zero-valent iron (ZVI) has been proposed as an alternative electron donor for the CO2 reduction to CH4. In this study, the effects of ZVI concentrations on the abiotic production of H2 (without the action of microorganisms) in the first part and on the biological conversion of CO2 to CH4 using ZVI as a direct electron donor in the second part were examined. In the abiotic H2 production, the increase in the ZVI concentration from 16 to 32, 64, and 96 g/L was found to have positive effects on both the amounts of H2 generated and the rates of H2 production because the extent of ZVI oxidation positively correlates with increasing surface area. Nevertheless, the increase in ZVI concentration from 96 to 224 g/L did not benefit the H2 production because the ZVI dissolution was suppressed by the increasing aqueous pH above 10. In the bioconversion of CO2 to CH4 using ZVI as an electron donor, the main methanogenesis pathway occurred via hydrogenotrophic methanogenesis at pH 8.7–9.5 driven by the genus Methanobacterium of the class Methanobacteria. At ZVI concentrations of 64 g/L and above, the production of volatile fatty acid (VFA) became clear. Acetate was the main VFA, indicating the induction of homoacetogenesis at ZVI concentrations of 64 g/L and above. In addition, the presence of propionate as the second major VFA suggests the production of propionate from CO2 and acetate under conditions with high H2 partial pressure. The results indicated that the pathway for ZVI/CO2 conversion to CH4 was competitive between hydrogenotrophic methanogenesis and homoacetogenesis.

Rumen fermentation of meal-fed sheep in response to diets formulated to vary in fiber and protein degradability.

The concentration of volatile fatty acid (VFA) provides an imprecise view of VFA dynamics due to the confounding effects of fluid pool size and dynamics. Determination of VFA flux using isotope is expensive and a complex methodology. Therefore, a rapid and affordable approach to explore VFA dynamics may allow comprehensive characterization of VFA availability. The objective of this study was to explore the use of VFA dynamics generated by meal feeding to derive time-series rates of VFA apparent appearance and disappearance driven by different protein and fiber sources. Six ruminally cannulated wethers were fed diets containing timothy hay or beet pulp (TH and BP) and soybean meal (SBM) or heated soybean meal (HSBM). Diets were, TH + HSBM; TH + SBM; BP + HSBM; and BP + SBM and the experimental design was a partially replicated 4 × 4 Latin Square. Concentrations of VFA and polyethylene glycol (PEG) in rumen fluid samples were estimated. Concentrations of PEG were used to estimate fluid passage and volume to calculate VFA mass, and fluid-mediated exit. Maximum apparent appearance rate (mmol/h), the rate of apparent appearance decline (mmol/mmol/h), mean apparent appearance flux (mmol/h), mean apparent disappearance (mmol/h), and apparent disappearance rate (mmol/mmol/h) were estimated by deriving a 1 pool model for each VFA on a mass basis where appearance was assumed to follow an exponential decay pattern and disappearance followed mass-action kinetics. Statistical analyses were conducted using a linear mixed effect regression with fixed effects for fiber source, protein source, and their interaction, as well as random effects for animal and period. Rumen fluid volume (L) was greater in HSBM diets (P = 0.033) and fluid passage (%/h) was greater in SBM diets (P = 0.048). Concentrations (higher acetate and butyrate, P = 0.002 and 0.004, respectively) and molar proportions (higher valerate, P = 0.035) of VFA were affected only by fiber source; however, protein source and fiber source interacted to significantly influence apparent appearance rates and absorption rates of many major VFA. On a flux basis, HSBM supported significantly elevated mean disappearance of propionate (P = 0.033). This data demonstrates that time-series evaluation of fermentation dynamics, including fluid dynamics and VFA concentrations can be used to estimate apparent appearance and disappearance of VFA. Although further work is needed to confirm the alignment of these estimates with measurements of VFA supplies to the animal, this modeling approach may provide a simpler way to better understand the kinetics of rumen.

Effects of acetate, propionate, and pH on volatile fatty acid thermodynamics in continuous cultures of ruminal contents.

