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Background: Butyric acid (BA) is a short-chain fatty acid (SCFA) with anti-inflammatory properties, which promotes intestinal barrier function. Medium-chain fatty acids (MCFA), including caproic acid (CA), promote TH1 and TH17 differentiation, thus supporting inflammation. Aim: Since most SCFAs are absorbed in the cecum and colon, the measurement of BA in peripheral blood could provide information on the health status of the intestinal ecosystem. Additionally, given the different immunomodulatory properties of BA and CA the evaluation of their serum concentration, as well as their ratio could be as a simple and rapid biomarker of disease activity and/or treatment efficacy in MS. Methods: We evaluated serum BA and CA concentrations, immune parameters, intestinal barrier integrity and the gut microbiota composition in patients with multiple sclerosis (MS) comparing result to those obtained in healthy controls. Results: In MS, the concentration of BA was reduced and that of CA was increased. Concurrently, the microbiota was depleted of BA producers while it was enriched in mucin-degrading, pro-inflammatory components. The reduced serum concentration of BA seen in MS patients correlated with alterations of the barrier permeability, as evidenced by the higher plasma concentrations of lipopolysaccharide and intestinal fatty acid-binding protein, and inflammation. Specifically, CA was positively associated with CD4+/IFNγ+ T lymphocytes, and the BA/CA ratio correlated positively with CD4+/CD25high/Foxp3+ and negatively with CD4+/IFNγ+ T lymphocytes. Conclusion: The gut microbiota dysbiosis found in MS is possibly associated with alterations of the SCFA/MCFA ratio and of the intestinal barrier; this could explain the chronic inflammation that characterizes this disease. SCFA and MCFA quantification could be a simple biomarker to evaluate the efficacy of therapeutic and rehabilitation procedures in MS. [ABSTRACT FROM AUTHOR]

• Co-digestion of sewage sludge and organic waste for VFA production was studied. • Acetic acid dominated in short-term operation in batch mode. • An increasing proportion of organic waste increased valeric and caproic acid. • Caproic acid dominated during long-term operation in semi-continuous mode. • VFA-rich liquid achieved higher denitrification rate than acetate and methanol. Volatile fatty acids (VFAs) are intermediates of anaerobic digestion with high value and wide range of usage. Co-digestion of sewage sludge and external organic waste (OW) for VFA production can help achieve both resource recovery and ensure sustainable and innovative waste management. In view of this, the effect of substrate proportions on VFA production from co-digestion of primary sewage sludge and OW is studied. Long-term operation in a semi-continuous reactor was performed to assess the resilience of such a system and the VFA-rich effluent was tested for its ability to be used as carbon source for denitrification. Co-digestion was initially carried out in batch reactors with OW proportion of 0%, 25%, 50%, 75%, 100% in terms of COD and scaled up in a semi-continuous reactor operation with 50% OW. In the short-term operation in the batch mode, acetic acid dominated, however, increasing OW fraction resulted in increased valeric and caproic acid production. Moreover, in the long-term semi-continuous operation, caproic acid dominated, accounting for ≈55% of VFAs. The VFA-rich effluent from the semi-continuous reactor achieved the highest denitrification rate as a carbon source when compared with acetic acid and methanol. The results demonstrate that co-fermentation can increase VFA yield and shift products from acetic acid to caproic acid in long-term operation and the VFAs can be used within wastewater treatment plants to close the loop. [ABSTRACT FROM AUTHOR]

Using different chromatographic methods, four new compounds were isolated from the aerial parts of Suaeda monoica (Chenopodiaceae) along with 2-hydroxy-1-naphthoic acid (SCM-3). The structures of the new compounds were established as 6′-hydroxy-10′-geranilanyl naphtha-1-oate (SMC-1), 4,4,8β,10β-Tetramethyl-9β-isobutanyl decalin-13-ol-13-O-β-D-xylopyranoside (SCM-2), 6′-(2-hydroxynaphthalen-3-yl) hexanoic acid (SCM-4) and 1′-(2-Methoxy-3-naphthyl)-4′-(2′'-methylbenzoyl)- n -butane (SMC-5) by IR, EIMS and NMR (1 & 2D) analyses. All compounds (50 μg/mL) were tested for cell proliferative potential on cultured human liver cell HepG2 cells by MTT assay. The results revealed a marked cell proliferative potential of all compounds (1.42–1.48 fold) as compared to untreated control. The results of molecular docking and binding with specific proteins such as PTEN (Phosphatase and Tensin homolog) and p53 also justify the cell proliferative potential of the isolated compounds. Glide program with Schrodinger suit 2018 was used to evaluate the binding between SMC compounds and proteins (PTEN and p53). The binding affinity of all compounds was in order of 104–105 M−1 towards both PTEN and p53. All the SMC compounds have been found to bind at the active site of PTEN, thereby may prevent the binding of phosphatidylinositiol 3,4,5-triphosphate (PI3P). In the locked position, PTEN would not be able to hydrolyze PI3P and hence the PI3P regulated signaling pathway remains active. Similarly, SMC molecules were found to interact with the amino acid residues (Ser99, Thr170, Gly199, and Asp224) which are critically involved in the formation of tetrameric p53. The blockage of p53 to attain its active conformation thus may prevent the recruitment of p53 on DNA and hence may promote cell proliferation. [ABSTRACT FROM AUTHOR]

