A combined pig model to determine the net absorption of volatile fatty acids in the large intestine under different levels of crude fiber

Background:This study aimed to develop a combined model to quantify the net absorption of volatile fatty acids(VFA)in the large intestine(LI)of pigs.Methods:Fifteen female growing pigs(Duroc×Large White×Landrace)were ranked by body weight(30±2.1 kg)on day 0 and assigned to one of three treatments,namely the basal diet containing different crude fiber(CF)levels(LCF:3.0%CF,MCF:4.5%CF,and HCF:6.0%CF).The pigs were implanted with the terminal ileum fistula and the cannulation of the ileal mesenteric vein(IMV),portal vein(PV),and left femoral artery(LFA)from days 6 to 7.[13 C]-Labeled VFA and P-aminohippuric acid were constantly perfused into the terminal ileum fistula and the cannulation of the IMV(day 15),respectively.Blood samples were collected from the PV and the LFA during perfusion(5 h),and LI samples were collected.Results:The net flux of[12 C]-acetic acid in the PV was greater for LCF versus MCF(p=0.045),but no difference was observed in the net flux of[12 C]-propionic acid(p=0.505)and[12 C]-butyric acid(p=0.35)in the PV among treatments.The deposition of[12 C]-acetic acid in the LI was greater for LCF versus MCF(p=0.014),whereas the deposition of[12 C]-propionic acid(p=0.007)and[12 C]-butyric acid(p=0.037)in the LI was greater for LCF versus HCF.Conclusions:In conclusion,this pig model was found conducive to study the net absorption of VFAs in the LI,and LCF had more net absorption of VFAs in the LI than MCF and HCF.

Volatile fatty acids carbon source for biological denitrification

In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrification rate than single VFA C-source consisting of them. When VFA were used as carbon source, consumed carbon quantity for denitrification was closed to 1. 07 mg VFA-C/mg NO-N. About 20% of the applied C/N was used for assimilative purposes. As rising up influent C/N by increasing the C load ,the sludge yield YN increased. The part of carbon consumption increased and the effluent oxidized nitrogen decreased. At pH 7. 5, 25℃ and sludge yield 0.72 mg VSS/mg NO-N, the calculated influent VFA-C /NO critical value was 1. 43 for complete denitrification.

Impacts of the unsaturation degree of long-chain fatty acids on the volatile fatty acid profiles of rumen microbial fermentation in goats in vitro

This study investigated the impacts of the degree of unsaturation （unsaturity） of long-chain fatty acids on volatile fatty acid （VFA） profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, including stearic acid （C18：0, control group）, oleic acid （C18：1, n-9）, linoleic acid （C18：2, n-6）, a-linolenic acid （C18：3, n-3）, arachidonic acid （C20：4, n-6） and eicosapentaenoic acid （C20：5, n-3）, were tested. Rumen fluid from three goats fitted with ruminal fistulae was used as inoculum and the inclusion rate of long-chain fatty acid was at 3% （w/w） of substrate. Samples were taken for VFA analysis at 0, 3, 6, 9, 12, 18 and 24 h of incubation, respectively. The analysis showed that there were significant differences in the total VFA among treatments, sampling time points, and treatment×time point interactions （P〈0.01）. a-Linolenic acid had the highest total VFA （P〈0.01） among different long-chain fatty acids tested. The molar proportion of acetate in total VFA significantly differed among treatments （P〈0.01） and sampling time points （P〈0.01）, but not treatment×time point interactions （P〉0.05）. In contrast, the molar proportion of propionate did not differ among treatments during the whole incubation （P〉0.05）. However, for butyrate molar proportions, significant differences were found not only among sampling time points but also among treatments and treatment×time point interactions （P〈0.01）, with eicosapentaenoic acid having the highest value （P〈0.01）. Additionally, no statistically significant differences were found in the acetate to propionate ratios among treatments groups （P〉0.05）, even the treatments stearic acid and a-linolenic acid were numerically higher than the others. The inclusion of 3% long-chain unsaturated fatty acids differing in the degree of unsaturation brought out a significant quadratic regression relation between the total VFA concentration and the double bond number of fatty acid. In conclusion, the a-linolenic acid with 3 double bonds appeared better for improving rumen microbial fermentation and the total VFA concentration.