To investigate the effects of acetate, propionate, and pH on thermodynamics of volatile fatty acids (VFA) in the rumen, a dual-flow continuous culture study was conducted to quantify production of major VFA, interconversions among the VFA, and H2 and CH4 emissions in a 4 × 4 Latin square design. The 4 treatments were (1) control: pH buffered to an average of 6.75; (2) control plus 20 mmol/d of infused acetate (InfAc); (3) control plus 7 mmol/d of infused propionate (InfPr); and (4) a 0.5-unit decline in pH elicited by adjustment of the buffer (LowpH). All fermentors were fed 40 g of a pelleted diet containing whole alfalfa pellets and concentrate mix pellets (50:50) once daily. After 7 d of treatment, sequential, continuous infusions of [2-13C] sodium acetate (3.5 mmol/d), [U-13C] sodium propionate (2.9 mmol/d), and [1-13C] sodium butyrate (0.22 mmol/d) were carried out from 12 h before feeding for 36 h. Filtered liquid effluent (4 mL) was sampled at 0, 2, 4, 6, 8, 12, 16, and 22 h after feeding, and assessed for VFA concentrations, with another filtered sample (20 mL) used to quantify aqueous concentrations of CH4 and H2. Headspace CH4 and H2 gases were monitored continuously. Ruminal microbes were isolated from the mixed effluent samples, and the microbial community structure was analyzed using the 16S rRNA amplicon sequencing technique. The digestibility of neutral detergent fiber, acid detergent fiber, and starch and microbial C sequestrated from VFA were not affected by treatments. The LowpH treatment increased net propionate production and decreased H2 and CH4 headspace emissions, primarily due to shifts in metabolic pathways of VFA formation, likely due to the observed changes in bacterial community structure. Significant interconversions occurred between acetate and butyrate, whereas interconversions of other VFA with propionate were relatively small. The InfAc and InfPr treatments increased net acetate and propionate production, respectively; however, interconversions among VFA were not affected by pH, acetate, or propionate treatments, suggesting that thermodynamics might not be a primary influencer of metabolic pathways used for VFA formation.

Microbial Communities of Artisanal Fermented Milk Products from Russia.

Fermented milk products (FMPs) have numerous health properties, making them an important part of our nutrient budget. Based on traditions, history and geography, there are different preferences and recipes for FMP preparation in distinct regions of the world and Russia in particular. A number of dairy products, both widely occurring and region-specific, were sampled in the households and local markets of the Caucasus republics, Buryatia, Altai, and the Far East and European regions of Russia. The examined FMPs were produced from cow, camel, mare's or mixed milk, in the traditional way, without adding commercial starter cultures. Lactate and acetate were the major volatile fatty acids (VFA) of the studied FMPs, while succinate, formate, propionate and n-butyrate were present in lower concentrations. Bacterial communities analyzed by 16S rRNA gene V4 fragment amplicon sequencing showed that Firmicutes (Lactococcus, Lactobacillus, Streptococcus, Lentilactobacillus and Leuconostoc) was the predominant phylum in all analyzed FMPs, followed by Proteobacteria (Acetobacter, Klebsiella, Pseudomonas and Citrobacter). Lactobacillus (mainly in beverages) or Lactococcus (mainly in creamy and solid products) were the most abundant community-forming genera in FMPs where raw milk was used and fermentation took place at (or below) room temperature. In turn, representatives of Streptococcus genus dominated the FMPs made from melted or pasteurized milk and fermented at elevated temperatures (such as ryazhenka, cottage cheese and matsoni-like products). It was revealed that the microbial diversity of koumiss, shubat, ryazhenka, matsoni-like products, chegen, sour cream and bryndza varied slightly within each type and correlated well with the same products from other regions and countries. On the other hand, the microbiomes of kefir, prostokvasha, ayran, cottage cheese and suluguni-like cheese were more variable and were shaped by the influence of particular factors linked with regional differences and traditions expressed in specificities in the production process. The microbial diversity of aarts, khurunga, khuruud, tan, ayran and suluguni-like cheese was studied here, to our knowledge, for the first time. The results of this study emphasize the overall similarity of the microbial communities of various FMPs on the one hand, and specificities of regional products on the other. The latter are of particular value in the age of globalization when people have begun searching for new and unusual products and properties. Speaking more specifically, these novel products, with their characteristic communities, might be used for the development of novel microbial associations (i.e., starters) to produce novel products with improved or unique properties.

