Volatile Fatty Acid Values Research Articles

Lysinibacillus fusiformis: a novel fibrolytic native strain from the rumen microbiome that increases in vitro digestibility of central agricultural residues

ABSTRACT Increasing the digestibility of agricultural residues is one goal of sustainable livestock production, and the role of rumen microbiome-feed interaction is critical for efficient digestion. This study was aimed at isolating and evaluating in vitro the effect on dry-matter digestibility (IVDMD), relative feed values (RFV), volatile fatty acid (VFA) synthesis, pH changes, and gas production (GP) by the inclusion of native rumen strains in mixtures of corn, sorghum, and oat agricultural residues with ruminal fluid. The results show that an inoculum of 1 × 1010 colony-forming unit per millilitre (CFU/mL) of the aero-tolerant native rumen strain Lysinibacillus fusiformis increases the IVDMD, RFV, and VFA values of all mixtures. During agricultural residue fermentation, the pH was stable, and propionic acid was the primary fatty acid synthesized, indicating increased energy availability for efficient cattle growth performance while limiting molecular hydrogen (H2) synthesis for conversion to methane (CH4). These results suggest that L. fusiformis could be used as a direct-feed microbial to promote sustainable livestock production. To the best of our knowledge, this is the first report to link the fermentation of fibrous agricultural residues in ruminal fluid inoculated with a fibrolytic native strain and digestibility in favour of increasing the efficiency of livestock production.

Silage Quality, Nutrient Content and Relative Feed Value of Urea and Molasses Added Sweet Maize [Zea mays (L.) saccharata Sturt.] Silage

Background: This study was carried out to determine silage quality, nutrient content, relative feed value (RFV), fermentation parameters and Fleig scores of sweet maize [Zea mays (L.) saccharata Sturt.] without the cob ensiled with urea or molasses. Methods: Plant parts remaining from the sweet maize whose cobs were harvested were ensiled with the addition of 1% urea and 5-10% molasses. In the liquid samples collected from the silages, pH values, ammonia nitrogen (NH3-N) and volatile fatty acid (VFA) concentrations were measured and the silage samples were subjected to crude nutrient analyses, RFV and Fleig score determination. Result: Significant differences were found among the groups in terms of their dry matter (DM), organic matter (OM), crude ash (CA), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) values. The difference between silage groups was significant in terms of NH3 and VFA values. In the analyses of Fleig scores, physical parameters and RFV results, the groups were found significantly different except for Fleig scores. In parallel with the increase in the concentration of urea used in the silage groups, there were reductions in Fleig scores, physical parameters and RFV values, while their CP levels increased. The molasses that was added to the silages led to a reduction in their silage pH, NH3-N and butyric acid (BA) values and an increase in their lactic acid (LA) values. It was concluded that the additives used in this study contributed positively to the quality of the silages, all silages with additives were quality silages and they could be used as an alternative quality roughage resource in feeding ruminants.

Production of biogas from coffee husk waste with rumen fluid and mixture of rumen fluid and cow dung

Coffee is the second largest traded commodity in the world and also produces by-products and residues. Coffee husk waste is an abundant lignocellulosic material and has the potential to be used as raw material for biogas production. This study compared the production of biogas from coffee husk using rumen fluid with a mixture of rumen fluid and cow dung. In the pretreatment process using ethanol, the waste consisted of 65.90% cellulose, 24.95% hemicellulose, 0.21% lignin, 2.16% pectin, 1.08% protein, 3.11% tannins, 0.91% caffeine, and 3.78% polyphenols. The decrease in TS (total solid) and VS (volatile solid) values for C-RC (coffee-rumen fluid-cow dung) was greater than for C-R (coffee-rumen fluid) as 32.20% and 42.47% were obtained for C-RC, while the values for C-R were 19.32% and 38.37 The VFA (volatile fatty acids) values for C-R and C-RC were 1.09% and 2.24%. The biogas produced for C-R was CH4 of 14.4%, CO2 of 13.75%, and H2 of 0.59%, while that for C-RC consisted of CH4 of 22.3%, CO2 of 4.11%, and H2 of 0.36%. The yield of biogas for C-R was 0.48 Nm3/(kg COD removal) and for C-RC was 1.95 Nm3 /(kg COD removal).