Microbial Community Profiles Related to Volatile Fatty Acids Production in Mesophilic and Thermophilic Fermentation of Waste Activated Sludge Pretreated by Enzymolysis

Mesophilic and thermophilic anaerobic fermentation performance of waste activated sludge(WAS)pretreated by enzymes catalysis associated with microbial community shifts were investigated.WAS disintegration was boosted considerably by enzymolysis with 8750 mg/L of soluble COD release within 180 min.Mesophilic anaerobic fermentation(MAF)produced nearly equal VFA accumulation with over 3200 mg COD/L compared with that of thermophilic fermentation(TAF).Bacterial community consortia showed great shifting differences in dynamics of main T⁃RFs between MAF and TAF.Moreover,MAF was conducive to form intermediate bacterial community evenness compared to TAF,which preserved a robust function of VFA production.The enzymes catalysis prompted bio⁃energy(electricity)recovery potential of WAS organics via anaerobic fermentation(MAF/TAF)with evaluating electricity conversion efficiency of 0.75-0.82 kW·h/kg VSS(3.9 times higher than control test).Finally,this study proposed some novel thinking on future WAS treatment/management towards energy recovery coupled with energy⁃sufficient wastewater treatment by co⁃locating WAS anaerobic fermentation,MFC plant with wastewater treatment plant(s).

BAIMUXIFURANIC ACID,A NEW SESQUITERPENE FROM THE VOLATILE OIL OF AQUILARIA SINENSIS(LOUR.)GILG.

A new sesquiterpenoid,named baimuxifuranic acid,has been isolated from the volatile oil of Aquilaria sinensis(Lour.)Gilg.belonging to the family Thymelaceae by silica gel column chromatography.Based on spectral analysis its structure was deduced as(1).Reduction of baimuxifuranic acid by LiAlH_4 gave a

Effects of Ultrasonic and Acid Pretreatment on Food Waste Disintegration and Volatile Fatty Acid Production

This study aims at investigating the effects of ultrasonic and acid pretreatment on food waste( FW)disintegration and volatile fatty acid( VFA) production. Single-factor experiments are carried out to obtain optimal conditions of individual ultrasonic and acid pretreatment,and response surface method( RSM) is applied to optimize the conditions of the combination of ultrasonic and acid( UA) pretreatment. Results show that the optimal acid,ultrasonic and UA pretreatments conditions are individual pH 2,individual ultrasonic energy density of 1. 0 W / mL and the combination of ultrasonic energy density1. 11 W / mL and pH 1. 43,respectively. Correspondingly,the maximum disintegration degrees( DD) of 46. 90%,57. 38% and68. 83%are obtained by acid,ultrasonic and UA pretreatments,respectively. After optimizing pretreatment conditions,batch experiments are operated to produce VFA from raw and pretreated FW under anaerobic fermentation process. Both the maximum VFA production( 976. 17 mg COD / gV S) and VFA / SCOD( 72. 89%) are obtained with ultrasonic pretreatment, followed by UA pretreatment, non-pretreatment and acid pretreatment,respectively. This observation demonstrates that a higher acidity on acid and UA pretreatments inhibits the generation of VFA. Results suggest that ultrasonic pretreatment is preferable to promote the disintegration degree of FW and VFA production.