369 Effect of Diet, Rumen Fermentation Parameters and Their Combination on Predicting Milk Production

Abstract The objective of this meta-analysis was to explore variability in milk production associated with rumen fermentation parameters and diet characteristics. Data were extracted from 138 journal articles and used to derive 6 models to predict MY. Each model considered a different set of independent variables, including rumen fermentation parameters (R), diet (D) and their combination (R+D), with or without interactions with rumen pH. Rumen fermentation parameters included total volatile fatty acid (VFA) concentration, molar proportions of major and minor VFA, rumen pH and ammonia nitrogen, and diet variables included dry matter intake (DMI) dietary percentages of dry (DM) and organic matter (OM), crude protein, neutral (NDF) and acid detergent fiber (ADF), ether extract, and starch. Linear mixed-effects models weighted by the inverse of the standard error were employed. Models were compared based on concordance correlation coefficients after removing random study effects (CCC). The MY models using D, R, D+R and D*pH performed similarly with CCC values ranging from 0.63 to 0.65. Models including an interaction with rumen pH were superior at explaining variation within the data (CCC: 0.75 to 0.76). The Final model derived using D, consisted of DMI and ADF. Molar proportions of acetate and propionate and DMI were in the final model based on R. The interaction between starch and pH remained in the final D*pH model along with DMI, DM, NDF and pH. From these models, we can conclude that rumen pH is an important moderator explaining variability in the associations among diet, rumen VFA, and milk production.

PSII-B-15 Composition of Milk as Explained by Rumen Fermentation Parameters, Diet Composition and Combination

Abstract Although individual studies on the milk component responses to diet and rumen fermentation parameters, notably rumen pH, have identified relationships, these have not been widely summarized. Therefore, a meta-analysis was conducted with the objective of evaluating how milk fat and protein percentage change in response to diet (D), rumen fermentation parameters (R) and combination of both (R+D) variables. A secondary objective was to evaluate how these models differed when considering interactions with rumen pH. Rumen fermentation parameters included total volatile fatty acid (VFA) concentration, molar proportions of major and minor VFA, rumen pH and ammonia nitrogen, and diet variables included dry matter intake (DMI) dietary percentages of dry (DM) and organic matter (OM), crude protein (CP), neutral (NDF) and acid detergent fiber (ADF), ether extract, and starch. The database consisted of 138 published articles. Models were derived using a mixed linear regression weighted by the inverse of the standard error. Models were compared based on the concordance correlation coefficient after removing study effects (CCC). Models of milk fat based on R, R+D and R*pH+D*pH had similar capacity to explain variation within the data set (CCC: 0.26 to 0.31). Other than CP all other diet variables remained in the final D model and the same was observed in the model D*pH. Propionate was a significant variable in all R based final models along with acetate in the R*pH model and valerate in R model. Despite numerous significant relationships, ability to explain variability within the dataset was poor. All milk protein models had similar, and poor capacity to explain variability within the dataset (CCC > 0.2). Interestingly minor VFAs, valerate and iso-butyrate, were included in all R-based models. Although individual studies show precise dietary control of milk components, further work is needed to explain variability in those responses across studies.

Effects of organic loading rates on the anaerobic co-digestion of fresh vinegar residue and pig manure: Focus on the performance and microbial communities

The 70 L mesophilic semi-continuous stirred tank reactor (semi-CSTR) for co-digestion of fresh vinegar residue (FVR) and pig manure (PM) was operated for 180 days to evaluate the behavior of process stability, inhibition and recovery, as well as the succession of microbial community structures with the increasing organic loading rates (OLRs). The maximum tolerable OLR for co-digestion was determined to be 5.0 g-VS/(L·d), achieving an average methane yield (MY) of 233.77 mL/g-VS. The feeding was paused for 7 days due to the accumulation of volatile fatty acids (VFAs), and then recovered at 5.5 g-VS/(L·d) with the maximum MY of 230.09 mL/g-VS. Meanwhile, the effect of OLRs on the microbial community was analyzed. It showed that there is a significant correlation between most of the major bacteria and VFA. PCA showed that stopping feeding and reducing OLR could change the bacterial community, but not archaeal community. The aceticlastic Methanosaeta was dominant at stable stage, and gradually replaced by the hydrogenotrophic methanogen, leading to the accumulation of acetate with increasing OLR. In the recovery stage, Methanosarcina became dominant to utilize the residual acetate. Due to the vigorous aceticlastic pathway of methanogenesis, the hydrogenotrophic pathway was depressed and the H2 pressure increased, causing the accumulation of propionate in a short time. With the relative abundance of Methanosarcina increasing constantly, the VFA except propionate decreased, suggesting that Methanosarcina transformed acetate and hydrogen into methane during the recovery stage.Supplementary Material_V4.doc

