Fermentative Acid Production Research Articles

Acetic Acid Fermentation of Soybean Molasses and Characterisation of the Produced Vinegar.

SUMMARYSoybean molasses is a by-product from the production of protein concentrate from soybean meal that predominantly contains sugars, with sucrose as the major component. In Brazil, soybean molasses is used for animal feed or it is discarded, although some industries use it to produce ethanol. This study aims to evaluate the parameters required for the acetic acid fermentation of soybean molasses, and characterise the resultant vinegar. To study the most suitable parameters for the acetic acid fermentation, vinegar was produced from the alcohol fermentation of soybean molasses through eight fermentation cycles: five for adaptation and three for production. The average acidity of the acetic acid fermentation product was 50.60 g/L, with an acetic acid fermentation yield, total yield of acetic acid in broth and productivity 65.01%, 92.76% and 0.033 g/(L·h), respectively. The vinegar produced from soybean molasses has an acidity of 5.07% (m/V), residual ethanol content 0.17% (m/V), sugars 7.86% (m/V), dry extract 14.67% (m/V), ash 2.27% (m/V) and a density of 1.023 g/cm3. The contents of total phenolics and isoflavones decreased after the alcohol and acetic acid fermentations. Moreover, the isoflavones profile of the fermented product comprised only three forms: daidzein, glycitin and genistin. According to our results, 3460 L of vinegar can be produced for every tonne of soy molasses, with an acetic acid concentration of 40 g/L, the minimum required by the legislation on vinegar production. Thus, these findings demonstrate that soy molasses represents a useful raw material for the production of vinegar.

Alteration of metabolic profiles in Lemna paucicostata culture and enhanced production of GABA and ferulic acid by ethephon treatment.

Lemna species have been used in the food, feed, and pharmaceutical industries, as they are inexpensive sources of proteins, starches, and fatty acids. In this study, we treated L. paucicostata with different concentrations (0.05, 0.1, 0.2, 0.5, or 1 mM) of ethephon. The total dry weight decreased in all ethephon-treated groups compared to the control group. We also investigated the alteration of metabolic profiles induced by ethephon treatment by using gas chromatography-mass spectrometry. This analysis identified 48 metabolites, and the relative levels of most of alcohols, amino acids, fatty acids, and phenols increased by the ethephon treatment, whereas levels of organic acids and sugars decreased. Among these, the highest production of γ-aminobutyric acid (GABA, 5.041 ± 1.373 mg/L) and ferulic acid (0.640 ± 0.071 mg/L) was observed in the 0.5 mM and the 0.2 mM ethephon treatment groups, respectively. These results could be useful for large-scale culture of L. paucicostata with enhanced GABA and ferulic acid content for utilization in the food, feed, cosmetic, and pharmaceutical industries.

Isolation, identification and characterization of soil bacteria for the production of ferulic acid through co-culture fermentation using banana stem waste

Exploitation of soil bacteria for production of ferulic acid (FA) is extensively performed since bacteria are the largest soil community that have the potential in producing degrading enzymes. This study aims to isolate, identify and characterize the most efficient soil bacteria for high FA yield via co-culture fermentation of banana stem waste (BSW). Bacteria were isolated and screened from acclimatized mixture of soil culture and BSW. ARB programme package and biolog system were employed for identification and characterization. The results reveal that four isolates closely related to Bacillus spp. and one Lysinibacillus sp. had greater potential to produce FA in very large amounts. Specifically, the maximum FA yield of 394.76 mg/kg was achieved using co-culture of Bacillus sp. MB2, Bacillus sp. WB8A and B. pumilus strain WB1A, which was 2.5-fold higher than FA produced by single culture. The profiles of substrate utilization exposed strong hydrolyzation of pectin in those three potential cultures, while one showed strong hydrolyzation of glucuronic acid. The ability to efficiently hydrolyze the components proves that the chosen co-cultures are good sources of hydrolytic enzymes. The results suggest that the co-culture has contributed cooperative actions among the cultures to synergistically breakdown the FA linkage in BSW to produce high FA yield.