Mathematical Modeling for Evaluating the Sustainability of Biogas Generation through Anaerobic Digestion of Livestock Waste

The paper investigates the mathematical modeling of anaerobic fermentation for the utilization of animal wastes. It analyzes various approaches to the mathematical modeling of anaerobic digestion processes. However, most of the models previously proposed do not take into account a number of key parameters such as the levels of micro and macronutrientls (such as K, Na, Ca, Mg, Mo, etc.), values of volatile fatty acids, C/N ratio, pH levels, extent of grinding, moisture, and others. This paper proposes a new mathematical model of anaerobic fermentation under industrial scale conditions. The model was developed on the basis of regression analysis and correlation. It found empirical relationships between biogas yield and 26 different parameters. These parameters are measured by appropriate biosensors in industrial production. Some of them have more significant influence on the fermentation process than others. Overall, the developed mathematical model has the potential to provide useful insights into biogas production and can be used to optimize anaerobic fermentation processes.

Bio-processing Plantation by-products with White Oyster Mushroom (Pleurotus ostreatus) to Improve Fermentability and Digestibility Based on Substrate Type and Fermentation Time

Plantation by-products can be used as livestock feed with proper processing, optimizing the feed efficiency of palm kernel cake (PKC), empty oil palm bunch (EOPB), and acacia sawdust (AS). This study aimed to improve the usability of the byproducts as alternative feed through the Pleurotus ostreatus fermentation process. To this end, a 3×3 factorial, completely randomized design was applied. Factor A was the type of substrate, P1 = PKC, P2 = EOFB and P3 = AS. Factor B was the fermentation period, T1 = 0 d, T2 = 30 d and T3 = 60 d. The collected data were analyzed using analysis of variance (ANOVA), and the significantly different result was further tested using Duncan Test. The observed variables include Neutral Detergent Fiber (NDF), acid detergent fiber (ADF), hemicellulose, pH value, dry matter digestibility (DMD), organic matter digestibility (OMD), N-NH 3 , and volatile fatty acids (VFA). The study result showed that P.ostreatus mushroom in various substrate types did not significantly affect the fiber fraction of NDF, ADF, and Hemicellulose. This study also found that the interaction of substrate type and fermentation duration significantly affects dry matter digestibility, organic matter digestibility, N-NH 3 production, and VFA values. This study concluded P. ostreotus increased the nutritional value and digestibility of the by- product from plantation processing. The best fermentation duration was 60 d PKC was found to have the highest digestibility value, and the best interaction was found in PKC with 60 d of fermentation.

Fermented Total Mixed Ration with Cottonseed Meal or Rapeseed Meal Improved Growth Performance and Meat Quality of Hu Lamb Compared to Total Mixed Ration with Soybean Meal

Protein sources in livestock feed include cottonseed meals (CSM) or rapeseed meals (RSM). However, their use in feed diets is restricted due to anti-nutritional elements such as free gossypol or glucosinolate. The main objective of this study was to determine the effect of microbial fermentation of total mixed ration (TMR) with CSM/RSM on the growth performance and meat quality of Hu lamb. Fifty-one male Hu lambs (4 months old) with a 22.51 kg body weight were randomly assigned to three treatments and fed unfermented TMR with soybean meal (control group), FTMR (fermented total mixed ration) with CSM or RSM, respectively. The experiment lasted 97 days. Growth performance, rumen fermentation, and meat quality were measured. Overall dry matter intake (DMI), average daily gain (ADG), and final body weight (FBW) were similar among treatments (p > 0.05). There were no significant differences in the lightness (L*), redness (a*), and yellowness (b*) of longissimus thoracis (LT) muscle meat. There were no significant differences between the FTMR-CSM/RSM and control groups in drip loss, cooking loss, cooking percentage rate, or shear force of LT muscle meat. Lambs fed FTMR-CSM had significantly higher rumen fluid total volatile fatty acid values than those in control or FTMR-RSM groups (p < 0.05). Meat from lambs fed FTMR-RSM had a higher level of saturated fatty acids than lambs fed the control diet. The LT muscle meat of lamb fed FTMR-CSM had more unsaturated fatty acids than the control group (p < 0.001). In conclusion, FTMR with cottonseed or rapeseed meal can be fed without causing any adverse effects on Hu lamb.