Effect of salinity and surfactant on volatile fatty acids production from kitchen wastewater fermentation

Effects of the various concentrations of salt (0.5–12 g/L NaCl), surfactants (0.005–0.12 g/L LAS), and their co-presence on fermentative volatile fatty acids (VFAs) production from kitchen wastewater were investigated. VFAs production declined by 17–84% with increasing salt concentration from 3 to 12 g/L, whereas it was enhanced by 10–25% at surfactant concentrations of 0.03–0.12 g/L. The addition of 0.06 g/L surfactants in kitchen wastewater marginally improved VFAs production in different salt amended (0.5–12 g/L) reactors. Acetate and propionate were the major VFAs under all conditions; however, the percentage of propionate increased by 15–22% with increasing surfactant concentration. Higher alpha diversity indices values of the bacterial population were noted in the reactors amended with surfactant. Enterobacteriales were the dominant order of bacteria present in the reactor amended with 6 g/L of salt, whereas Lactobacillales were most prominent in reactor amended with 0.06 g/L of surfactant.

Solid and Soluble Organic Compounds Changes During Thermophilic Aerobic Digestion of Sewage Sludge

Over the past decade, thermophilic aerobic digestion (TAD) has been considered a practical approach to treating highstrength wastewater because of its several advantages. In this study, batch-mode TAD of sewage sludge was conducted using a lab-scale bioreactor to evaluate the changes in solid and soluble organic compounds. The TAD process achieved rapid degradation of the solid compound at 55oC. The removal efficiency of volatile suspended solids (VSS) increased rapidly at the early operation stage and achieved 25% at 48 h. Then, the VSS removal efficiency increased gradually up to approximately 40% at the end of the digestion (168 h). As a result of VSS degradation, the soluble chemical oxygen demand (SCOD) increased significantly up to 12 g/L at 36 h and then showed a slow decline pattern. Furthermore, the pattern of protease activity was similar to that of the SCOD. This result indicates that the rapid degradation of VSS is highly linked to the increase of protease activity and thermophilic conditions. This study used acetic acid and propionic acid. The variation patterns were similar under both acetic acid and propionic acid. The concentrations of acetic acid and propionic acid rapidly increased up to 3.05 g COD/L at 48 h and 2.51 g COD/L at 36 h, respectively. Then, major volatile fatty acids concentrations declined sharply and became undetectable after 144 h. Similar to the SCOD variation pattern, the soluble total nitrogen and NH4+-N also decreased sharply after 72 h. This might be because ammonia stripping is enhanced by pH rising and continuous aeration during the TAD.

Multivariate analysis on the evolution of flavor-related chemical contents during three-years ripening of Pixian doubanjiang

Following the ripening process of Pixian doubanjiang (DBJ), the evolution of flavor-related chemical contents impacts the maturing of flavor. During three stages of DBJ ripening: initial mature (IM), mature and deep mature (DM), 75 flavor-related chemical variables from the major volatile components (VCs), organic acids (OAs), sugars, fatty acids (FAs) and free amino acids (FAAs) were included for multivariate analysis. Twenty VCs, 6 OAs, 6 FAAs, 2 sugars and 1 FA flavor-related variables were identified as discriminative features between IM and mature stage, while 17 VCs, 17 FAAs, 7 sugars, 2 OAs and 1 FA distinguished between the mature and DM stages. Ten key variables were obtained, five each from the mature and DM stages. Sucrose could be a potential index to discriminate the DM of DBJ from the other two stages. This study may help improve the process and quality control of DBJ manufacturing.