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Opuntia ficus-indica can grow in arid and semi-arid environments characterized by low water and nutrients availability. These features make it a more sustainable alternative to the common energy crops for biorefinery purposes. This work focused on the potential benefits of anaerobic processes applied to this plant. Specifically, it considered i) the substrate preparation, demonstrating the effect of the apparent viscosity on the process; ii) the evaluation of biomethane, Volatile Fatty Acids (VFAs), and caproic acid production in semi-continuous mode at different hydraulic retention times; iii) the purification of the Fatty Acids-rich output through pressure-driven membrane filtration. The rheology analysis found that a 5 %w/w water dilution of the substrate is needed to lower the apparent viscosity to 173 cP, which is below the acceptable apparent viscosity level of 200 cP for a good bioreactor mixing. Keeping this condition, the semi-continuous trials with the best biomethane performance was at HRT of 20 days, with 210 mLCH 4 /gVS and 232 mLCH 4 /gCOD in of production and specific yield, respectively. The VFAs and caproic acid production reached their best at Hydraulic Retention Time 5, with 26 and 7.9 gCOD/L of VFAs and caproic acid, corresponding to specific yields of 79 and 30 % respectively. Pressure-driven filtration at 330 kDa allowed to obtain a permeate with a VFAs and caproic acid content of 96.72%w/w. Finally, the adsorption and desorption tests allowed to separate caproic acid from the permeate and to concentrate it from about 7.5 g COD /L to about 26 g COD /L. [Display omitted] • Opuntia Ficus Indica was valorized for multiple bioproducts and biofuels productions. • Caproic acid and methane were maximized at HRT 5 and 20 days, respectively. • The yields of VFAs and caproic acid were of 79 % and 30 % on COD base, respectively. • 300 kDa filtration allowed to obtain a medium of about 97 % of only VFAs. • Activated carbons led to a complete separation of caproic acid from the other VFAs. [ABSTRACT FROM AUTHOR]

[Display omitted] • E. limosum was able to survive in the open culture during a continuous process. • SCCA were produced from glycerol and further elongated to MCCA with lactate. • Presence of E. limosum in an open culture boosted chain elongation to valerate. • Caproiciproducens species were dominant in the caproate producing open culture. • Imaging flow cytometry with machine learning discriminated the Eubacterium cells. The objective was to investigate the impact of the bioaugmentation on chain elongation process using glycerol, lactate and lactose as substrates in an open culture fermentation. In the batch trials the highest selectivity for chain elongation product, i.e. caproate, was observed in trials inoculated with co-culture of Megasphaera elsdenii and Eubacterium limosum grown on glycerol (28.6%), and in non-bioaugmented open culture run on lactose + lactate (14.8%). The results showed that E. limosum , out of two bioaugmented strains, was able to survive in the open culture. A continuous open culture fermentation of glycerol led to caproate and 1,3-propanediol (1,3-PDO) formation, while lactate addition led to 1,3-PDO and short chain carboxylates production. Moving the process into batch mode triggered even-carbon chain elongation. Presence of E. limosum promoted odd-carbon chain elongation and valerate production. Imaging flow cytometry combined with machine learning enabled the discrimination of Eubacterium cells from other microbial strains during the process. [ABSTRACT FROM AUTHOR]

Palm oil mill effluent (POME) was dark fermented into biohydrogen for clean energy production with volatile fatty acids (VFAs) as a byproduct. The VFAs remaining 70% in hydrogenic POME offer potential substrate for conversion into valuable medium-chain fatty acids (MCFA), presenting an opportunity for resource recovery and environmental mitigation. This study investigated the influence of varying operating parameters on continuous MCFA production from biohydrogenic POME through a stirred tank reactor. Optimizing MCFA production necessitates a 5.4 g/L ethanol load supplemented with 2.6 g/L NaHCO 3 and 1.5 L-CO 2 /L/d while maintaining a pH of 6.5 and a temperature of 35 °C. Under optimized conditions, a maximum MCFA production of 2.2 g-COD/L was achieved, consisting primarily of 1.8 g-COD/L caproic acid, 0.2 g-COD/L heptanoic acid, and 0.2 g-COD/L caprylic acid, translating to a total MCFA yield of 0.5 g-COD/g-COD and MCFA selectivity of 51% with Caproiciproducens sp. (45%), Lactobacillus sp. (21%), and Clostridium sp. (14%) as predominant bacteria. Notably, CO 2 loading significantly enhances MCFA production, particularly caproic and heptanoic acids. Remarkably, the system maintained stable MCFA production for an impressive 220 days. The microbial community in the reactor effectively removed total solids, volatile solids, chemical oxygen demand (COD), suspended solids of 42%, 61%, 31%, and 95%, respectively. Key bacteria like Caproiciproducens sp., C. kluyveri , Clostridium sp., and Sporanaerobacter sp. possess most of the enzymes required for the reverse β-oxidation pathway, an energy-efficient pathway for MCFA generation. This study makes a significant contribution to the field of biowaste valorization, specifically focusing on anaerobic fermentation for bio-based chemical production. Despite challenges related to butyric acid accumulation and inhibition, these findings offer promising potential for scaling up the fermentation process. [Display omitted] • High MCFA production and solid reduction from biohydrogenic POME was achieved. • The addition of ethanol, NaHCO 3 , and CO 2 enhanced MCFA production. • Caproiciproducens sp. is a key bacterium in chain elongation. • Caproiciproducens, Lactobacillus, and Clostridium were dominant microbial species. • MCFA production of 2.2 g-COD/L and a solid reduction of 95% was achieved. [ABSTRACT FROM AUTHOR]