Application of Michaelis–Menten in the kinetics of oil palm frond enzymatic hydrolysis for ferulic acid production

Ferulic acid (FA) production has become a frequent focus on today’s research due to its antioxidant properties. However, there has been little to none studies reported on the usage of mixed culture as inoculum in FA production. This study aims to determine the kinetics FA production in a mixed culture fermentation by applying the Michaelis–Menten kinetic model. In this study, mixed culture fermentation process using oil palm frond bagasse (OPFB) as substrate was applied for FA production improvement. Optimum condition was applied to study ferulic acid esterase (FAE) mechanism for kinetic modelling purposes. The kinetic model used was based on the Michaelis–Menten kinetic model. Runge–Kutta Fourth Order method was used to solve the kinetic model. Maximum FAE activity was achieved at the 28 h of fermentation process at 3.7 × 10−3 mU mL−1. This result proved that enzymatic hydrolysis occurred during fermentation process. Kinetic study was conducted with Michaelis–Menten kinetic model used as a reference kinetic equation. Three kinetic constants, Vmax, Km and Ks were determined as 3.725 × 10−3 g L−1 h−1, 28.231 g L−1 and 1.33 × 10−2 h−1 respectively using Runge–Kutta Fourth Order approach. The outcome of this study confirms that the kinetics of the process fit well with the Michaelis–Menten model. This also suggests that the usage of mixed culture has the potential to induce enzymatic hydrolysis hence improving FA production from OPFB during fermentation process.

Impact of feedstocks and downstream processing technologies on the economics of caproic acid production in fermentation by Megasphaera elsdenii T81

Caproic acid (CA) was produced by Megasphaera elsdenii T81 with Jerusalem artichoke tubers (JA) as a feedstock. More CA was produced under the medium with the acid hydrolysate of JA than the comparative medium with a carbon composition similar to that of JA. CA was produced up to 13.0 g/L and 0.52 g/L/h with extractive fermentation using a mixed solvent of alamine 336 in oleyl alcohol at 37 °C. The JA cost to produce 1 ton of CA is only 505 USD, which is much lower than that required for purchasing sucrose (860 USD) in CA production. As a result of the analysis performed using SuperPro Designer, including the cost of distillation to obtain pure CA, the estimated production cost for CA from dry JA is 1869 USD/ton CA at the production scale of 2000 ton/year, which is lower than the current market price for petroleum-derived CA (~2500 USD/ton).

Substrate Use Prioritization by a Coculture of Five Species of Gut Bacteria Fed Mixtures of Arabinoxylan, Xyloglucan, β-Glucan, and Pectin.

Dietary fiber provides growth substrates for bacterial species that belong to the colonic microbiota of humans. The microbiota degrades and ferments substrates, producing characteristic short-chain fatty acid profiles. Dietary fiber contains plant cell wall-associated polysaccharides (hemicelluloses and pectins) that are chemically diverse in composition and structure. Thus, depending on plant sources, dietary fiber daily presents the microbiota with mixtures of plant polysaccharides of various types and complexity. We studied the extent and preferential order in which mixtures of plant polysaccharides (arabinoxylan, xyloglucan, β-glucan, and pectin) were utilized by a coculture of five bacterial species (Bacteroides ovatus, Bifidobacterium longum subspecies longum, Megasphaera elsdenii, Ruminococcus gnavus, and Veillonella parvula). These species are members of the human gut microbiota and have the biochemical capacity, collectively, to degrade and ferment the polysaccharides and produce short-chain fatty acids (SCFAs). B. ovatus utilized glycans in the order β-glucan, pectin, xyloglucan, and arabinoxylan, whereas B. longum subsp. longum utilization was in the order arabinoxylan, arabinan, pectin, and β-glucan. Propionate, as a proportion of total SCFAs, was augmented when polysaccharide mixtures contained galactan, resulting in greater succinate production by B. ovatus and conversion of succinate to propionate by V. parvula Overall, we derived a synthetic ecological community that carries out SCFA production by the common pathways used by bacterial species for this purpose. Systems like this might be used to predict changes to the emergent properties of the gut ecosystem when diet is altered, with the aim of beneficially affecting human physiology.IMPORTANCE This study addresses the question as to how bacterial species, characteristic of the human gut microbiota, collectively utilize mixtures of plant polysaccharides such as are found in dietary fiber. Five bacterial species with the capacity to degrade polymers and/or produce acidic fermentation products detectable in human feces were used in the experiments. The bacteria showed preferential use of certain polysaccharides over others for growth, and this influenced their fermentation output qualitatively. These kinds of studies are essential in developing concepts of how the gut microbial community shares habitat resources, directly and indirectly, when presented with mixtures of polysaccharides that are found in human diets. The concepts are required in planning dietary interventions that might correct imbalances in the functioning of the human microbiota so as to support measures to reduce metabolic conditions such as obesity.

