Short-chain Organic Acids Research Articles

Characteristics and Application of Rhodopseudomonas palustris as a Microbial Cell Factory.

Rhodopseudomonas palustris, a purple nonsulfur bacterium, is a bacterium with the properties of extraordinary metabolic versatility, carbon source diversity and metabolite diversity. Due to its biodetoxification and biodegradation properties, R. palustris has been traditionally applied in wastewater treatment and bioremediation. R. palustris is rich in various metabolites, contributing to its application in agriculture, aquaculture and livestock breeding as additives. In recent years, R. palustris has been engineered as a microbial cell factory to produce valuable chemicals, especially photofermentation of hydrogen. The outstanding property of R. palustris as a microbial cell factory is its ability to use a diversity of carbon sources. R. palustris is capable of CO2 fixation, contributing to photoautotrophic conversion of CO2 into valuable chemicals. R. palustris can assimilate short-chain organic acids and crude glycerol from industrial and agricultural wastewater. Lignocellulosic biomass hydrolysates can also be degraded by R. palustris. Utilization of these feedstocks can reduce the industry cost and is beneficial for environment. Applications of R. palustris for biopolymers and their building blocks production, and biofuels production are discussed. Afterward, some novel applications in microbial fuel cells, microbial electrosynthesis and photocatalytic synthesis are summarized. The challenges of the application of R. palustris are analyzed, and possible solutions are suggested.

Dynamics of Bioactive Compounds during Spontaneous Fermentation of Paste Obtained from Capsicum ssp.-Stage towards a Product with Technological Application.

Six cultivars of chili (Cherry, Bulgarian Chilli, Cayenne, Fatalii, Habanero, and Carolina Reaper) from two species (Capsicum annuum and Capsicum chinense) have been studied. Anaerobic, spontaneous fermentation of pure chili paste was conducted for 21 days at 20 °C. The unfermented (UCP) and fermented chili pastes (FCP) were both subjected to physicochemical and microbiological characterization consisting of capsaicinoid, ascorbic acid, short-chain organic acids, phenolic compounds, and simple sugars analysis. Cell viability for Lactic Acid Bacteria (LAB) and Leuconostoc was determined before and after fermentation. Results indicate that capsaicinoids are very stable compounds, as notable differences between unfermented and fermented samples could not be seen. Carolina Reaper and Fatalii cultivars were amongst the most pungent, whereas Cherry, Cayenne, and Bulgarian types were low to moderate in pungency. Average loss of total ascorbic acid was 19.01%. Total phenolic compounds ranged between 36.89–195.43 mg/100 g for the fresh fruits and 35.60–180.40 mg/100 g for the fermented product. Losses through fermentation were not significant (p < 0.05). Plate counts indicated low initial numbers for LAB in the fresh samples, values ranging between 50–3700 CFU/g (colony-forming units). After fermentation, day 21, concentration of LAB (3.8 × 106–6.2 × 108 CFU/g) was high in all samples. Fermented chilies paste with enhanced biochemical and bacterial properties might further be used in the technology of vegetable (brining) or meat (curing) products, processes that generally involve the fermenting activity of different microorganisms, especially (LAB). Thus, the purpose of this research was the investigation of biochemical and microbial transformations that naturally occur in fermented chilies with a future perspective towards technological applications in cured meat products.

A Retrospective Metabolomics Analysis of Gamma-Hydroxybutyrate in Humans: New Potential Markers and Changes in Metabolism Related to GHB Consumption.