Abstract Background Medium chain carboxylic acids, such as caproic acid, are conventionally produced from food materials. Caproic acid can be produced through fermentation by the reverse β-oxidation of lactic acid, generated from low value lignocellulosic biomass. In situ extraction of caproic acid can be achieved by membrane electrolysis coupled to the fermentation process, allowing recovery by phase separation. Results Grass was fermented to lactic acid in a leach-bed-type reactor, which was then further converted to caproic acid in a secondary fermenter. The lactic acid concentration was 9.36 ± 0.95 g L−1 over a 33-day semi-continuous operation, and converted to caproic acid at pH 5.5–6.2, with a concentration of 4.09 ± 0.54 g L−1 during stable production. The caproic acid product stream was extracted in its anionic form, concentrated and converted to caproic acid by membrane electrolysis, resulting in a >70 wt% purity solution. In a parallel test exploring the upper limits of production rate through cell retention, we achieved the highest reported caproic acid production rate to date from a lignocellulosic biomass (grass, via a coupled process), at 0.99 ± 0.02 g L−1 h−1. The fermenting microbiome (mainly consisting of Clostridium IV and Lactobacillus) was capable of producing a maximum caproic acid concentration of 10.92 ± 0.62 g L−1 at pH 5.5, at the border of maximum solubility of protonated caproic acid. Conclusions Grass can be utilized as a substrate to produce caproic acid. The biological intermediary steps were enhanced by separating the steps to focus on the lactic acid intermediary. Notably, the pipeline was almost completely powered through electrical inputs, and thus could potentially be driven from sustainable energy without need for chemical input. Graphical abstract Microbial and electrochemical production of lactic acid, caproic acid and decane from grass.

Abstract Background n-Caproic acid (CA), as a medium-chain carboxylic acid, is a valuable chemical feedstock for various industrial applications. The fermentative production of CA from renewable carbon sources has attracted a lot of attentions. Lactate is a significant intermediate waste in the anaerobic breakdown of carbohydrates that comprise 18–70% of the chemical oxygen demand (COD) in municipal and some industrial wastewaters. Recently, researchers (including our own group) reported the CA production using lactate as electron donor with newly identified microbiome systems. However, within such processes, it was hard to determine whether the CA production was completed by a single strain or by the co-metabolism of different microorganisms. Results Here, we report the CA production using lactate as electron donor using the strain CPB6, which we isolated from a microbiome for CA production as described previously. Strain CPB6 is affiliated with Clostridium cluster IV of the family of Ruminococcaceae based on 16S rRNA gene sequence analysis. The strain prefers acidic initial pH condition (pH 5.0–6.5), and the temperature ranging from 30 to 40 °C for CA production. In a fed-batch fermentation with non-sterilized lactate-containing organic wastewater as feedstock, strain CPB6 produced 16.6 g/L CA (from 45.1 g/L lactate) with a maximum productivity of 5.29 g/L/day. Enzyme assays with crude cell extract showed that CPB6 can metabolize acetate and butyryl-CoA to produce n-butyric acid, and acetate/n-butyrate and caproyl-CoA to produce CA, respectively. Conclusion This study demonstrated that high concentration of CA production can be obtained by a newly isolated pure culture CPB6. This strain can be employed as a powerful workhorse for high-efficient CA recovery from lactate-containing waste streams. Our preliminary investigation suggested that the CA production from lactate in strain CPB6 might be via the chain elongation pathway of the reverse β-oxidation; the detailed mechanism, however, warrants further investigation using various molecular microbiology techniques.