Dietary Supplementation With Citrus Extract Altered the Intestinal Microbiota and Microbial Metabolite Profiles and Enhanced the Mucosal Immune Homeostasis in Yellow-Feathered Broilers.

The present study aimed to investigate the effects of citrus extract (CE) on intestinal microbiota, microbial metabolite profiles, and the mucosal immune status in broilers. A total of 540 one-day-old yellow-feathered broilers were randomly allotted into three groups and fed a basal diet (control group), or a basal diet containing 10 mg/kg of zinc bacitracin (antibiotic group), or 10 mg/kg of CE (CE group). Each treatment consisted of six replicates, with 30 broilers per replicate. After 63-day feeding, two broilers per replicate were randomly selected and slaughtered, and their ileal and cecal digesta and ileal tissue were collected for microbial composition, microbial metabolites, and gene expression analysis. The results showed that CE significantly increased the abundance of Barnesiella and Blautia than did the antibiotic group (adjusted P < 0.05), whereas it decreased the abundance of Alistipes and Bacteroides (adjusted P < 0.05). Meanwhile, the CE group also increased the numbers of Bifidobacterium and Lactobacillus than did the control and antibiotic groups (P < 0.05), whereas it decreased the number of Escherichia coli (P < 0.05). For microbial metabolites, dietary supplementation with CE increased the concentrations of lactate, total short-chain fatty acids, acetate, and butyrate in the cecum than did the control and antibiotic groups (P < 0.05), whereas it decreased the concentrations of amino acid fermentation products (ammonia, amines, p-cresol, and indole) (P < 0.05). Additionally, supplementation with CE up-regulated (P < 0.05) the mRNA expression of intestinal barrier genes (ZO-1 and Claudin) in the ileum than did both the control and antibiotic groups. However, antibiotic treatment induced gut microbiota dysbiosis, altered the microbial metabolism, and disturbed the innate immune homeostasis. In summary, these results provide evidence that dietary supplementation with CE can improve the intestinal barrier function by changing microbial composition and metabolites, likely toward a host-friendly gut environment. This suggests that CE may possibly act as an efficient antibiotic alternative for yellow-feathered broiler production.

Efficient ferulic acid and xylo-oligosaccharides production by a novel multi-modular bifunctional xylanase/feruloyl esterase using agricultural residues as substrates

Liberating high value-added compounds ferulic acid (FA) and xylo-oligosaccharides (XOSs) from agricultural residues is a promising strategy for the utilization of lignocellulose. In this study, a bifunctional xylanase/feruloyl esterase from bacterial consortium EMSD5 was heterogeneously expressed in Escherichia coli. Depending on the inter-domain synergism of the recombinant enzyme rXyn10A/Fae1A, high yields of FA (2.78, 1.82, 1.15 and 7.31 mg/g substrate, respectively) were obtained from 20 mg in-soluble wheat arabinoxylan, de-starched wheat bran, ultrafine-grinding corn stover and steam-exploded corncob. Meanwhile, 3.210, 1.235, 1.215 and 0.823 mg xylose/XOSs were also released. For cost-saving enzyme production, we firstly constructed a recombinant E. coli, which could secrete the bifunctional xylanase/feruloyl esterase out of cells. When the recombinant E. coli was cultured in medium containing 200 mg de-starched wheat bran, 474 μg FA and 18.2 mg xylose/XOSs were also detected. Hence, rXyn10A/Fae1A and the recombinant strain showed great applied potential for FA and XOSs production.