Effects of freeze‐dried black carrot fiber addition on the physicochemical, color, sensory attributes, and mineral contents of ayran

The present study was conducted to evaluate the production of ayran by adding freeze-dried black carrot fiber at different ratios (0%, 0.25%, 0.5%, and 1%), followed by its storage for 14 days. It turned out that the more the amount of black carrot added, the more the amounts of Na, Mg, K, and Ca, though the sensory scores decreased. While pH, titratable acidity, viscosity, whey separation, and acetaldehyde contents of ayran were not affected by black carrot addition (p > .05), water-holding capacity, volatile fatty acids, L*, a*, and b* values appeared to be significantly affected (p < .05). The highest and lowest a* values were determined on the 1st (A1: 7.09) and 14th (C: −1.24) days, respectively. Higher L*, b*, and volatile fatty acid values were found in the ayran sample containing 0.25% black carrot fiber (A1) following the control samples. Apart from the water-holding capacity of ayran, no significant change occurred in other properties during storage (p > .05). The highest water-holding capacity was observed in A2 (19.53%) on the 14th day of storage. The ayran-containing 0.25% black carrot fiber presented the best results. Fortification of ayran with black carrot fiber is likely to make a significant contribution to the diversification of functional dairy products. Novelty impact statement Freeze-drying of black carrot will enable to obtain rich color substances in its composition, reduce transportation, and storage costs, and provide a product with a longer shelf life. This study has aimed to increase the consumption of high-fiber black carrot, which is freeze-dried and powdered, by adding it into ayran, and to benefit from the rich nutritional content of black carrot, as well as developing a natural, nutritious, and highly appealing product for consumers. As a consequence, an important contribution will be made to the product diversification in the dairy industry. The functional properties that black carrot will bring to ayran will ultimately benefit public health.

The application of total mixed ration with iso protein and different TDN levels on the productivity of Simmental crossbred cattle

The objective of research was to know the levels of digestibility and fermentability between breeders feed and iso-protein-based feed. A randomized Complete Design with 5 treatments and 4 replications based in the iso-protein with different levels of Total Digest Nutrient (TDN) was employed. Research on amber hay and concentrate combined into “Complete Feed” was conducted. The treatment with T0 = Complete feed (6% CP+ 60% TDN), T1 = Complete (12% CP+ 60% TDN), T2 = Complete feed (12% CP+63% TDN), T2 = Complete feed (12% CP+ 66% TDN) and T4 = Complete feed ((12% CP+ 69% TDN) was given. The parameters observed were dry matter digestibility (DMD), organic matter digestibility (OMD), volatile fatty acid (VFA), NH3, dry matter intake, CP intake, TDN intake, daily weight gain (DWG), and feed efficiency. The result of complete feed application on Simental Crossbreed Intake of DM T0 and T2 was significantly different, but the CP intake and DWG was not significantly different. TDN intake, conversion, and feed efficiency of feed T0 to all treatments were significantly different (P <0.05). Feeding is recommended using CP 12% and TDN 63% (T2). The results showed that vitro feed analysis was not significantly different (P> 0,05%) in terms of DMD, OMD, NH3 and VFA values.

Impact of Olive Cake Supplementation on some Properties of Bio-Labneh Made from Goat’s Milk

The aim of this study was to investigate the effect of incorporation of olive cake (OC) on some properties of Labneh made from goat's milk using ABT-5 culture. Three rates of OC (0.25, 0.50 and 1 %) were added to both goat's milk and Labneh paste. Labneh was stored for 28 days at 5°C and samples were taken and analysed at 7 days intervals. Adding OC increased pH, total solids, fat , salt, total protein, total phenol, dietary fibers, total antioxidant activity and total volatile fatty acids values. On contrary, titratable acidity, water soluble nitrogen, and total bacterial count, lactic acid bacteria and bifidobacteria contents slightly decreased. Sensory evolution scores revealed that the Labneh fortified with 0.25 and 0.50% OC (added to milk or paste) was acceptable during the storage period. Adding OC depress production cost of Labneh. Thus, diverse nutritional and economic benefits can be acquired.