Efficient waste management is necessary to transition towards a more sustainable society. An emerging trend is to use mixed culture biotechnology to produce chemicals from organic waste. Insights into the metabolic interactions between community members and their growth characterization are needed to mediate knowledge-driven bioprocess development and optimization. Here, a granular sludge bioprocess for the production of caproic acid through sugar-based chain elongation metabolism was established. Lactic acid and chain-elongating bacteria were identified as the two main functional guilds in the granular community. The growth features of the main community representatives (isolate Limosilactobacillus musocae G03 for lactic acid bacteria and type strain Caproiciproducens lactatifermentans for chain-elongating bacteria) were characterized. The measured growth rates of lactic acid bacteria (0.051 ± 0.005 h -1 ) were two times higher than those of chain-elongating bacteria (0.026 ± 0.004 h -1 ), while the biomass yields of lactic acid bacteria (0.120 ± 0.005 g biomass/g glucose) were two times lower than that of chain-elongating bacteria (0.239 ± 0.007 g biomass/g glucose). This points towards differential growth strategies, with lactic acid bacteria resembling that of a r-strategist and chain-elongating bacteria resembling that of a K-strategist. Furthermore, the half-saturation constant of glucose for L. mucosae was determined to be 0.35 ± 0.05 g/L of glucose. A linear trend of caproic acid inhibition on the growth of L. mucosae was observed, and the growth inhibitory caproic acid concentration was predicted to be 13.6 ± 0.5 g/L, which is the highest reported so far. The pre-adjustment of L. mucosae to 4 g/L of caproic acid did not improve the overall resistance to it, but did restore the growth rates at low caproic acid concentrations (1-4 g/L) to the baseline values (i.e., growth rate at 0 g/L of caproic acid). High resistance to caproic acid enables lactic acid bacteria to persist and thrive in the systems intended for caproic acid production. Here, insights into the growth of two main functional guilds of sugar-based chain elongation systems are provided which allows for a better understanding of their interactions and promotes future bioprocess design and optimization., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Ulčar, Regueira, Podojsteršek, Boon and Ganigué.)

An anaerobic, Gram-positive, rod-shaped, motile and spore-forming bacterium, designated strain ZCY20-5 T , was isolated from pit clay of Chinese strong-aroma type Baijiu (Chinese liquor). Phylogenetic analyses based on 16S rRNA gene and genome sequences showed that strain ZCY20-5 T belonged to the genus Caproicibacterium , family Oscillospiracheae , but it showed low similarity to the type species Caproicibacterium amylolyticum LBM18003 T (98.00 %) and Caproicibacterium lactatifermentans LBM19010 T (95.67 %). In anaerobic yeast extract medium, growth was observed at 20-45 °C (optimum, 35-40 °C), at pH 4.0-9.0 (optimum, pH 6.5-7.0) and with 0.0-2.0 % NaCl (w/v). The predominant fatty acids were C 16 : 0 , C 14 : 0 , C 13 3-OH and C 16 3-OH, and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, three phospholipids of unknown structure containing glucosamine and two unidentified phospholipids. Strain ZCY20-5 T exhibited an 81.32 % pairwise average nucleotide identity value, a 78.98 % average amino acid identity value and a 22.30 % digital DNA-DNA hybridization value compared to its closest relative C. amylolyticum LBM18003 T . Based on morphological, physiological, biochemical, chemotaxonomic, genotypic and phylogenetic results, strain ZCY20-5 T represents a novel species of Caproicibacterium , and the type strain is ZCY20-5 T (=MCCC 1A19399 T =KCTC 25590 T ).

Short-chain fatty acids (SCFAs) are the product of the anaerobic intestinal bacterial fermentation of dietary fiber and resistant starch. An abnormal intestinal microbiota may cause a reduction in the production of SCFAs, which stimulate the development of intestinal epithelial cells, nourish enterocytes, influence their maturation and proper differentiation, reduce the pH, and are an additional source of energy for the host. There have been reports of the special role of SCFAs in the regulation of glucose and lipid metabolism during pregnancy. Aim: The aim of the study was to analyze the correlation of SCFAs with lipid and hepatic metabolism during pregnancy in relation to the body weight of pregnant women. Material and methods: This study was conducted in pregnant women divided into two groups: Obese (OW—overweight and obese women; n = 48) and lean (CG—control group; n = 48) individuals. The biochemical plasma parameters of lipid metabolism (TG, CH, LDL, HDL), inflammation (CRP), and liver function (ALT, AST, GGT) were determined in all of the subjects. SCFA analysis was performed in the stool samples to measure acetic acid (C 2:0), propionic acid (C 3:0), isobutyric acid (C 4:0 i), butyric acid (C 4:0 n), isovaleric acid (C 5:0 i) valeric acid (C 5:0 n), isocaproic acid (C 6:0 i), caproic acid (C 6:0 n), and heptanoic acid (C 7:0). Results: Statistically significant differences in the concentrations of C 3:0 and C 6:0 n were found between women in the OW group compared to the CG group. The other SCFAs tested did not differ significantly depending on BMI. The C 2:0, C 3:0, and C 4:0 n ratios showed differences in both OW and CG groups. In the OW group, no relationship was observed between the concentrations of the SCFAs tested and CRP, ALT, AST. A surprising positive relationship between C 5:0 n and all fractions of the tested lipids and branched C 5:0 with CHL, HDL, and LDL was demonstrated. In the OW group, HDL showed a positive correlation with C 3:0. However, lower GGT concentrations were accompanied by higher C 4:0 and C 5:0 values, and this tendency was statistically significant. Conclusions: The results of our research show that some SCFAs are associated with hepatic lipid metabolism and CRP concentrations, which may vary with gestational weight. Obesity in pregnancy reduces the amount of SCFAs in the stool, and a decrease in the level of butyrate reduces liver function.