Culture fermentation of Lactobacillus in traditional pickled gherkins: Microbial development, chemical, biogenic amine and metabolite analysis.

Fermented cucumber pickles are the lactic acid fermentation products formed through the influence of microorganisms present in the environment. This study investigated the impacts of starter cultures, namely, Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus paraplantarum, typically utilized for the fermentation of traditional pickled gherkins, on fermentation process. The chemical (pH, total acidity and salt) and microbiological (total mesophilic aerobic bacteria, lactic acid bacteria and yeast-mould) changes were observed against the control sample during fermentation process. Moreover, the amounts of biogenic amines (BAs) and metabolites formed as a consequence of fermentation were determined using HPLC. It was found that the chemical analyses provided similar results for all the samples. The amount of total mesophilic aerobic bacteria and yeast-mould colonies in pickle sample containing L. plantarum 49 strain appeared to reduce significantly. The amount of BAs was the lowest for the pickle samples where L. plantarum strains were added. The amount of BAs was below the toxic value that could affect human health. More BAs were synthesized as the fermentation period increased. Lactate was seen to exist in the samples when pyruvate was present, and acetoin was converted into 2.3-butanediol during the fermentation period. It was concluded that the pickle sample for which L. plantarum 49 strain was used displayed a better fermentation profile (i.e., metabolite and biogenic amines) than the remaining samples. Producing a more delicious and reliable product using such characteristics of L. plantarum strains in pickled gherkins is believed to significantly contribute to the food industry.

The &lt;i&gt;in vitro&lt;/i&gt; digestion of neutral detergent fibre and other ruminal fermentation parameters of some fibrous feedstuffs in Damascus goat (&lt;i&gt;Capra aegagrus hircus&lt;/i&gt;)

1. Allen M.S., 1997. Relationship between fermentation acid production in the rumen and the requirement for physically effective fiber. J. Dairy Sci. 80, 1447–1462, https://doi.org/10.3168/jds.S0.... CrossRef Google Scholar

Deep-Subsurface Pressure Stimulates Metabolic Plasticity in Shale-Colonizing Halanaerobium spp.

Bacterial Halanaerobium strains become the dominant persisting microbial community member in produced fluids across geographically distinct hydraulically fractured shales. Halanaerobium is believed to be inadvertently introduced into this environment during the drilling and fracturing process and must therefore tolerate large changes in pressure, temperature, and salinity. Here, we used a Halanaerobium strain isolated from a natural gas well in the Utica Point Pleasant formation to investigate metabolic and physiological responses to growth under high-pressure subsurface conditions. Laboratory incubations confirmed the ability of Halanaerobium congolense strain WG8 to grow under pressures representative of deep shale formations (21 to 48 MPa). Under these conditions, broad metabolic and physiological shifts were identified, including higher abundances of proteins associated with the production of extracellular polymeric substances. Confocal laser scanning microscopy indicated that extracellular polymeric substance (EPS) production was associated with greater cell aggregation when biomass was cultured at high pressure. Changes in Halanaerobium central carbon metabolism under the same conditions were inferred from nuclear magnetic resonance (NMR) and gas chromatography measurements, revealing large per-cell increases in production of ethanol, acetate, and propanol and cessation of hydrogen production. These metabolic shifts were associated with carbon flux through 1,2-propanediol in response to slower fluxes of carbon through stage 3 of glycolysis. Together, these results reveal the potential for bioclogging and corrosion (via organic acid fermentation products) associated with persistent Halanaerobium growth in deep, hydraulically fractured shale ecosystems, and offer new insights into cellular mechanisms that enable these strains to dominate deep-shale microbiomes.IMPORTANCE The hydraulic fracturing of deep-shale formations for hydrocarbon recovery accounts for approximately 60% of U.S. natural gas production. Microbial activity associated with this process is generally considered deleterious due to issues associated with sulfide production, microbially induced corrosion, and bioclogging in the subsurface. Here we demonstrate that a representative Halanaerobium species, frequently the dominant microbial taxon in hydraulically fractured shales, responds to pressures characteristic of the deep subsurface by shifting its metabolism to generate more corrosive organic acids and produce more polymeric substances that cause "clumping" of biomass. While the potential for increased corrosion of steel infrastructure and clogging of pores and fractures in the subsurface may significantly impact hydrocarbon recovery, these data also offer new insights for microbial control in these ecosystems.