GHB is an endogenous short-chain organic acid presumably also widely applied as a rape and knock out drug in cases of drug-facilitated crimes or sexual assaults (DFSA). Due to the endogenous nature of GHB and its fast metabolism in vivo, the detection window of exogenous GHB is however narrow, making it challenging to prove use of GHB in DFSA cases. Alternative markers of GHB intake have recently appeared though none has hitherto been validated for forensic use. UHPLC-HRMS based screening of blood samples for drugs of abuse is routinely performed in several forensic laboratories which leaves an enormous amount of unexploited data. Recently we devised a novel metabolomics approach to use archived data from such routine screenings for elucidating both direct metabolites from exogenous compounds, but potentially also regulation of endogenous metabolism and metabolites. In this paper we used UHPLC-HRMS data acquired over a 6-year period from whole blood analysis of 51 drivers driving under the influence of GHB as well as a matched control group. The data were analyzed using a metabolomics approach applying a range of advanced analytical methods such as OPLS-DA, LASSO, random forest, and Pearson correlation to examine the data in depth and demonstrate the feasibility and potential power of the approach. This was done by initially detecting a range of potential biomarkers of GHB consumption, some that previously have been found in controlled GHB studies, as well as several new potential markers not hitherto known. Furthermore, we investigate the impact of GHB intake on human metabolism. In aggregate, we demonstrate the feasibility to extract meaningful information from archived data here exemplified using GHB cases. Hereby we hope to pave the way for more general use of the principle to elucidate human metabolites of e.g. new legal or illegal drugs as well as for applications in more global and large scale metabolomics studies in the future.

In vitro susceptibility of swine pathogens to feed additives and active ingredients with potential as antibiotic replacements.

The rise in antibiotic resistance requires the reduction of antibiotic use in all sectors. In animal production, many commercial alternatives to antibiotics have been developed for incorporation into feeds, but a lack of evidence on their antibacterial activity limits confidence in their application. We aim to compare the antibacterial activity of feed additives and active ingredients to better understand their usefulness. The antibacterial activity of 34 active ingredients and feed additives, including medium- and short-chain organic acids and essential oils, was tested against pure cultures of five bacterial swine pathogens. Antibacterial activity was observed using an agar plug diffusion method and quantified via broth microdilution. A diverse range of antibacterial activities were observed. The highest inhibitory activity against Staphylococcus aureus and Streptococcus suis was exhibited by the C12 monoglyceride (0.49mgml-1 ). The monoglyceride of C12 was more effective than C12:0 against Strep. suis, but neither C12:0 nor its monoglyceride showed efficacy against the gram-negative micro-organisms tested. The most active against Escherichia coli were the C6:0 medium-chain organic acids and potassium diformate (1.95mgml-1 ). For Salmonella Typhimurium, potassium diformate, sodium diformate, and a blend of C8:0/C10:0 (each 1.96mgml-1 ), and for Actinobacillus pleuropneumoniae, eugenol (0.49mgml-1 ) showed the most promising activity. We identified broad-spectrum antibacterial activity, such as the C6:0 MCOA, and those with interesting narrow-spectrum activity, notably the killing of Strep. suis by C12 monoglyceride. We have identified additives that show the most promising bioactivity against specific pathogens. We broadly compare a large collection of feed additives and active ingredients for their antibacterial activity against a diverse panel of bacterial swine pathogens. This provides a solid base of evidence which can drive the development of feed supplementation strategies with the aim of reducing dependency on antibiotic use in swine production.

1H NMR and UPLC-HRMS-based metabolomic approach for evaluation of the grape maturity and maceration time of Touriga Nacional wines and their correlation with the chemical stability

Touriga Nacional is a well-adapted Portuguese grape variety in São Francisco River Valley (northeastern Brazil). Nevertheless, it has only been indicated to short-term consumption because of the lack of chemical stability, which is attributed to low grape acidity and incomplete phenolic maturity. Therefore, we used Ultra-Performance Liquid Chromatography coupled High-resolution Mass Spectrometry, Nuclear Magnetic Resonance and chemometrics (PCA and PLS-DA) to evaluate the grape maturity and maceration time on chemical composition of wines from two harvest seasons. Moreover, we investigated how these experimental factors could affect their chemical stability. Grapes maturity showed to be the main effect. Overall, phenolic acids and short-chain organic acids were found to be at higher levels in wines produced with unripe grapes from February and shorter maceration time (p < 0.05). Proanthocyanidins and other flavonoids were increased in wines macerated for longer time using overripe grapes harvested in July. Furthermore, stable wines were made from overripe grapes, which contained more galacturonic acid.