The channels of formation and transformation of bifunctional (C5, C6) and monofunctional acids (C1, C5, C6) and their anhydrides during the liquid-phase oxidation of cyclohexane are reviewed. Adipic acid and adipic anhydride are predominantly formed by the radical-chain oxidation of 2-hydroxycyclohexanone. Destructive transformations of 1-hydroxycyclohexyloxyl and cyclohexyloxyl (at a low conversion of cyclohexane) radicals, which are formed by the homolytic decomposition of 1-hydroperoxy-1-hydroxy- or 1-hydroxy-1-alkylperoxy-, and hydroperoxycyclohexane, respectively, afford 6-hydroxyhexanoic and caproic acids. 6-Oxohexanoic acid can be formed by the decomposition of 2-hydroperoxycyclohexanone via the nonradical and radical routes, as well as by the oxidation of 2-hydroxycyclohexanone with peroxide compounds. Valeric and 5-hydroxypentanoic acids are predominantly resulted from the destructive transformations of the 2-oxocyclohexyloxyl radical. The shortening of carbon chain is explained by decarboxylation, decarbonylation, and elimination of formic acid. The ring closure of 5-hydroxypentanoic acid to 8-valerolactone prevents its further oxidation. The schemes for the formation of 5-oxopentanoic and glutaric acids by the oxidation of 6-oxohexanoic acid at the C(5)-H bonds were proposed. The transacylation of the initially formed anhydrides with carboxylic acids leads to mixed anhydrides, and their alcoholysis by cyclohexanol affords all cyclohexyl esters of mono- and dicarboxylic acids. [ABSTRACT FROM AUTHOR]

The factors that affect the pervaporation‐assisted esterification of caproic acid and isobutanol have been investigated in a batch reactor and compared with two different pervaporation reactors, in situ and ex situ reactors, with different configurations. The operating process parameters of the pervaporation modules can be adjusted to optimize the performance, which improves the conversion of reactants and reduces the operating costs. The performances of the reactors have been extensively studied and the membrane selectivity has been investigated in terms of the flux of individual reaction species. The mass transfer limitation of both pervaporation reactors was studied and suitably eliminated. In addition, the performance of the pervaporation reactors was investigated by evaluating the ratio of water removal rate to the water production rate. [ABSTRACT FROM AUTHOR]

The influence of medium‐chain glycerides on performance and gastrointestinal well‐being in weaning piglets was assessed. First, caproic (C6), caprylic (C8) and capric (C10) acid activity against Escherichia coli was screened in vitro. Pig flora of the whole small intestine was used as inoculum. Seven in vitro incubations were done in duplicate at pH = 3 and 5: C10 (15 mM), C8 (12 mM), C6 (15, 12, 10 mM), a non‐incubated‐negative control and incubated negative control. Culture suspensions were plated on E. coli‐selective agar. Controls showed bacterial growth. C6 and C8 showed no growth at both pH‐values, where C10 showed growth at pH = 5. Secondly, an in vivo study was done with 80 weaned piglets over 42 days, housed in pens of eight animals (five pens/treatment), fed a basal diet containing broken rice/soya bean meal/fish meal and supplemented with C6 and C8 in medium‐chain glyceride form (MCT6/8, 0.175%) or antibiotic growth promoter (AGP, 0.020%) (Kasetsart University, Thailand) serving as control. Feed intake, daily gain and feed‐to‐gain ratio did not differ between MCT6/8 and AGP. Per replicate, two random selected piglets were challenged intravenously with E. coli‐lipopolysaccharide (LPS) or saline solution (S) at Days 21 and 28. All challenged animals were sacrificed; blood and digestive tract samples (jejunum/ileum) were collected at Day 35. LPS challenge consistently reduced villus height and crypt depth for MCT6/8 and AGP. However, LPS‐challenged piglets supplemented with MCT6/8 restored villus height, where AGP did not. MCT6/8 piglets had higher serum IgA, more jejunal IgA‐positive plasma cells and goblet cells than AGP. At the ileal level, results were similar, though less pronounced. The present study offers new insight in the benefits of MCT6/8 over AGP in the post‐weaning period. There is in vitro anti‐microbial action of C6 and C8 on E. coli. In vivo, MCT6/8 also has protective effects in the small intestine that may result in growth promotion. [ABSTRACT FROM AUTHOR]