Processing Effect on the Physicochemical and Volatile Fatty Acid Profile of African Breadfruit (Treculia africana) Seed Oil

African breadfruit seeds were subjected to three processing methods—parboiling, cooking and toasting, and the raw was used as control. The purpose of this research was to extract the oil from the seed and to determine the effect of processing on the oil for physicochemical properties and volatile fatty acid profile. Physicochemical properties showed that the colour of the oil varied from golden yellow to brownish yellow with specific gravity varying between 0.802 g/cm3 and 0.813 g/cm3. Percentage yield of oil was 6.14% for raw extract, 6.62% for parboiled extract, 7.56% for toasted extract, and 5.01% for cooked extract. Acid, peroxide and saponification value for oil extracted from the raw seed varied with the processed samples value. The Volatile Fatty Acid (VFA), also known as Short Chain Fatty Acid (SCFA) found inherent in varying concentration, were formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, isocarproic, hexanoic and heptanoic acid. Overall results prove that heat results in increases in the VFA concentration of the processed oil.

Linkages of volatile fatty acids and polyhexamethylene guanidine stress during sludge fermentation:Metagenomic insights of microbial metabolic traits and adaptation

The massive use of polyhexamethylene guanidine(PHMG),as a typical bactericidal agent,raised environmental concerns to the public.This work comprehensively revealed the hormesis effects of PHMG occurred in waste activated sludge(WAS)on the generation of volatile fatty acids(VFAs)during anaerobic fermentation.The low level of PHMG(100 mg/g TSS)significantly promoted the VFAs generation(1283 mg COD/L,compared with 337 mg COD/L in the control)via synchronously facilitating the solubilization,hydrolysis,and acidification steps but inhibiting methanogenesis.Metagenomic analysis showed that the functional anaerobe(i.e.,Bacteroides,Macellibacteroide and Parabacteroide)and corresponding genetic expressions responsible for extracellular hydrolysis(i.e.,clp P),membrane transport(i.e.,ffh and gsp F),intracellular substrates metabolism(i.e.,ald and paa F)and VFAs biosynthesis(i.e.,ACACA and FASN)were enhanced in the optimal presence of PHMG.Moreover,the anaerobic species could respond and adapt to low PHMG stimuli via quorum sensing(i.e.,cqs A,rpf C and rpf G),and thus maintain the high microbial metabolic activities.However,they were unable to tolerate the toxicity of excessive PHMG,resulting in the extremely low VFAs production.This work enlightened the effects of emerging pollutants on WAS fermentation at the genetic levels,and provided guidance on the WAS treatment and resource recovery.

Evaluation of in vitro digestibility of Aspergillus oryzae fungal biomass grown on organic residue derived‑VFAs as a promising ruminant feed supplement

Background As demand for high quality animal feed continues to raise,it becomes increasingly important to mini-mize the environmental impact of feed production.An appealing sustainable approach to provide feed fractions is to use organic residues from agro-food industry.In this regard,volatile fatty acids(VFAs)such as acetic,propionic and butyric acids,derived from bioconversion of organic residues can be used as precursors for production of micro-bial protein with ruminant feed inclusion potential.This study aims to investigate the in vitro digestibility of the Asper-gillus oryzae edible fungal biomass cultivated on VFAs-derived from anaerobic digestion of residues.The produced fungal protein biomass,along with hay clover silage and rapeseed meal were subjected to various in vitro assays using two-stage Tilley and Terry(TT),gas,and bag methods to evaluate and compare its digestibility for application in ruminant feed.Results The produced fungal biomass contained a higher crude protein(CP)(41%–49%)and rather similar neutral detergent fiber(NDF)(41%–56%)compared to rapeseed meal.The rumen in vitro dry matter digestibility(IVDMD)of the fungal biomass in the TT method ranged from 82%to 88%(statistically similar to that of the gas method(72%to 85%)).The IVDMD of fungal biomass were up to 26%and 40%greater than that of hay clover silage and rapeseed meal,respectively.The type of substrate and bag method had pronounced effect on the fermentation products(ammonium-N(NH4+-N),total gas and VFAs).Fungal biomass digestion resulted in the highest release of NH4+-N(340–540 mg/L)and the ratio of acetate to propionate ratio(3.5)among subjected substrates.Conclusion The results indicate that gas method can be used as a reliable predictor for IVDMD as well as fermenta-tion products.Furthermore,the high IVDMD and fermentation product observed for Aspergillus oryzae fungal biomass digestion,suggest that the supplementation of fungal biomass will contribute to improving the rumen digestion by providing necessary nitrogen and energy to the ruminant and microbiota.