Synergistic Metabolism of Glucose and Formate Increases the Yield of Short-Chain Organic Acids in Escherichia coli.

Microbial cell factories using a single carbon source (e.g., sugars) have been used to produce a wide variety of chemicals. However, this process is often accompanied by stoichiometric constraints on carbons and redox cofactors. Here, a synthetic pathway was designed and constructed in Escherichia coli to synergistically use glucose and formate as mixed carbon sources. By optimizing this synthetic pathway via enzyme mining, protein engineering, and bioprocess approaches, the yield of pyruvate from glucose was enhanced to 94% of the theoretical glycolysis yield, reaching 1.88 mol/mol. Finally, the optimized synthetic pathway was integrated with a phosphite reductase-based NADH regeneration system in malate-producing E. coli, resulting in the conversion of glucose into l-malate with a high yield of up to 1.65 mol/mol. This synergistic carbon metabolism strategy can be used to establish carbon- and energy-efficient productive processes.

Selective Fermentation of Lactobacillus and Streptococcus In Vitro: Effects of Chinese Fermented Glutinous Rice on the Growth Promotion of Potential Probiotics

A functional Chinese fermented glutinous rice has been developed with the supplementation of Fu brick tea (CRW-FBT). In this study, we aimed to evaluate its effect on the growth of potential probiotic strains in the Lactobacillus, Streptococcus, and Weissella genus, compared with traditional Chinese fermented glutinous rice (CRW). The growth profiles of lactic acid bacteria were analyzed based on fermentations in vitro, and the optical densities were recorded at 600 nm during the whole fermentation. Growth curve, maximum OD600 nm, and growth rate were measured and compared among samples with different ratios of CRW-FBT and CRW addition. Through the multiple analysis of growth parameters, we found that all the tested strains obtained better growth results when CRW-FBT was supplemented to the media, compared with the CRW and basic media. The bacterial growth was promoted by exhibiting the shortened lag time, prolonged logarithmic phase and stationary phase, and increased growth rate and cell density, as well as the better performance after 24 h and 48 h fermentation. Besides, short-chain fatty acids and organic acids in CRW-FBT were founded. Our work demonstrated the positive effect of Fu brick tea supplemented in the CRW and illustrated its beneficial role in the food fermentation industry for the purpose of microorganism enrichment and the improvement of microbial metabolism.

Recovery of organic acids from pre-treated Kraft black liquor using ultrafiltration and liquid-liquid extraction

Kraft black liquor (BL) is a toxic residue from paper manufacture that can be revalorized to obtain high value-added products. In this study, different integrated processes, consisting of a pre-treatment (lignin recovery [LR] or partial wet oxidation [PWO]) followed by ultrafiltration (UF) and liquid–liquid extraction (LLE), have been evaluated in order to recover short-chain organic acids (OA) from BL.After the UF step, a partial purification of OA was observed. Thus, the COD fraction attributable to OA increase 26.0%, 36.6% and 11.3% for untreated BL, BL after lignin recovery (LRBL) and partially oxidised BL (WOBL), respectively.The final LLE step was optimised analysing different combinations of extractants (trioctylamine, trioctylphosphine oxide and tributylphosphate), diluents (n-hexane and heptane) and temperatures (25, 40 and 55 °C), concluding that the most suitable solvent was 30% trioctylamine in heptane (v/v) at 40 °C, in which 76% of the OA mass was recovered in LRBL, 72% in BL and 68% in WOBL.The pre-treatment of BL improved the final recovery yield of OAs, increasing from 24.7% to 28.1% and 29.4% through PWO and LR, respectively. Therefore, LR was considered the most suitable pre-treatment due to its lower operating cost, widespread use, and greater recovery of OA.