Winery wastewaters are acidic effluents with high content of organic matter and nutrients. Different initial values of chemical oxygen demand (COD), ranging from 4 to 50 g L−1, were tested in batch assays to evaluate the fermentative hydrogen production followed by a methane production step. The influence of adding a typical nutrient solution for hydrogen production was investigated. Nutrients include N-NH4, Mg, Fe, Co, Mn, I, Ni, and Zn. The best hydrogen production potential was obtained at a COD of 50 g L−1 without nutrient addition. This condition produced 528 mL H2 L−1. At a COD ≥ 35 g L−1, tests with only WW had a hydrogen potential 1.6 to 1.9 times higher than did tests where nutrients were added. The use of added nutrients reduced the hydrogen production by producing additional reduced acids, such as propionate and valerate. In a second stage, biomethane potential was evaluated using the effluent of a selected condition from hydrogen production tests. The methane production reached values of 207 ± 2.2 mL CH4 g−1 COD at 10 g COD L−1. The COD affected the specific methane production. The results of this study demonstrated the potential of winery effluents as a substrate for sequential hydrogen and methane production to increase the energy recovery from this effluent, with a maximum energetic yield and productivity of 7.15 kJ gCOD−1 and 11.51 kJ d−1. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The first attempt to produce caproic acid by M. hexanoica with s-HF/MBRs. • Caproic acid of 10.08 g L−1 was produced with the fastest productivity of 0.69 g L−1 h−1. • The s-HF/MBRs showing potentials on caproic acid production by co-culture process. Abstract In this study, a coculture bioprocess was developed with Clostridium strains producing butyric acid and Megasphaera hexanoica producing caproic acid from the butyric acid. The two bacterial strains were each cultivated in two submerged hollow-fiber membrane bioreactors (s-HF/MBRs), separately. Each fermentation broth was filtered through the membrane modules, and the filtered broth was either interchanged on another reactor or obtained sequentially through. Using s-HF/MBRs, the caproic acid concentration increased to 10.08 g L−1, with the fastest productivity of 0.69 g L−1 h−1, which higher than that previously reported. [ABSTRACT FROM AUTHOR]

Short-chain fatty acids (SCFAs) mediate the transmission of signals between the microbiome and the immune system and are responsible for maintaining balance in the anti-inflammatory reaction. Pregnancy stages alter the gut microbiota community structure, which also synthesizes SCFAs. The study involved 90 pregnant women, divided into two groups: 48 overweight/obese pregnant women (OW) and 42 pregnant women with normal BMI (CG). The blood samples for glucose, insulin, and HBA1c were analyzed as well as stool samples for SCFA isolation (C2:0; C3:0; C4:0i; C4:0n; C5:0i; C5:0n; C6:0i; C6:0n) using gas chromatography. The SCFA profile in the analyzed groups differed significantly. A significant positive correlation between C2:0, C3:0, C4:0n and anthropometric measurements, and between C2:0, C3:0, C4:0n, and C5:0n and parameters of carbohydrate metabolism was found. SCFA levels fluctuate during pregnancy and the course of pregnancy and participate in the change in carbohydrate metabolism as well. The influence of C2:0 during pregnancy on anthropometric parameters was visible in both groups (normal weight and obese). Butyrate and propionate regulate glucose metabolism by stimulating the process of intestinal gluconeogenesis. The level of propionic acid decreases with the course of pregnancy, while its increase is characteristic of obese women, which is associated with many metabolic adaptations. Propionic and linear caproic acid levels can be an important critical point in maintaining lower anthropometric parameters during pregnancy.

[Display omitted] • Food waste fermentation without inoculum under different pH was investigated. • Hydrolysis and acidogenesis processes were promoted with the increase of pH. • Caproic acid was produced at pH 6 through lactate-based chain elongation. • Functional microbial communities were orientationally enriched during fermentation. Caproic acid (CA) production from food waste (FW) is a promising way for waste recycling, while the fermentation processes need further exploration. In this study, FW acidogenic fermentation under different pH (uncontrolled, 4, 5, 6) using indigenous microbiota was investigated. Result showed that substrate hydrolysis, carbohydrate degradation and acidogenesis increased with the increase of pH. Although various microbial communities were observed in FW, lactic acid bacteria (Lactobacillus and Limosilactobacillus) were enriched at pH lower than 6, resulting in lactic acid accumulation. CA (88.24 mM) was produced at pH 6 accounting for 31.23% of the total product carbon. The enriched lactic acid bacteria were directionally replaced by chain elongators (Caproicibacter , Clostridium_sensu_stricto , unclassified_Ruminococcaceae) at pH 6, and carbohydrates in FW were firstly transformed into lactic acid, then to butyrate and CA through lactate-based chain elongation processes. This work provided a novel CA fermentation pathway and further enriched the FW valorization. [ABSTRACT FROM AUTHOR]

• Flow cytometry enables real-time and near-future bioprocess performance assessment. • Chain elongation community was translated into unique cytometric fingerprints. • Based on cytometric fingerprints, several community types could be identified. • Each community type reflects a specific reactor performance and community composition. • Machine learning algorithms predict production rates of key fermentation products. As part of the circular bio-economy paradigm shift, waste management and valorisation practices have moved away from sanitation and towards the production of added-value compounds. Recently, the development of mixed culture bioprocess for the conversion of waste(water) to platform chemicals, such as medium chain carboxylic acids, has attracted significant interest. Often, the microbiology of these novel bioprocesses is less diverse and more prone to disturbances, which can lead to process failure. This issue can be tackled by implementing an advanced monitoring strategy based on the microbiology of the process. In this study, flow cytometry was used to monitor the microbiology of lactic acid chain elongation for the production of caproic acid, and assess its performance both qualitatively and quantitatively. Two continuous stirred tank reactors for chain elongation were monitored flow cytometrically for over 336 days. Through community typing, four specific community types could be identified and correlated to both a specific functionality and genotypic diversity. Additionally, the machine-learning algorithms trained in this study demonstrated the ability to predict production rates of, amongst others, caproic acid with high accuracy in the present (R² > 0.87) and intermediate accuracy in the near future (R² > 0.63). The identification of specific community types and the development of predictive algorithms form the basis of advanced bioprocess monitoring based on flow cytometry, and have the potential to improve bioprocess control and optimization, leading to better product quality and yields. [Display omitted] [ABSTRACT FROM AUTHOR]