Releasing characteristics of phosphorus and other substances during thermal treatment of excess sludge

The releasing characteristics of phosphorus, nitrogen compounds, organics, and some metal cations during thermal treatment of excess sludge were investigated. It was found that during heating not only phosphorus, but also nitrogen compounds, organics, and some metal cations could be released in abundance. The maximum orthophosphate （ortho-P） release of about 90 mg/L in concentration was observed at 50℃ in 1 h. Except for volatile fatty acids （VFAs）, comparatively little total nitrogen （TN）, total organic carbon （TOC）, and metal cations were released at the same time. Such results might favor further process of phosphorus recovery. VFAs were considerably released only at 50℃. Acetic, butyric, and propionic acid were the most abundant components in turn and their releasing profiles exhibited good linear relationship with time （R2 = 0.9977, 0.9624, and 0.8908, respectively）. The concentrations of Mg^2＋ and K^＋ increased with time and temperature during thermal treatment, but Ca^2＋ decreased. The release of Mg^2＋ and K^＋ agreed well with TP release （R^2 = 0.9892 and 0.9476, respectively）. Temperature in the experimental range had very little impact on the linear relationships, especially of Mg^2＋. Moreover, the parameter of mixed liquor suspended solids （MLSS） was found to be an important factor for thermal sludge treatment as the released ortho-P and total phosphorus （TP） at 50℃ increased more than one-fold when MLSS was increased from 4000 to 8000 mg/L.

Transformation of organic matters in fresh leachate during anaerobic degradation under long hydraulic retention time

This study investigated the biodegradability of fresh leachate from a young municipal solid waste landfill at the inoculum to substrate ratios （V/V） of 10/100, 25/100, 50/100 and 100/100, as well as the transformation of organic matters in leachate under prolonged hydraulic retention time （HRT） of 50 d. Fresh leachate showed a good biodegradability, with chemical oxygen demand （COD） removal efficiency as high as 87%-92% and cumulative methane yield close to theoretical value （0.35 L CH4/g CODdeg）. Methane production and COD depletion presented biphasic characteristics associated with the successive utilization of two major intermediates, acetate and propionate, The biphasic degradation of fresh leachate was resulted from the different hydrolysis rates of diverse substrates and the changes in microorganism community structure. After 50 d, the effluents were dominated by high-MW organic compounds （MW 〉 10 kDa） at each inoculum ratio, which might be refractory compounds released from cell lyses.

Reduced inorganic sulfur in the sediments of the Yellow Sea and East China Sea

Cold diffusion methods are used to separate and quantify the three reduced inorganic sulfur species into acid volatile sulfide （AVS）, pyrite-S and element sulfur （ES） in the sediments of the Yellow and East China Seas. The results show that up to 25.02 pmol/g of AVS, 113.1 pmol/g of pyrite-S and 44.4 pmol/g of ES are observed in the sediments of the Yellow Sea and East China Sea. Pyrite-S is the predominant sulfide mineral in the sediments, while the concentration of AVS is quite low at most stations in the study area. The amounts and reactivity of organic matter are the primary limited factor for the sulfide formation, while an iron limitation and a sulfate limitation are not observed in the sediments of the Yellow Sea and East China Sea. The irregular profiles of the three reduced inorganic sulfur sediment composition and sedimentation rates. species also reflected the comprehensive influence of

Effects of sludge age on anaerobic acidification of waste activated sludge: Volatile fatty acids production and phosphorus release