Calidad fermentativa y producción de metano en ensilados de rastrojo de maíz adicionados con nopal fermentado y sin fermentar

The objetive of this research was to evaluate the nutritive and fermentative quality and methane emissions in corn stover silages with nopal (Opuntia ficus-indica), for which three experimental treatments were evaluated, T1: corn fodder; T2: 75 % corn stover + 25 % nopal; and T3: 75 % corn stover + 25 % fermented nopal. Twenty-one micro-silos (7 per treatment) were prepared in plastic containers and left to ferment for 30 days. At the end of fermentation, the chemical composition, fermentation parameters, gas production and methane (CH4) were evaluated. Dry matter (DM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents were different among treatments (p<0.05); CP content increased 44 % with the addition of fermented cactus (T3). Ammonia nitrogen, lactic acid and volatile fatty acids values were different among treatments (p<0.05). Maximum gas production (Gmax) and CH4 concentration decreased 32 % and 49 % at T3, respectively. The addition of cactus and fermented cactus to corn stover silage increases protein content. In addition, it reduces ruminal methane synthesis in vitro.

Effect of Cyclotrichium niveum Essential Oil on Rumen Microbial Fermentation and in vitro Digestibility of Barley

The digestibility of feed in ruminants and the volatile fatty acids (VFA) resulting from digestion directly affect animal performance. It has long been studied on the use of essential oils as an alternative to antibiotics to ensure optimum conditions for the rumen environment. Cyclotrichium niveum (mountain mint) essential oil is rich in antimicrobial agents. In this study different doses (0, 50, 100 and 150 mg/L of culture fluid) of Cyclotrichium niveum essential oil was incubated 24 hours with barley in diluted ruminal fluid takes from fistulated cows fed with a 40:60 concentrate:forage diet in order to assess the effects on rumen microbial fermentation and in vitro true digestibility of barley. True digestibility of barley was determined in ANKOM Daisy Incubator. All doses of Cyclotrichium niveum significantly (P&amp;lt;0.001) decreased the in vitro dry matter (DM), organic matter (OM), neutral detergent fiber (NDF) digestibility of barley. Cyclotrichium niveum essential oil negatively affected end-products of rumen fermentation; the value of the measured rumen volatile fatty acids (VFA: acetate, propionate, butyrate, isobutyric acid, valerate and isovalerate) significantly decreased compared to the control group (P&amp;lt;0.001). Carbon dioxide and methane gases created as a result of incubation in rumen fluid were calculated using volatile fatty acid values formed in rumen fluid. The addition of Cyclotrichium niveum essential oil significantly reduces the CO2 in rumen fluid (P&amp;lt;0.001). Methane (CH4) gas from rumen fluid was significantly decreased in treatment groups compared the control group (P &amp;lt;0.001) While end-products of rumen fermentation parameters significantly decreased with all doses of Cyclotrichium niveum essential oil, rumen pH has increased (P&amp;lt;0.05). The results show that when the Cyclotrichium niveum essential oil incubated with barley significantly inhibited the rumen microbial activity and overall fermentation process of rumen.

Data-driven techniques for fault detection in anaerobic digestion process

Anaerobic digestion (AD) is an appropriate process for bio-energy (biogas) production from waste and wastewater receiving a high level of attention at both academic and industrial scale due to increasing public awareness regarding environmental protection and energy security. Monitoring such processes is an imperative task to ensure optimized operation and prevent failures and serious consequences during the operation of the plant. To fulfill this task, a practical data-driven framework for fault detection in AD is proposed and validated on a simulated data set obtained using the benchmark simulation model No.2 (BSM2) from the International Water Association (IWA). The proposed framework is based on data-driven soft-sensors predicting total volatile fatty acids (VFA), mainly consisting of acetate, propionate, valerate and butyrate concentrations inside the digester. The VFA concentration is considered because it does not only reflect the current process health, but it is also sensitive to the incoming feeding imbalances. VFA soft-sensors using different advanced techniques such as support vector machine (SVM), extreme learning machine (ELM) and ensemble of neural network (ENN) are tested and compared in terms of accuracy and fault detection (FD) robustness. A principal component analysis (PCA) model was also developed to compare the proposed approaches with the traditional FD method. By applying soft-sensors, the residual signal, i.e., the difference between estimated and measured VFA values can be generated. This residual signal can then be used in combination with univariate statistical control charts to detect the faults. A comparison of the proposed FD framework with PCA method clearly demonstrates the over performance and feasibility of the proposed monitoring framework.