A Randomized Open Label Pilot Study of Clostridium Butyricum Miyairi 588 (CBM588) in Recipients of Allogeneic Hematopoietic Cell Transplantation

A Randomized Open Label Pilot Study of Clostridium Butyricum Miyairi 588 (CBM588) in Recipients of Allogeneic Hematopoietic Cell Transplantation

Development of an innovative technology for accelerated cooking of no yeast bread using ion-ozonized water

Natural baking starter made from common ingredients such as flour, water and sugar is considered healthy. Any starter obtained by spontaneous fermentation is always a symbiosis of lactic acid bacteria and yeast. Lactic acid bacteria and yeast get along well together and in the course of their life enrich bread with the most valuable compounds, including short-chain organic acids, dietary fiber, essential amino acids, vitamins, etc. On the basis of the obtained research results, a recipe and technological modes for preparing dough for no yeast bakery products from wheat flour of the first grade with the use of ion-ozonized water, whey and natural starter have been developed. The dough was prepared in a safe way under pressure in a kneading-beating ion-ozone cavitation unit. The recipe components (raw materials) of the dough were loaded into the kneading body of the unit, then the dough was replaced for 5 minutes at a kneading body rotation frequency of 5 s-1 in different rotation modes and times. Then the ion-ozone treatment was carried out using an excess pressure of 0.40 MPa (cavitation) and the dough was knocked down. The nutritional value, safety and shelf life of the developed no yeast bakery products with the addition of whey, starter and ion-ozonized water have been determined. It was found that in terms of organoleptic and physicochemical indicators, bread samples prepared from first grade wheat flour and ion-ozonized water without yeast and using whey are almost 2 times inferior to the quality of the control sample. As a result, it was found that churning for 3–5 minutes at a kneading body rotation frequency of 4–5 s-1 will be the optimal mode for obtaining a no yeast dough made from first grade flour on starter with the addition of whey and ion-ozonized water

N-induced root exudates mediate the rhizosphere fungal assembly and affect species coexistence

Root exudates play essential roles in shaping root-associated microbial communities in plant-soil systems. However, knowledge regarding the influence of root exudates on soil communities, particularly concerning their assembly processes and species coexistence patterns, remains limited. In this study, we performed a 20-month pot experiment using a nitrogen (N) addition gradient (0, 2.5, 5, 7.5, 10, and 15 g N m−2 yr−1), amplicon sequencing, and metabolomics to investigate the effect of short-term N addition on the assembly process and species coexistence of fungal communities, as well as their association with root exudates in the rhizosphere and bulk soils around Bothriochloa ischaemum. The results demonstrated that short-term N addition led to distinct differences in the diversity, composition, assembly process, and co-occurrence networks of fungal communities in the rhizosphere and bulk soils. The diversity of fungal communities in the rhizosphere soil increased with the rate of N input and peaked at N10 treatment; this could be correlated with the increased abundance in long-chain organic acids (LCOAs). However, above the threshold N rate of 10 g N m−2 yr−1, diversity decreased probably because of the high N-induced inhibitory effect on root exudates (i.e., LCOAs). N addition increased the relative abundance of Sordariomycetes in the rhizosphere and decreased the relative abundance of Mortierellomycetes in the bulk soil, while enhancing the abundance of pathotrophs in both bulk and rhizosphere soils. The rhizosphere fungal community was dominated by a stochastic process at a low N input (N0 and N2.5) and by deterministic processes at a high N input (N10 and N15), which is opposite to the trends in the bulk soil. These fungal assembly processes determine the coexistence of fungal species; deterministic processes lead to less interconnected networks in rhizosphere soils that harbor a more complex network than the bulk soil. Associations between the assembly process and species coexistence in the rhizosphere of B. ischaemum were closely related to the changes in root exudates, such as amino acids, short-chain organic acids, and phenols, which were stimulated by N addition. Collectively, our study emphasizes the key roles of root exudates in the establishment of fungal communities in the plant-soil system and furthers our understanding of plant-microbe interactions.