Effects of sludge age on volatile fatty acids (VFAs) production and Phosphorus (P) release during anaerobic acidification of waste activated sludge (WAS) were investigated.Sequencing batch reactors (SBR) fed with simulating domestic sewage were applied to produce WAS of different sludge ages,and batch tests were used for anaerobic acidification.The maximum dissolved total organic carbon,release of PO_(4)^(3+)-P,and accumulation of acetate (C2),propionate (C3),butyrate (C4),and valerate (C5) decreased by 56.2%,55.8%,52.6%,43.7%,82.4%and 84.8%,respectively,as the sludge age of WAS increased from 5 to 40 days.Limited degradation of protein played a dominating role in decreasing DTOC and VFAs production.Moreover,the increase in molecular weight of organics and organic nitrogen content in the supernatant after acidification suggested that the refractory protein in WAS increased as sludge age extended.Although the production of C2,C3,C4,and C5 from WAS decreased as the sludge age increased,the proportions of C2 and C3 in VFAs increased,which might be due to the declined production of C5 from protein and the faded genus Dechlorobacter.Keeping sludge age of WAS at a relatively low level (<10 days) is more appropriate for anaerobic acidification of WAS as internal carbon sources and P resource.

Enhanced nitrogen removal upon the addition of volatile fatty acids from activated sludge by combining calcium peroxide and low-thermal pretreatments

This study investigated a combined low-thermal and CaO_(2)pretreatment to enhance the volatile fatty acid(VFA)production from waste activated sludge(WAS).The fermentative product was added to a sequencing batch reactor(SBR)as an external carbon source to enhance nitrogen removal.The results showed that the combined pretreatment improved WAS solubilization,releasing more biodegradable substrates,such as proteins and polysaccharides,from TB-EPS to LB-EPS and S-EPS.The maximum VFA production of 3529±188 mg COD/L was obtained in the combined pretreatment(0.2 g CaO_(2)/g VS+70℃for 60 min),which was 2.1 and 1.4-fold of that obtained from the sole low-thermal pretreatment and the control test,respectively.Consequently,when the fermentative liquid was added as an external denitrification carbon source,the effluent total nitrogen decreased to Class A of the discharge standard for pollutants in rural wastewater treatment plants in most areas of China.

Dietary pectic oligosaccharide supplementation improves rat reproductive performance via regulating intestinal volatile fatty acids during middle gestation

As a kind of green additive,pectic oligosaccharide(POS) may regulate some physiological functions of animals,such as gut health,antioxidant capacity,immunity and lipid metabolism.This study aimed to identify whether POS administration can improve maternal reproduction,and to determine the possible metabolism.A total of 48 pregnant Wistar rats randomly allotted into 2 groups,and each group was fed a diet supplemented with 0 or 800 mg/kg of POS.Pectic oligosaccharide administration increased rat born number(P <0.05),did not affect rat embryo number on d 7 of gestation,but increased rat fetus number on d 14 of gestation(P <0.05).On d 14 of gestation,POS treatment improved Lactobacillus and Bifidobacterium populations and volatile fatty acid concentrations of cecal digesta(P <0.05),hormone(progesterone and nitric oxide) and cytokine(interleukin 2) concentrations of serum(P <0.05),and antioxidant capacity of serum(increased total antioxidant capacity and decreased malondialdehyde) and placenta(increased total superoxide dismutase,decreased malondialdehyde)(P <0.05) in pregnant rats.These results suggest that POS administration improved rat reproduction via decreasing fetus loss in middle gestation.This was due to the increased volatile fatty acid concentrations in rat gut improving hormone and inflammatory-cytokine productions,and antioxidant capacity.

Impact of undissociated volatile fatty acids on acidogenesis in a two-phase anaerobic system

This study investigated the degradation and production of volatile fatty acids（VFAs）in the acidogenic phase reactor of a two-phase anaerobic system.20 mmol/L bromoethanesulfonic acid（BESA）was used to inhibit acidogenic methanogens（which were present in the acidogenic phase reactor）from degrading VFAs.The impact of undissociated volatile fatty acids（un VFAs）on＂net＂VFAs production in the acidogenic phase reactor was then evaluated,with the exclusion of concurrent VFAs degradation.＂Net＂VFAs production from glucose degradation was partially inhibited at high un VFAs concentrations,with 59%,37% and 60% reduction in production rates at 2190 mg chemical oxygen demand（COD）/L undissociated acetic acid（un HAc）,2130 mg COD/L undissociated propionic acid（un HPr）and 2280 mg COD/L undissociated n-butyric acid（un HBu）,respectively.The profile of VFAs produced further indicated that while an un VFA can primarily affect its own formation,there were also un VFAs that affected the formation of other VFAs.