Extracellular secretion of feruloyl esterase derived from Lactobacillus crispatus in Escherichia coli and its application for ferulic acid production

A feruloyl esterase producing strain was isolated and identified as Lactobacillus crispatus S524. Its putative feruloyl esterase was heterogeneously expressed in Escherichia coli BL21 (DE3). Interestingly, the feruloyl esterase (FaeLcr) could be secreted into the culture medium with a relative high purity of 201.7 mg/L. FaeLcr was purified from the cell-free culture supernatant and appeared as a single protein band with the molecular mass of 28 kDa by SDS-PAGE. The optimal temperature and pH were determined as 65 °C and 7.0, and it showed prominent thermo-stability and alkali-stability. Furthermore, the purified FarLcr could release a maximal amount of 199 µg ferulic acid from 0.2 g de-starched wheat bran. Meanwhile, when cultured this recombinant E. coli strain in medium supplemented with 2 g de-starched wheat bran, 1.86 mg ferulic acid was also detected. These results suggested that the recombinant strain has a great potential application in feruloyl esterase and ferulic acid production.

Novel xylanolytic triple domain enzyme targeted at feruloylated arabinoxylan degradation

A three catalytic domain multi-enzyme; a CE1 ferulic acid esterase, a GH62 α-l-arabinofuranosidase and a GH10 β-d-1,4-xylanase was identified in a metagenome obtained from wastewater treatment sludge. The capability of the CE1-GH62-GH10 multi-enzyme to degrade arabinoxylan was investigated to examine the hypothesis that CE1-GH62-GH10 would degrade arabinoxylan more efficiently than the corresponding equimolar mix of the individual enzymes.CE1-GH62-GH10 efficiently catalyzed the production of xylopyranose, xylobiose, xylotriose, arabinofuranose and ferulic acid (FA) when incubated with insoluble wheat arabinoxylan (WAX-I) (kcat = 20.8 ± 2.6 s−1). Surprisingly, in an equimolar mix of the individual enzymes a similar kcat towards WAX-I was observed (kcat = 17.3 ± 3.8 s−1). Similarly, when assayed on complex plant biomass the activity was comparable between CE1-GH62-GH10 and an equimolar mix of the individual enzymes. This suggests that from a hydrolytic point of view a CE1-GH62-GH10 multi-enzyme is not an advantage. Determination of the melting temperatures for CE1-GH62-GH10 (71.0 ± 0.05 °C) and CE1 (69.9 ± 0.02), GH62 (65.7 ± 0.06) and GH10 (71 ± 0.05 °C) indicates that CE1 and GH62 are less stable as single domain enzymes. This conclusion was corroborated by the findings that CE1 lost ˜50% activity within 2 h, while GH62 retained ˜50% activity after 24 h, whereas CE1-GH62-GH10 and GH10 retained ˜50% activity for 72 h.GH62-GH10, when appended to each other, displayed a higher specificity constant (kcat/Km = 0.3 s−1 mg−1 ml) than the individual GH10 (kcat/Km = 0.12 s−1 ± 0.02 mg−1 ml) indicating a synergistic action between the two. Surprisingly, CE1-GH62, displayed a 2-fold lower kcat towards WAX-I than GH62, which might be due to the presence of a putative carbohydrate binding module appended to CE1 at the N-terminal. Both CE1 and CE1-GH62 released insignificant amounts of FA from WAX-I, but FA was released from WAX-I when both CE1 and GH10 were present, which might be due to GH10 releasing soluble oligosaccharides that CE1 can utilize as substrate. CE1 also displayed activity towards solubilized 5-O-trans-feruloyl-α-l-Araf (kcat = 36.35 s−1). This suggests that CE1 preferably acts on soluble oligosaccharides.

Effects of Koji amazake and Its Lactic Acid Fermentation Product by Lactobacillus sakei UONUMA on Defecation Status in Healthy Volunteers with Relatively Low Stool Frequency

Effects of <i>Koji amazake</i> and Its Lactic Acid Fermentation Product by <i>Lactobacillus sakei</i> UONUMA on Defecation Status in Healthy Volunteers with Relatively Low Stool Frequency

Anaerobic nitrate reduction divergently governs population expansion of the enteropathogen Vibrio cholerae.