Anaerobic fermentation for the production of short chain organic acids: Product concentration, yield and productivity in batch experiments at high feed concentration

With the general aim of maximising product concentration, yield and productivity in the anaerobic fermentation (AF) of biomass to make short-chain organic acids (SCOAs) with low-cost and environmentally sustainable processes, this study investigates the effect of high substrate concentration on the batch digestion of model biomass at uncontrolled temperature. Five substrate concentrations, between 24.7 and 394.6 gCOD l−1 (the latter is the highest substrate concentration reported in the literature for these types of studies), were investigated in batch reactors with no pH control. The highest substrate concentration led to a maximum product concentration of 61.5 g l−1, composed mainly of lactic acid (85 wt%). The lowest substrate concentration produced mainly acetic acid (54 wt%). The pH was acidic in all cases but was higher for the most diluted feed (6.2). Similar yields at the end of the experiments, between 15.7% and 22.0% COD COD−1, were observed in all reactors. Over the length of the experiments, generally yields increased and productivities decreased, indicating the need of a compromise between yield and productivity. For the highest substrate concentration, a final productivity of 1.5 g l−1 d−1 was obtained. Experiments with pH adjustment in the range 4.0–6.0 were performed, and results generally showed an increase in product concentration, yield and productivity as the target pH increased, with the highest values of concentration, yield and productivity (163 g l−1, 56% COD COD−1 and 3.9 g l−1 d−1 respectively) obtained at pH 5.5.

Experimental investigation and mathematical modelling of batch and semi-continuous anaerobic digestion of cellulose at high concentrations and long residence times

In the context of the anaerobic digestion of slowly biodegradable substrates for energy and chemicals production, this study investigated the anaerobic digestion of cellulose without any chemical pre-treatments using open (undefined) mixed microbial cultures. The anaerobic conversion of cellulose was investigated in extended-length (run length in the range 518–734 days) batch and semi-continuous runs (residence time 20–80 days), at high cellulose concentration (20–40 g L−1), at temperatures of 25 and 35 °C. The maximum cellulose removal was 77% in batch (after 412 days) and 60% (at 80 days residence time) in semi-continuous experiments. In semi-continuous experiments, cellulose removal increased as the residence time increased however the cellulose removal rate showed a maximum (0.17 g L−1 day−1) at residence time 40–60 days. Both cellulose removal and removal rate decreased when cellulose concentration in the feed was increased from 20 to 40 g L−1. Liquid-phase products (ethanol and short chain organic acids) were only observed under transient conditions but not at the steady state of semi-continuous runs. Most of the observed results were well described by a mathematical model which included cellulose hydrolysis and growth on the produced glucose. The model provided insight into the physical phenomena behind the observed results.

Biogenic methane generation from Vietnamese coal after pretreatment with hydrogen peroxide

The application of coal as a methanogenic substrate is limited due to its recalcitrant nature, thus, requiring pretreatment for increasing bioavailability of coal. This paper describes the pretreatment of Vietnamese coal from the Red River Basin. The coal sample was treated with 3% (vol/vol) hydrogen peroxide, which resulted in 45.4% (weight %) solubilization of coal and release of various organics into the liquid phase. This dissolved fraction was analyzed for total dissolved organic carbon, Fourier transform infrared spectroscopy, high-performance size exclusion chromatography, and high-performance liquid chromatography. The detailed analytical investigations revealed the presence of aliphatics and aromatics hydrocarbons in the liquid phase. Short-chain organic acids, including oxalic, citric, malic, malonic, formic, and acetic acids were also observed. The dissolved fraction was subjected to methanogenesis. Methane generation achieved the peak at 218.5 μmol/g coal after 500 days of incubation. The effect of the pretreatment process on inorganic matter of the residual coal samples was also assessed using inductively coupled plasma mass spectrometry. The pretreatment caused a reduction in metal content of the residual coal sample. The findings of the paper can be prospected as a feasibility study of methane production from Vietnamese coal after its pretreatment using hydrogen peroxide.

Ingestion of High β-Glucan Barley Flour Enhances the Intestinal Immune System of Diet-Induced Obese Mice by Prebiotic Effects.