Acidogenic phase anaerobic digestion of pretreated sugarcane filter cake for co-digestion with biogas effluent to enhance the methane production

This study aimed to evaluate the possibility of acidogenic phase as the pretreatment method of filter cake (FC) before being co-digested with biogas effluent (BE), and anaerobic sludge (AS) for methane production. The effects of separation of acidogenic and methanogenic phases on the improvement of the methane production process from a co-digestion of FC with BE, and AS were also investigated. FC was pretreated through acidogenic phase anaerobic digestion (AD) using a different substrate to inoculum ratios (SIRs) and substrate concentrations. The optimum conditions for acidogenic phase AD of FC were SIRs of 4:1 and substrate concentration of 15.0% total solid (TS). Resultantly, the maximum volatile fatty acids (VFA) yield of 0.17 g-VFAs/g-VS (volatile solids) was obtained. The major VFA components were butyric and acetic acid. The acidogenic phase of FC was semi-continuously conducted in a continuous stirred tank reactor (CSTR) at various hydraulic retention time (HRT). The highest concentration and yield of VFAs of 7.29 g/L and 0.39 g-VFAs/g-VS, respectively, were observed at HRT of 5 d. The major VFAs observed were butyric acid (48.8%), and acetic acid (36.8%). Subsequently, the proportions of pretreated FC, BE, and AS to produce methane were optimized in batch experiments. The highest methane yield (MY) of 195.9 mL-CH4/g-VS was achieved at the proportions of pretreated FC and BE of 37.75 and 22.25 g-VS/L, respectively, without the addition of AS. The optimum substrate proportion was further used to determine the MY in a 10 L CSTR with the various HRT. The maximum MY of 130.5 mL-CH4/g-VS was achieved at an HRT of 20 d which produced an EY of 4.7 kJ/g-VS. Analysis of microbial community by 16S rRNA amplicon sequencing on an illumination platform indicated that genera Rummeliibacillus, Lactobacillus, and Bacillus were the dominant bacteria found in the acidogenic phase. Methanoculleus and Methanosarcina were found to be the most dominant genera in methane fermentation. Results suggested that acidogenic phase digestion can be used as an alternative method for FC pretreatment to improve methane production. Furthermore, the separation of acidogenic and methanogenic phases improves the process stability.

Dietary supplementation of alpha-lipoic acid mitigates the negative effects of heat stress in broilers.

Heat stress accounts for substantial economic loss in the poultry industry by altering the health and performance of chickens. Alpha-lipoic acid (ALA) is a water and fat-soluble antioxidant which is readily absorbed from the intestine resulting in maximum bioavailability. Moreover, ALA acts as a coenzyme in glucose metabolism and helps generate other antioxidants. Considering these benefits, we hypothesized that dietary supplementation of ALA would help mitigate heat stress in poultry. A total of 72 Day-old broiler chicks were randomly assigned into three treatment groups: no heat stress (NHS), heat stress with basal diet (HS), and heat stress with alpha-lipoic acid (HS+ALA); each treatment group had 6 replicate pens with 4 birds in each pen (n = 24/group). The allocated birds were raised under standard husbandry practices for 3 weeks. After 21 d, birds in the HS and HS+ALA groups were exposed to heat stress (33°C for 8 hours during the day) for 3 weeks, while the NHS group was reared under normal conditions (22-24°C). The HS+ALA group received a basal finisher diet fortified with ALA (500 mg/kg) during the treatment period (22 to 42 d), while other birds were provided with the basal finisher diet. Weekly body weight and feed intake were recorded. The cecum digesta for volatile fatty acids (VFAs) analysis and 16S rRNA sequencing for the gut microbiota analysis; and the ileum tissue samples for histological and gene expression analyses were collected on d 42. Exposure to heat stress decreased (P<0.05) average daily gain (ADG) and final body weight (FBW) in the HS group compared to the NHS group, the supplementation of ALA improved (P<0.05) ADG and FBW in heat-stressed birds. Furthermore, birds in the HS+ALA group had increased (P<0.05) expression of HSP90, PRDX1, GPX3, SOD2, OCLN, and MUC2 genes and higher (P<0.05) concentrations of major VFAs (acetate, propionate, and butyrate). The dietary ALA supplementation also improved the villus height and villus height to crypt depth ratio in the HS+ALA group. The microbial diversity analysis revealed significant abundance (P<0.05) of beneficial bacteria Lactobacillus and Peptostreptococcaceae in the cecum of the ALA group. These results indicate that dietary ALA supplementation effectively mitigates the negative effects of heat stress in broilers by improving the expression of heat-shock, tight-junction, antioxidants, and immune-related genes in the intestine, improving villus structures, increasing concentration of major VFAs, and enriching the beneficial microbiota.