To survive and proliferate in the absence of oxygen, many enteric pathogens can undergo anaerobic respiration within the host by using nitrate (NO3-) as electron acceptor 1,2. In these bacteria, NO3- is typically reduced by a nitrate reductase to nitrite (NO2-), a toxic intermediate that is further reduced by a nitrite reductase3. However, Vibrio cholerae, the intestinal pathogen that causes cholera, lacks a nitrite reductase, leading to NO2- accumulation during nitrate reduction4. Thus, V. cholerae is thought to be unable to undergo NO3--dependent anaerobic respiration4. Here, we show that during hypoxic growth, NO3- reduction in V. cholerae divergently impacts bacterial fitness in a manner dependent on environmental pH. Remarkably, in alkaline conditions, V. cholerae can reduce NO3- to support population growth. Conversely, in acidic conditions, accumulation of NO2- from NO3- reduction simultaneously limits population expansion and preserves cell viability by lowering fermentative acid production. Interestingly, other bacterial species such as Salmonella typhimurium, enterohemorrhagic Escherichia coli (EHEC) and Citrobacter rodentium also reproduced this pH-dependent response suggesting that this mechanism might be conserved within enteric pathogens. Our findings explain how a bacterial pathogen can use a single redox reaction to divergently regulate population expansion depending on fluctuating environmental pH.

Optimization of Transesterification Reactions with CLEA-Immobilized Feruloyl Esterases from Thermothelomyces thermophila and Talaromyces wortmannii.

Feruloyl esterases (FAEs, E.C. 3.1.1.73) are biotechnologically important enzymes with several applications in ferulic acid production from biomass, but also in synthesis of hydroxycinnamic acid derivatives. The use of such biocatalysts in commercial processes can become feasible by their immobilization, providing the advantages of isolation and recycling. In this work, eight feruloyl esterases, immobilized in cross-linked enzyme aggregates (CLEAs) were tested in regard to their transesterification performance, towards the production of prenyl ferulate (PFA) and arabinose ferulate (AFA). After solvent screening, comparison with the activity of respective soluble enzymes, and operational stability tests, FAE125 was selected as the most promising biocatalyst. A central composite design revealed the optimum conditions for each transesterification product, in terms of water content, time, and substrate ratio for both products, and temperature and enzyme load additionally for prenyl ferulate. The optimum product yields obtained were 83.7% for PFA and 58.1% for AFA. FAE125 CLEAs are stable in the optimum conditions of transesterification reactions, maintaining 70% residual activity after five consecutive reactions. Overall, FAE125 CLEAs seem to be able to perform as a robust biocatalyst, offering satisfactory yields and stability, and thus showing significant potential for industrial applications.

Silage and haylage for horses

AbstractThis review covers current understanding on the use of wrapped forages such as silage and haylage as forage sources in equine nutrition. Silage (dry‐matter content &lt;500 g per kg) generally have higher concentration of lactic acid and other fermentation products and has a lower pH compared to haylage (dry‐matter content &gt;500–840 g per kg), as the lack of water in haylage restricts fermentation. The differences in biochemical and microbial composition in forage conserved as silage, haylage and hay have not been reported to influence digestion or hindgut function in horses differently. Studies on equine intake and preference of forages conserved as silage, haylage or hay are scarce and contradictory; both low voluntary intake and preference for silage have been reported. Studies on aerobic storage stability of opened bales are few, but are needed, as daily forage consumption is often low on horse farms, which may increase the risk of aerobic deterioration of forage in opened bales before they have been fed. A high hygienic quality of wrapped forages for horses is crucial: (a) as mould spores may cause chronic respiratory disorders; (b) as mycotoxins may cause intoxications, skin problems, gastrointestinal disorders and reproduction failures; (c) as presence of Clostridium botulinum and its toxin botulin may cause fatal disease; and (d) as other microbes (e.g., Listeria monocytogenes) may cause illness in the horse. Further research is needed especially for systems of assessment of hygienic quality of haylage, and how to prolong aerobic storage stability in opened bales.