The prebiotic effect of high β-glucan barley (HGB) flour on the innate immune system of high-fat model mice was investigated. C57BL/6J male mice were fed a high-fat diet supplemented with HGB flour for 90 days. Secretory immunoglobulin A (sIgA) in the cecum and serum were analyzed by enzyme-linked immunosorbent assays (ELISA). Real-time PCR was used to determine mRNA expression levels of pro- and anti-inflammatory cytokines such as interleukin (IL)-10 and IL-6 in the ileum as well as the composition of the microbiota in the cecum. Concentrations of short-chain fatty acids (SCFAs) and organic acids were analyzed by GC/MS. Concentrations of sIgA in the cecum and serum were increased in the HGB group compared to the control. Gene expression levels of IL-10 and polymeric immunoglobulin receptor (pIgR) significantly increased in the HGB group. HGB intake increased the bacterial count of microbiota, such as Bifidobacterium and Lactobacillus. Concentrations of propionate and lactate in the cecum were increased in the HGB group, and a positive correlation was found between these organic acids and the IL-10 expression level. Our findings showed that HGB flour enhanced immune function such as IgA secretion and IL-10 expression, even when the immune system was deteriorated by a high-fat diet. Moreover, we found that HGB flour modulated the gut microbiota, which increased the concentration of SCFAs, thereby stimulating the immune system.

Long-chain phenols oxidation using a flow electrochemical reactor assembled with a TiO2-RuO2-IrO2 DSA electrode

The electrochemical degradation of long-chain phenols present in toxic residues from the cashew-nut processing industry was systematically investigated for the first time, using a flow electrochemical reactor assembled with a Ti/TiO2-RuO2-IrO2 DSA anode. After optimizing the current density (40 mA cm−2) and chloride concentration (0.028 mol L−1) in 0.5 mol L−1 Na2SO4 supporting electrolyte, it was achieved expressive total organic carbon (TOC) removal percentage for (un)saturated cardanol and cardol, either alone (85–92%) or in association/real industrial CNSL sample (82%), over 4 h of electrolysis. Evidently, the removal rate for the mixture changes (56–88% TOC removal) according to its starting concentration (0.005–0.100% residue), showing that the system performance can improve by increasing treatment time. Chromatography coupled to mass spectrometry (GC–MS) analysis showed that the first stage of the electrooxidation process was driven towards the formation of phenoxyl radicals, followed by the formation of polymeric dimers. These intermediates were continuously oxidized by different free and chemisorbed reactive species until obtaining short-chain organic acids, CO2 and H2O. The proposed system proved to be efficient, eco-friendly, and viable to treat industrial waste containing refractory phenolic compounds.

Humic acids trigger the weak acids stress response in maize seedlings

BackgroundPlants primed by humic acids showed physiological and molecular response against different abiotic stresses without the presence of stressor agents (salinity, drought, heavy metal toxicity). It is plausible that humic acids themselves can act as chemical priming substances in plants. We hypothesized that humic acids can trigger the weak acids stress response in cell plants acidifying the cytosol and thus eliciting the transduction signalling response cascade.MethodsThe dose–response curves of maize seedlings roots with different concentrations of humic, acetic and salicylic acids determined the most active and inhibitory concentration. These data were further used to evaluate changes on intracellular pH using BCECF-AM probe (2,7-bis(2-carboxyethyl)-5(and 6)-carboxyfluorescein, acetoxymethyl ester) and differential transcription level of genes related to weak stress response in plants by qPCR real time.ResultsHumic acids like short chain organic acids decrease the intracellular pH showed by the increased fluorescence of BCECF probe. The drop in cytosolic pH promoted by humic acids was not transient. We observed a high level of protein kinases related to cell energy-sensing and transcription factors associated to transduction of stress signalling.ConclusionThe humic acids can be considered as a chemical priming agent, since in the appropriate concentration they can induce the typical plant abiotic stress response of weak acids inducing plant acclimation and enhancing the abiotic stress tolerance.