This experiment was conducted to determine effect of different extender on recovery and storage of epididymal ram spermatozoa. Testes were obtained from eight mature rams which were slaughtered at four different occasions, a pair in each session. Caudal epididymis was isolated and divided to four equal parts. Spermatozoa recovery from each part of the caudal epididymis was performed by milk (M), Tris (T), Tris plus caproic acid (T-C) and sodium citrate (S) extenders. Spermatozoa in each extender were divided into four parts and then the amount of 0 (E0), 5 (E5), 10 (E10) and 15% (E15) egg yolk were added. Samples were chilled to 4 °C and stored for 7 days. The evaluation of sperm motility, viability, membrane integrity and acrosome integrity were performed daily. The results showed that there was interaction between egg yolk and storage time and also egg yolk and extender on sperm motility (p < 0.05). Sperm motility was highest at 15 % egg yolk (25.6 %) on 7 d (p < 0.05). Sperm motility was higher in ME15 (57.8 %) and T-CE15 (62.3 %) than TE15 (53.4 %) and SE15 (41.9 %; p < 0.05). There was interaction among egg yolk, extender and storage time on acrosome integrity, membrane integrity and sperm viability (p < 0.05). On 7 d, there were no differences among ME15, T-CE15 and TE15 on sperm viability and membrane integrity. Acrosome integrity was higher in T-CE15 (75.25 %) than ME15 (62.5 %) on 7 d (p < 0.05). Therefore, Tris caproic extender was superior to other extender for recovery and storage of ram epididymal spermatozoa.

Abstract Background The trend in chemical insecticide development has focused on improving the efficacy against mosquitoes while reducing the environmental impact. Lethal lures apply an “attract-and-kill” strategy that draws the insect to the killing agent rather than bringing the killing agent to the insect. Methods In this study, the mosquito oviposition pheromone was extracted from the eggs of Aedes aegypti (L.) and further investigated with a combination of pheromone and granular temephos as a lethal lure. Results The compound caproic acid attracted significantly more egg-laying mosquitos at 1 ppm (660.83 ± 91.61) than the control (343.83 ± 56.24), which consisted of solvent only (Oviposition Activity Index: 0.316). Further investigation of the combination of caproic acid with granular temephos as a lethal lure attracted significantly more gravid female Ae. aegypti to oviposit their eggs than the temephos treated water and control. Conclusions This indicated the ability of caproic acid in acting as an attractant and counters the repellency effect of temephos. Additionally, the presence of temephos in the lethal lure also restricted the hatching of the eggs and killed any larvae that hatched.

Caproic acid is a precursor substance for the synthesis of ethyl caproate, the main flavor substance of nongxiangxing baijiu liquor. In this study, Clostridium butyricum GD1-1, a strain with high caproic acid concentration (3.86 g/l), was isolated from the storage pit mud of nongxiangxing baijiu for sequencing and analysis. The strain's genome was 3,840,048 bp in length with 4,050 open reading frames. In addition, virulence factor annotation analysis showed C. butyricum GD1-1 to be safe at the genetic level. However, the annotation results using the Kyoto Encyclopedia of Genes and Genomes Automatic Annotation Server predicted a deficiency in the strain's synthesis of alanine, methionine, and biotin. These results were confirmed by essential nutrient factor validation experiments. Furthermore, the optimized medium conditions for caproic acid concentration by strain GD1-1 were (g/l): glucose 30, NaCl 5, yeast extract 10, peptone 10, beef paste 10, sodium acetate 11, L-cysteine 0.6, biotin 0.004, starch 2, and 2.0% ethanol. The optimized fermentation conditions for caproic acid production by C. butyricum GD1-1 on a single-factor basis were: 5% inoculum volume, 35°C, pH 7, and 90% loading volume. Under optimal conditions, the caproic acid concentration of strain GD1-1 reached 5.42 g/l, which was 1.40 times higher than the initial concentration. C. butyricum GD1-1 could be further used in caproic acid production, NXXB pit mud strengthening and maintenance, and artificial pit mud preparation.