Bio-Valorization of Physical and Chemical Pretreated Switchgrass on Volatile Fatty Acid Production

The suitability of biomass system depends on products recovery from the waste. Switchgrass was the most renewable biomass sources and selected as feedstock for the volatile fatty acid production from anaerobic digestion. The five kinds of pretreatments involving physical and chemical treatment such as thermal, hot water, acid, alkaline and organosolv pretreatment were investigated. This study explored the characteristics of Volatile Fatty Acid (VFA) production from pretreated switchgrass compared with raw biomass. The major VFA compounds are acetic acid, propionic acid, butyric acid, iso-butyric acid and iso-valeric acid and hexanoic acid produced during digestion. The result showed that acetic acid concentration yields higher with other compounds of VFA.

A Knowledge-Driven Network-Based Analytical Framework for the Identification of Rumen Metabolites.

Metabolites are the final production of biochemical reactions in the rumen micro-ecological system and are very sensitive to changes in rumen microbes. Nuclear magnetic resonance (NMR) spectroscopy could both identify and quantify the metabolic composition of the ruminal fluid, which reflects the interaction between rumen microbes and diet. The main challenge of untargeted metabolomics is the compound annotation. Based on non-linear and linear associations between microbial gene abundances and integrals derived from NMR spectra, combined with knowledge of enzymatic reaction from the KEGG database, this study developed a knowledge-driven network-based analytical framework for the inference of metabolites. There were 89 potential metabolites inferred from the integral co-occurrence network. The results are supported by dissimilarity network analysis. The coexistence of non-linear and linear associations between microbial gene abundances and spectral integrals was detected. The study successfully found the corresponding integrals for acetate, butyrate and propionate, which are the major volatile fatty acids (VFA) in the rumen. This novel framework could very efficiently infer metabolites to corresponding integrals from NMR spectra.

VOLATILE FATTY ACIDS FROM ORGANIC WASTES AS NOVEL LOW-COST CARBON SOURCE FOR Yarrowia lipolytica

Microbial oil biosynthesis is envisaged as a promising technology for sustainable production of chemicals and fuels. Sugar-based substrates are the most typical carbon sources used for this purpose where metabolic pathways and stoichiometry are well known. However, the use of low-cost substrates is crucial for the economic viability of the process. Volatile fatty acids (VFAs) are considered to be a novel low-cost carbon source for microbial lipid production. They can be utilized by oleaginous yeasts to produce and store fatty acids in form of intracellular lipid bodies. In this work, Yarrowia lipolytica growth and substrate consumption were evaluated using the major VFAs present in anaerobic effluents. Individual VFAs as well as synthetic mixtures were tested at different concentrations to determine uptake rates and potential toxicity. Increasing VFA chain length resulted in greater biomass yield although, when added individually, 4 g Carbon/L VFA (e.g. 6.45 g/L of caproic and 10 g/L of acetic acid) caused inhibitory effects. Remarkably, biomass growth increased by 2.5-fold on real anaerobic fermentation effluent compared with synthetic mixtures. When real digestate was supplemented with synthetic VFAs up to 26.5 g/L, the inhibitory effect of the acids was counterbalanced. The results provided evidence of robustness of Y. lipolytica towards low-cost fermentation effluents and present this yeast as a promising candidate for the sustainable production of microbial oil using real digestates.

Higher load operation by adoption of ethanol fermentation pretreatment on methane fermentation of food waste

The study aims to examine whether ethanol fermentation pretreatment (EP) of food waste can contribute to high load operation on methane fermentation using an anaerobic membrane bioreactor (AnMBR). The hydraulic retention time was reduced stepwise from 20 to 5 days to increase the load by increasing the feeding volume. The corresponding organic loading rate (OLR) ranged from 6.6 to 26.5 g-COD/L/day. The control series (without pretreatment) was operable to an OLR of 8.8 g-COD/L/day versus 26.5 g-COD/L/day for the EP series. In the control series, the major volatile fatty acid (VFA) produced by acidogenesis in the reactor was propionic acid because based on Gibbs free energy variations for the methane conversion, acetic acid conversion was not as easy as from propionic acid as from ethanol in the EP series. EP proved effective in avoiding VFA accumulation and subsequent decreased pH. Therefore, EP significantly improves AnMBR performance.