PSIX-32 Assessment of Mucosa-associated Microbiota in the Colon and Rumen of Dairy Calves Fed High Plane of Milk and during Weaning Transition

Abstract The nature of weaning is considered as the most stressful period experienced by dairy calves and has been known to negatively affect calf growth and intake. The objectives of this study were to investigate the shift of rumen and colon mucosa-associated microbiota in dairy calves fed with a high plane of milk pre- and post-weaning, and whether such shifts are associated with rumen fermentation and growth performance. Six Holstein dairy bull calves were ruminally cannulated at the second week of life followed by weaning at the end of week 6. Ruminal and colon tissue samples were biopsied at the end of week 5, 7 and 12 to determine the bacterial community changes, and rumen content was collected at the same time to measure rumen fermentation parameters. QIIME2 was used to analyze microbial profiles and R studio software was used to determine the microbial changes and its relationship with phenotypic measures. Age-dependent profiles were observed for the colon mucosa associated microbiota but not for rumen mucosa associated microbiota, indicating that varied responses to weaning transition exists between colon and rumen mucosa associated microbiota. As calves aged, higher abundance of taxa such as Delftia (associated with hexadecanoic acid production) and lower abundance of Veillonella (associated with short-chain organic acids utilization) were detected in the colon mucosa. The rumen also displayed taxonomic changes with decreases in Pseudobutyrivibrio in older calves. In addition, we identified significantly positive correlations between Prevotella associated with rumen mucosa and average daily gain, Isovalerate and Isobutyrate, suggesting that this genus may promote rumen fermentation during weaning transition. Our findings suggest that weaning transition affects rumen and colon mucosa-associated bacteria, and some of the rumen mucosa-associated microbiota promote rumen fermentation during this period, which may have long-term effects on animal health and productivity.

Product Concentration, Yield and Productivity in Anaerobic Digestion to Produce Short Chain Organic Acids: A Critical Analysis of Literature Data

In order to make anaerobic digestion-based processes for short chain organic acid (SCOA) production attractive, the key performance variables, i.e., concentration, yield, and productivity of the produced SCOAs need to be maximised. This study analysed recent literature, looking for the effect of process operating parameters (feed concentration, pH, temperature, and residence time) on the performance variables. Data from 551 experiments were analysed. Mean values of the SCOA concentration, yield, and productivity were 10 g l−1, 32% (chemical oxygen demand (COD) COD−1), and 1.9 g l−1 day−1, respectively. Feed concentration and residence time had the most important effect. Higher feed concentration corresponded to higher product concentration and productivity, but to lower yield. The mean feed concentration was 109 gCOD l−1 and 19 gCOD l−1 in the experiments with the highest product concentrations and in the experiments with the highest yields, respectively. Shorter residence times corresponded to higher productivity. The mean HRT (hydraulic residence time) in the experiments with the highest productivities was 2.5 days. Sequencing batch reactors gave higher values of the performance variables (mean values 29 g l−1, 41% COD COD−1, and 12 g l−1 day−1 for product concentration, yield, and productivity, respectively) than processes without phase separation.

Root exudates mediate plant defense against foliar pathogens by recruiting beneficial microbes

Plants are capable of releasing specific root exudates to recruit beneficial rhizosphere microbes upon foliar pathogen invasion attack, including long-chain fatty acids, amino acids, short-chain organic acids and sugars. Although long-chain fatty acids and amino acids application have been linked to soil legacy effects that improve future plant performance in the presence of the pathogen, the precise mechanisms involved are to a large extent still unknown. Here, we conditioned soils with long-chain fatty acids and amino acids application (L + A) or short-chain organic acids and sugars (S + S) to examine the direct role of such exudates on soil microbiome structure and function. The L + A treatment recruited higher abundances of Proteobacteria which were further identified as members of the genera Sphingomonas, Pseudomonas, Roseiflexus, and Flavitalea. We then isolated the enriched bacterial strains from these groups, identifying ten Pseudomonas strains that were able to help host plant to resist foliar pathogen infection. Further investigation showed that the L + A treatment resulted in growth promotion of these Pseudomonas strains. Collectively, our data suggest that long-chain fatty acids and amino acids stimulated by foliar pathogen infection can recruit specific Pseudomonas populations that can help protect the host plant or future plant generations.