Variation of Fatty Acids and Antioxidants Contents of Vegetarian Rayeb Milk as Affected by Fortification with Natural and Artificial Sweeteners

Rayeb milk (bio-stirred yogurt) samples were prepared from cow milk sesame milk or cow and sesame milk mixture (1:1) with or without adding sucrose (5%), honey (5%), fructose (2.5%) and sorbitol (1.5%) and using ABT-5 culture. Results showed levels of saturated fatty acids (SFA), short chain fatty acids (SCFA) and medium chain fatty acids (MCFA were lower whereas values of unsaturated fatty acids (USFA), monounsaturated fatty acids (MUSFA), polyunsaturated fatty acids (PUSFA) and long chain fatty acids (LCFA) were higher in sesame milk Rayeb than that of Rayeb manufactured from cow milk. Rayeb made from cow and sesame mixture had higher levels of antioxidant activity than Rayeb prepared from cow milk or sesame milk. The acidity, total solids and total volatile fatty acids values of Rayeb milk treatments contained sweeteners were higher than that of control. The addition of sweeteners decreased SFA, SCFA and MCFA and increased USFA, MUSFA, PUSFA, LCFA and antioxidant activity values of Rayeb milk. Essential fatty acids, linoleic acid (omega-6), α-linolenic acid (omega-3) and oleic acid (omega-9) greatly increased in Rayeb made from cow and sesame milk mixture. Adding sweeteners had the same effect. Fortification of Rayeb milk with sweeteners highly improved the smell, taste, mouth feel, texture and body evaluation scores.

Robust Data-Driven Soft Sensors for Online Monitoring of Volatile Fatty Acids in Anaerobic Digestion Processes

The concentration of volatile fatty acids (VFAs) is one of the most important measurements for evaluating the performance of anaerobic digestion (AD) processes. In real-time applications, VFAs can be measured by dedicated sensors, which are still currently expensive and very sensitive to harsh environmental conditions. Moreover, sensors usually have a delay that is undesirable for real-time monitoring. Due to these problems, data-driven soft sensors are very attractive alternatives. This study proposes different data-driven methods for estimating reliable VFA values. We evaluated random forest (RF), artificial neural network (ANN), extreme learning machine (ELM), support vector machine (SVM) and genetic programming (GP) based on synthetic data obtained from the international water association (IWA) Benchmark Simulation Model No. 2 (BSM2). The organic load to the AD in BSM2 was modified to simulate the behavior of an anaerobic co-digestion process. The prediction and generalization performances of the different models were also compared. This comparison showed that the GP soft sensor is more precise than the other soft sensors. In addition, the model robustness was assessed to determine the performance of each model under different process states. It is also shown that, in addition to their robustness, GP soft sensors are easy to implement and provide useful insights into the process by providing explicit equations.

INDICATORS OF VOLATILE FATTY ACIDS IN DIFFERENTIAL DIAGNOSTICS OF INFECTED AND STERILE PANCREONECROSIS

The aim of the study was to assess the information content of volatile fatty acid parameters for the differential diagnosis of infected and sterile pancreatic necrosis. The work is based on the results of examination and treatment of 34 patients with pancreatic necrosis. The analysis of concentrations of volatile fatty acids: acetic, propionic, butyric and isovaleric was carried out on an automated gas chromatograph «Crystallux-4000» with a capillary column «HP-FFAP» and flame ionization detector. The indicators of acetic, propionic, butyric, isovaleric acid and the sum of volatile fatty acids are statistically significantly higher in patients with infected pancreatic necrosis compared with the indicators of volatile fatty acids in patients with sterile pancreatic necrosis. Volatile fatty acid values can be used for the differential diagnosis of infected and sterile pancreatic necrosis.