A novel online analyzer for accurate and rapid measurement of volatile fatty acids in anaerobic wastewater treatment

Volatile fatty acids(VFAs), which are largely generated during the anaerobic acidification process, are considered to be reliable indicators of the stable process operation. However,the common methods for monitoring VFAs are offline, and they are typically manual requiring time-consuming, costly and complex instruments. This study aims to develop a novel online analyzer for automatic measuring VFAs, which was based on the 5-p H point titration, embedded with a proportional-integral-derivative(PID) feedback control system. The results show that it can achieve accurate and rapid monitoring of VFAs ranging between 0-400 mg/L(<9 min/sample) but simultaneously faces the problems of overtitration and interference of complex characteristics of wastewater. In order to improve its accuracy and stability, the effects of three general coefficients(K_(I),K_(P), and K_(D)) of PID on the titration were investigated, and the optimal values of K_(I), K_(P), and K_(D)were found to be 1.5, 1.0, and-1.0~0.5,respectively. Besides, the initial titration speed was set at 0.06 m L/min, equal to the minimum speed of the peristaltic pump, and the dichotomy approach was integrated into the PID feedback controller. Owing to the above improvements, the relative mean deviation and standard deviation of measuring VFAs in both synthetic and real wastewaters were mostly lower than 5.0% and 5.0 mg/L, proving the online analyzer is rapid, accurate and reliable.

Effects of Encapsulated Enzyme and Yeast Products on in Vitro Rumen Fermentation

Batch cultures of mixed rumen micro-organisms were conducted to evaluate the effects of encapsulated yeast(+EY)and encapsulated enzyme(+EE)using plant proteins(barley and oats grain)on rumen fermentation in vitro,investigate the abilities of encapsulated yeast and encapsulated enzyme to prevent rumen digestion in vitro.Treatments of the study were the control,+EY,+EE products(3.33 mg·mL^(-1) of the incubation medium),unencapsulated yeast(-EY)and enzyme(-EE)products(0.17 and 0.17μL·mL^(-1) of the incubation medium,respectively).+EY group increased dry matter disappearance(DMD,P<0.01)and the total volatile fatty acids(TVFA,P<0.01)at 3 h of the incubation compared with the control,regardless of encapsulation of yeast.Gas production(GP)of+EY group was higher(P=0.05,29.94 mL·mL^(-1) organic matter,OM)than that of the control(25.08 mL·g^(-1) OM)at 3 h of the incubation.Supplementation+EY increased DMD(P=0.04,0.394 vs 0.352,respectively)and acetic proportion(P=0.04,52.6 vs 49.8 mol•100 mL^(-1),respectively)at 6 h of the incubation and increased A:P ratio(P<0.01,3.11 and 2.86,respectively)at 24 h of the incubation,as compared to unencapsulation of yeast.Supplementation of enzyme had higher(P≤0.04)GP,DMD and TVFA at 3 and 6 h of the incubation compared with the control,regardless of encapsulation.Moreover,the addition of+EE produced greater GP at 6(P<0.01,92.35 vs 78.21 mL·g^(-1) OM,respectively),12(218.47 vs 159.18 mL·g^(-1) OM)and 24 h(380.97 vs 297.78 mL·g^(-1) OM,respectively)of the incubation,higher DMD(0.347 vs 0.313,respectively)at 3 h of the incubation as compared to-EE group.The study showed that the encapsulation might protect part of yeast and enzyme from releasing to the rumen throughout the digestion in vitro,resulting in higher or no difference of rumen fermentation parameters compared with unencapsulated groups at any incubation times.In comparison with-EY and-EE,the higher rumen fermentation parameters at the early incubation time were observed,which could be attributed to the higher concentration of yeast or enzyme.However,regardless of the encapsulation,the results indicated that both yeast and enzyme only improved the speed rather than the extent of rumen fermentation in vitro.