Effect of shear velocity and feed concentration on the treatment of food waste in an anaerobic dynamic membrane Bioreactor: Performance Monitoring and microbial community analysis

The formation of the dynamic membrane (DM) in an anaerobic dynamic membrane bioreactor (AnDMBR) treating food waste was, previously, found to be beneficial to the stable performance of an anaerobic digestion system. This study examines the effect of shear velocity and feed concentration on the performance and microbial community of an AnDMBR treating food waste. The shear velocity was varied from 0.04 to 1.74 m/h, using three different feed concentrations (50, 80, and 100 g-COD/L). The highest average methane production rate of 2.6 L-CH4/L/d was achieved at a feed concentration and shear velocity of 100-g COD/L and 0.34 m/h, respectively. Increasing shear velocity, within certain limits, is beneficial to AnDMBR systems, promoting better mixing, substrate-biomass interactions, and DM layer formation. Methanosarcina flavescens proliferated (69%) at high shear velocities when acetic acid was the major volatile fatty acid. The abundance ratio between Bacteroidetes and Firmicutes showed a linear relationship to methanogenic performance.

PSVII-6 Effects dietary herbal vitamin E on lamb performance, ruminal fermentation, blood biochemical profile, and meat oxidative stability

Abstract The objective of this experiment was to evaluate four levels of a natural vitamin E on lamb performance, blood metabolites, rumen metabolism and meat quality characteristics. Thirty-six male lambs (29.24 SD 2.54 kg Hampshire x Suffolk) were used in a completely randomized experimental design. Treatments consisted of dietary inclusion of Herbal E-50 (Nuproxa) at 0, 1, 2 and 3 g/kg dry matter (DM) for for 60 days in lambs that did not receive any additional source of vitamin E. A quadratic response was observed on daily gain, final body weight, feed conversion, intake blood cholesterol and glucose. The estimated optimal level of herbal E obtained of herbal E levels for average daily gain was 1.76 ± 0.10 g/kg and 1.84 ± 0.77 g/kg for feed conversion. Ruminal pH and the major volatile fatty acids were not affected by herbal E. A quadratic response was observed on blood cholesterol (P &lt; 0.10) and glucose (P &lt; 0.01). Dietary herbal E increased linearly counts of erythrocytes (P &lt; 0.05), platelet (P &lt; 0.10), proteins and globulins (P &lt; 0.01) whereas the albumin/globulin ratio was linearly reduced (P &lt; 0.01). Meat texture was improved (quadratic; P &lt; 0.05) and the reducing/antioxidant capacity was improved linearly (P &lt; 0.001) with herbal E. Redness measured at 7 d was also improved with herbal E (P &lt; 0.05; lineal effect). The lamb performance can be improved with 1.8 g/kg Herbal E 50 in finishing lamb diets. The inclusion of herbal E feed plant additive improved the daily gain in finishing lambs, feed efficiency and improved meat oxidative stability.

Spatial distribution of major bacterial species and different volatile fatty acids in a two-phase anaerobic biofilm reactor with PVA gel beads as bio-carrier

Conventional completely mixed anaerobic treatment systems limit the chances of the different species of bacteria to spatially group together according to their mutual cooperation and as a result, show a lower efficiency and vulnerability towards shock situations. It is interesting to know about the stratification of the different bacterial species participating in the degradation process and the intermediates that they produce. In this study, we established and optimized a two-phase anaerobic packed bed biofilm reactor system (AnPBR) with porous PVA gel beads used as bio-carriers and ran the reactor system in a steady state to observe the VFAs produced along with the microbial diversity of the predominant species at different stages of the reactor system. We observed that acetate and butyrate were the predominant intermediate VFAs while concentrations of other VFAs such that propionic acid were low. Acetobacterium and Clostridium were found to be the most abundant bacterial species in acidogenic reactor while methanogenic reactor was highly enriched with Methanobacterium and Methanosarcina. Apart from the above, syntrophic populations such as Syntrophobactor wolinii were also observed to be dominant in both the reactors – especially towards the end of acidogenic reactor and the initial part of the methanogenic reactor.