A comparative study of volatile fatty acids in the blood and in the drainage from pancreatic fistula in pancreatic necrosis

Relevance. The informative value of the content of volatile fatty acids (VFA) in the fistulous drainage from pancreas not been studied in the diagnosis of pancreonecrosis (PN). The informative value of the indices of the content of VFA in the blood has not been studied sufficiently in the diagnosis of PN.&#x0D; Aim of the study is to compare the content of VFA in the blood and in the fistulous drainage from pancreas in patients with pancreatic necrosis.&#x0D; Materials and methods. Samples of blood and fistulous drainage from pancreas isolated from patients with a confirmed diagnosis of PN were studied (n = 18). There was analysis of the concentrations of VFA: acetic, propionic, butyric and isovaleric acids by gas-liquid chromatography on an automated gas chromatograph "Crystallux-4000" with a capillary column "HP-FFAP" Agilent Technologies and a flame ionization detector. The anaerobic index and sum of VFA were calculated.&#x0D; Results. Higher values of the content of acetic, propionic and butyric acids, the sum of VFA and lower values of the content of isovaleric acid and anaerobic index were found in patients with PN in comparison with those of practically healthy donors. Higher values of the content of acetic, propionic and isovaleric acid, the sum of VFA and anaerobic index were noted in the fistulous drainage from pancreas in comparison with the same parameters in blood in patients with PN. The correlation of pairwise conjugated parameters of the content of propionic and isovaleric acids, anaerobic index and the sum of VFA in fistulous drainage from pancreas and blood are discovered in patients with PN.&#x0D; Conclusions. The concentration of acetic, propionic and isovaleric acids, the sum of VFA were higher in the fistulous drainage from pancreas than in the blood in patients with PN. The analysis of the parameters of the VFA can be used as additional criteria for the early diagnosis of PN.

Estimated ruminal digestion values and digestion end-products of concentrated mix feed after in vitro treatment with propionic acid

This study was aimed at determining the effects of propionic acid supplementation at doses of 0 (control group, PA0), 12, 24, 48 and 96 mM (PA12, PA24, PA48, and PA96) to concentrated mix feed on in vitro cumulative total gas production, methane emission, gas kinetics (potential gas production, (a + b)&lt;sub&gt;gas&lt;/sub&gt; and gas production rate, c&lt;sub&gt;gas&lt;/sub&gt;), estimated digestibility, estimated energy value and the end-products and variables of in vitro digestion (total bacteria count, the number of ciliate protozoa, volatile fatty acids, pH value and ammonia-N). Digestion treatments were carried out in an anaerobic in vitro fermenter for up to 96 h. The in vitro cumulative total gas production, (a + b)&lt;sub&gt;gas&lt;/sub&gt;, estimated metabolic energy, estimated net energy lactation and estimated organic matter digestibility and ammonia-N concentration were decreased by propionic acid up to 96 mM (P &amp;lt; 0.05). In the in vitro fermenter fluid, total bacteria count, the total numbers of ciliate protozoa and the individual numbers of some ciliate protozoa (Entodiniinae, Isotricha spp. and Diplodiniinae) (P &amp;lt; 0.01) decreased linearly with increasing concentrations of dietary propionic acid. The total molar concentrations of volatile fatty acids decreased in response to propionic acid supplementation (P &amp;lt; 0.001). Dietary propionic acid elicited linear increases in the molar concentrations of propionic acid (P &amp;lt; 0.001) and butyric acid (P &amp;lt; 0.01) as proportions of total volatile fatty acids of the in vitro fermenter fluid. In contrast, molar proportions of acetic acid, the c&lt;sub&gt;gas&lt;/sub&gt;, pH values and the numbers of Dasytricha sp. were not affected by dietary propionic acid supplementation (P &amp;gt; 0.05). The addition of 12–96 mM propionic acid to concentrated mix feed decreased methane emission from the rumen and negatively affected microbiota count, feed digestibility, proteolysis, and molar volatile fatty acid values in the rumen environment.