A Study on the Mechanism Regulating Acetate to Propionate Ratio in Rumen Fermentation by Dietary Carbohydrate Type

The research direction of our team is nutrition and physiology of ruminants, including dietary nutrition metabolism and rumen microorganisms. Previous research has shown that ruminal acetate-to-propionate ratio is related to diet utilization efficiency. At present, it is believed that the main factors affecting the ruminal acetate-to-propionate ratio are the degradation rate of the diet and the rumen microbial structure, but the main mechanism is unclear. This study found that the effect of ruminal acetate-to-propionate ratio was not affected by the concentration of the fermentation substrate, but was affected by the structure of the rumen microbiota. We believe that changes in the rumen microflora structure are the main mechanism for regulating the ruminal acetate-to-propionate ratio. This will help people to further understand the rumen physiology, thereby gradually improving feed conversion efficiency and reducing production costs. Abstract: In order to explore the mechanism by which diet regulates the acetate-to-propionate molar ratio (A: P ratio), we compared the effect on rumen fermentation parameters and the microbiome by altering the ratio of dietary concentrates to roughage ratio and calcium pyruvate infusion. The test animals were Laoshan dairy goats, and were fed continuously through an automatic feeder. The test groups were fed a base diet of low concentrates, and intraruminally infused with calcium pyruvate at two concentrations. The infusion concentrations were derived from the difference in the rate of carbohydrate degradation of the high and low concentrate diets, and they were artificially set such that the high concentration infusion group was infused with twice the concentration as the low concentration infusion group. The control groups were fed high concentrate (6:4) and low concentrate (3:7) diets, respectively. The following results were obtained by measuring rumen fermentation parameters and microbial composition: the rumen A: P ratio was significantly lower in the high-concentrate diet group than in the low concentrate diet group (P < 0.05). Infusion of low concentration calcium pyruvate had no significant effect on rumen A: P ratio (P > 0.05), while infusion of high concentration calcium pyruvate significantly increased the rumen A: P ratio (P < 0.05). Relative to goats fed the low concentrate diet, those fed the high concentrate diet had a greater abundance of microbes related to propionate production and a reduced abundance of microbes related to fiber degradation. Infusion of pyruvate had no significant effect on rumen microbial structure. The above results indicate that increasing the concentration of the fermentation substrate without affecting the composition of the microflora does not reduce the A: P ratio. Microbiological results showed that the A: P ratio was more closely related to the rumen microflora structure. Therefore, it is believed that rumen microflora structure is the main mechanism regulating A: P ratio in rumen fermentation.

Potassium ferrate pretreatment promotes short chain fatty acids yield and antibiotics reduction in acidogenic fermentation of sewage sludge

During the acidogenic fermentation converting waste activated sludge (WAS) into shortchain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (such as antibiotics) during acidogenic fermentation is unknown. In this study, potassium ferrate (KFeO) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with KFeOcan effectively increase the SCFA production during acidogenic fermentation and change the distribution of SCFA components.With the dosage of 0.2 g/g TS, the maximum SCFA yield was 4823 mg COD/L, which is 28.3times that of the control group;acetic acid accounts for more than 90% of the total SCFA. The higher dosage (0.5 g/g TS) can further increase the proportion of acetic acid, but inhibit the overall performance of SCFA production. Apart from the promotion of hydrolysis and acidogenesis, KFeOpretreatment can also simultaneously oxidizes and degrades part of the antibiotics in the sludge. When the dosage is 0.5 g/g TS, the degradation efficacy of antibiotics is the most significant, and the contents of ofloxacin, azithromycin, and tetracycline in the sludge are reduced by 69%, 42%, and 50%, respectively. In addition, KFeOpretreatment can also promote the release of antibiotics from sludge flocs, which is conducive to the simultaneous degradation of antibiotics in the subsequent biological treatment process.