Abstract: Baijiu is a Chinese traditional distilled liquor with an annual yield over 13.12 million tons. Strong flavor baijiu (SFB) also called Luzhou‐flavor liquor, takes account for > 70% of the total baijiu produced. SFB is produced by an open solid fermentation process with a complex microbial ecosystem. Clostridium is one of the most important microorganisms for the formation of the main flavor compounds of SFB, such as ethyl caproate. In this paper, we review current research progress on the Clostridium in the SFB ecosystem, focusing on the species diversity, physiological and metabolic features along with interspecies interactions. Systems biology approaches for the study of Clostridium from SFB ecosystems were discussed and explored. Furthermore, current applications of Clostridium in SFB production were discussed. Practical Application: Strong flavor baijiu (SFB) accounts for more than 70% of total yield of Chinese baijiu, which exists for hundreds of years. Clostridium is common in SFB ecosystem and identified to be one of main contributors of flavor compounds in SFB. Study on the Clostridium from SFB ecosystem is not only helpful for the understanding of flavor compounds formation mechanism, but also the improvement of SFB quality. This study focuses on the current researches on the Clostridium species in SFB ecosystem, including the species diversity, physiological and metabolic features, and applications. [ABSTRACT FROM AUTHOR]

The caproic acid-producing bacterial consortium (CAPBC) J30, isolated from Chinese Luzhou-flavored liquor distillery's pit mud, produces caproic acid as a metabolite. Constructed a 16S rDNA gene clone library and analyzed amplified ribosomal DNA restriction analysis, Clostridium genus was found predominating in CAPBC J30 and C. kluyveri was the chief contributor to its caproic acid-producing ability Then based on the Daqu extraction medium, effects of different carbon sources, nitrogen sources and growth factors on the caproic acid-producing ability were investigated, among which six key factors were chosen and optimized by Taguchi design. The estimated optimal medium was the Daqu extraction medium added 10 g⋅-1 sodium acetate, ethanol 15 ml⋅-1, liquor tailing 15 ml⋅-1, urea 3g⋅1-1, yellow mud extraction 1 ml⋅-1, and (NH4)2S04 0.5 g⋅1-1. After cultivated in this optimized medium for 15 days at 37°C, the caproic acid yield was up to 5024.11 mg⋅-1. This optimal medium will help to produce high caproic acid of CAPBC J30 to circumvent bottlenecks encountered in the high effective and adaptable ingredients in the field of Chinses Luzhou-dwortd liquor manufacture. [ABSTRACT FROM AUTHOR]

Volatile fatty acids (VFAs) production is attracting interest as a sustainable approach to maximize resource recovery from organic wastes. This study explored the interlink between long-term system resilience of VFA production from primary sludge (PS) and external organic waste (OW) without pH control and the microbial community dynamics as well as the effect of substrate variability. The study elucidated the practicality of using VFA-rich effluent as a carbon source for wastewater denitrification. A 15 L bench-scale semi-continuous reactor was operated for 315 days with a feed of 70% v/v PS and 30% v/v OW and scaled up to a 2 m3 pilot-scale continuous reactor operated for 264 days. In the bench-scale study, the system was resilient with VFA production of up to 24,700 ± 400 mg COD/L and a yield of 506 ± 25 mg COD/g VS fed. The VFA composition was dominated by caproic acid up to 62% w/w. In the pilot-scale reactor, substrate variability influenced VFA production with a concentration of up to 21,500 ± 500 mg COD/L. The system was shown to be economically viable. The microbial community was dominated by Lachnospiraceae , Streptococcaceae and Comamonadaceae. The relative abundance of Lachnospiraceae gave a strong positive statistical correlation with caproic acid concentrations. The VFA-rich effluent exhibited a higher specific denitrification rate than methanol and acetate. Moreover, a continuous denitrification experiment with real nitrified wastewater resulted in a high nitrate removal efficiency with a maximum of 98%. The study demonstrates the production of bio-based products from organic wastes as alternatives to fossil-based products. [Display omitted] • Long-term VFA production from waste without pH control is feasible and resilient. • VFA composed mainly of caproic acid with a percentage of up to 62%. • VFA-rich liquid is proven to be suitable for denitrification even in the long-term. • Upscaling to a 2 m3 reactor shows the system's robustness and economic viability. • Lachnospiraceae dominated and positively correlated with caproic acid and total VFA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Caproic acid adsorbed on dolomite surface by chemical adsorption and hydrogen bond. • Caproic acid interacted with O(surf) using Ca2+ as medium to form a stable structure. • Ca2+ promoted fatty acid surface adsorption and enhanced flotation of dolomite. • Mg2+ did not bond with O(surf) and affect caproic acid adsorption on dolomite surface. Ca2+ and Mg2+ are unavoidable ions in the flotation pulp of phosphate ore, but its influence mechanism on flotation of dolomite is unclear. In this study, the adsorption of caproic acid on dolomite (1 0 4) surface in the absence and presence of Ca2+ and Mg2+ was investigated by density functional theory (DFT) calculation. The results show that the caproic acid could stably adsorb on the surface of dolomite by chemical adsorption and hydrogen bond. Ca2+ could be adsorbed on dolomite surface by bonding with O(surf), meanwhile the O(surf) experienced a significant relaxation. The caproic acid could interact with O(surf) using Ca2+ as the medium to form a more stable structure, both O of caproic acid and O(surf) could form σ bond and a weak π bond with Ca2+, respectively. The zeta potential and contact angle measurements further showed Ca2+ could promote the adsorption of the fatty acid on the surface of dolomite and increase the surface hydrophobicity to enhance the flotation effect. Mg2+ did not bond with O(surf), and not affect the adsorption of the fatty acid on dolomite surface and the flotation effect. [ABSTRACT FROM AUTHOR]