Performance of semi-continuous anaerobic co-digestion of poultry manure with fruit and vegetable waste and analysis of digestate quality: A bench scale study

Poultry manure (PM) can contain ammonium and ammonia nitrogen, which may inhibit the anaerobic process. The aim of this work was to evaluate the performance of anaerobic digestion of PM co-digested with fruit and vegetable waste. Two semi-continuous bench scale (19L) stirred tank reactors were used. The operating conditions were: 34.5 °C, 2 gVS/L.d (organic load rate), 28 d of hydraulic retention time and 100 revolutions per m (1 h × 3 times by day) for the agitation. The reactors were fed PM and a mixture of PM and fruit and vegetable waste (FVW) at equal proportions (based on wet weight). The performance of the anaerobic process was assessed through biogas and methane yields, reduction of organic matter, release of nitrogen compounds and the monitoring of stability indicators (pH, volatile fatty acids (VFA), total (TA) and partial (PA) alkalinity). Moreover, the digestate quality was evaluated to determine potential risk and benefits from its application as biofertilizer. Toxicity was assessed using Daphnia magna immobilization tests. Results showed that biogas and methane yields from PM-FVW were 31% and 32% higher than PM alone, respectively. Values of organic matter, pH, alpha (PA/TA) and VFA revealed that stability was approached in PM and PM-FVW. The co-digestion of PM with FVW led to the highest methane and biogas yields, lower FAN and TAN concentrations, and a better digestate quality compared to mono-digestion of this manure.

Determination of volatile fatty acids in digestate by solvent extraction with dimethyl carbonate and gas chromatography-mass spectrometry

Volatile fatty acids (VFAs) are among the most important parameters in process monitoring of anaerobic digestion plants for biogas production. The concentration of single VFA species is typically determined by direct injection of the acidified aqueous phase of digestate samples into GC-FID. Analysis of dimethyl carbonate extracts was investigated as an alternative method consisting of a simple and rapid in-vial procedure of acidification and solvent extraction of the sample, followed by centrifugation and GC-MS analysis. The principal figures of merit resulting from internal standard calibration were comparable to those proposed for the direct analysis of aqueous digestate, while the analysis of real samples did not provide statistically significant differences between the two methods according to parametric and non-parametric tests. Procedural aspects including sample amount and solid removal improved with dimethyl carbonate, while GC contamination was reduced. The method was applied to seventeen samples from fully operating anaerobic digesters fed with various feedstocks and enabled the individuation of high probability of system stress through the values of total VFA, propanoic acid, longer chained VFA concentrations and the ratio between acetic and propanoic acid concentrations. The use of dimethyl carbonate allowed the detection of alicyclic and aromatic acids that could represent new molecular markers in assessing the origin of feed and process conditions.

Predicting acute toxicity of traditional Chinese medicine wastewater using UV absorption and volatile fatty acids as surrogates

In this study, the applicability of UV absorbance at 254 nm (UV254) and volatile fatty acids (VFAs) to serve as reliable surrogates to predict acute toxicity of traditional Chinese medicine (TCM) wastewater was investigated. The medicine residues and VFAs were identified as main components of the TCM wastewater, and their individual and joint toxicity assays were operated with luminescent bacteria. The median effective concentration (EC50) values of medicine residues and VFAs were in the range of 26.46–165.55 mg/L and 11.45–20.58 g/L, respectively. The joint toxicity action modes of medicine residues, VFAs and medicine residues-VFAs were identified as additive, additive and synergistic respectively. UV254 and VFAs showed better correlations with acute toxicity according to the correlation analysis, compared with other conventional parameters. The regression model was a good fit for toxic unit (TU50) as a function of UV254 and VFAs according to the stepwise regression method (adjusted R2 = 0.836). Validation of the model to the pilot-scale samples provided satisfactory prediction results in the influent and hydrolysis acidification effluent samples tests, but for EGSB effluent and final effluent samples, the model needed further optimization. Surrogates prediction using UV254 and VFAs provided a valuable and cost-saving tool for rapid or on-line monitoring of acute toxicity of TCM wastewater.