A low-complexity metabolic network model for the respiratory and fermentative metabolism of Escherichia coli.

Over the last decades, predictive microbiology has made significant advances in the mathematical description of microbial spoiler and pathogen dynamics in or on food products. Recently, the focus of predictive microbiology has shifted from a (semi-)empirical population-level approach towards mechanistic models including information about the intracellular metabolism in order to increase model accuracy and genericness. However, incorporation of this subpopulation-level information increases model complexity and, consequently, the required run time to simulate microbial cell and population dynamics. In this paper, results of metabolic flux balance analyses (FBA) with a genome-scale model are used to calibrate a low-complexity linear model describing the microbial growth and metabolite secretion rates of Escherichia coli as a function of the nutrient and oxygen uptake rate. Hence, the required information about the cellular metabolism (i.e., biomass growth and secretion of cell products) is selected and included in the linear model without incorporating the complete intracellular reaction network. However, the applied FBAs are only representative for microbial dynamics under specific extracellular conditions, viz., a neutral medium without weak acids at a temperature of 37℃. Deviations from these reference conditions lead to metabolic shifts and adjustments of the cellular nutrient uptake or maintenance requirements. This metabolic dependency on extracellular conditions has been taken into account in our low-complex metabolic model. In this way, a novel approach is developed to take the synergistic effects of temperature, pH, and undissociated acids on the cell metabolism into account. Consequently, the developed model is deployable as a tool to describe, predict and control E. coli dynamics in and on food products under various combinations of environmental conditions. To emphasize this point,three specific scenarios are elaborated: (i) aerobic respiration without production of weak acid extracellular metabolites, (ii) anaerobic fermentation with secretion of mixed acid fermentation products into the food environment, and (iii) respiro-fermentative metabolic regimes in between the behaviors at aerobic and anaerobic conditions.

Sharpea and Kandleria are lactic acid producing rumen bacteria that do not change their fermentation products when co-cultured with a methanogen

Sharpea and Kandleria are associated with rumen samples from low-methane-emitting sheep. Four strains of each genus were studied in culture, and the genomes of nine strains were analysed, to understand the physiology of these bacteria. All eight cultures grew equally well with d-glucose, d-fructose, d-galactose, cellobiose, and sucrose supplementation. d-Lactate was the major end product, with small amounts of the mixed acid fermentation products formate, acetate and ethanol. Genes encoding the enzymes necessary for this fermentation pattern were found in the genomes of four strains of Sharpea and five of Kandleria. Strains of Sharpea produced traces of hydrogen gas in pure culture, but strains of Kandleria did not. This was consistent with finding that Sharpea, but not Kandleria, genomes contained genes coding for hydrogenases. It was speculated that, in co-culture with a methanogen, Sharpea and Kandleria might change their fermentation pattern from a predominately homolactic to a predominately mixed acid fermentation, which would result in a decrease in lactate production and an increase in formation of acetate and perhaps ethanol. However, Sharpea and Kandleria did not change their fermentation products when co-cultured with Methanobrevibacter olleyae, a methanogen that can use both hydrogen and formate, and lactate remained the major end product. The results of this study therefore support a hypothesis that explains the link between lower methane yields and larger populations of Sharpea and Kandleria in the rumens of sheep.

Catechol derived from aronia juice through lactic acid bacteria fermentation inhibits breast cancer stem cell formation via modulation Stat3/IL-6 signaling pathway.

Cancer stem cells (CSCs) as a subpopulation of cancer cells are drug-resistant and radiation-resistant cancer cells to be responsible for tumor progress, maintenance and recurrence of cancer, and metastasis. This study isolated and investigated a new cancer stem cell (CSC) inhibitor derived from lactic acid fermentation products using culture broth with 2% aronia juice. The anti-CSC activity of aronia-cultured broth was significantly higher than that of the control. Activity-guided fractionation and repeated chromatographic preparation led to the isolation of one compound. Using nuclear magnetic resonance and ESI mass spectrometry, we identified the isolated compound as catechol. In this study, we report that aronia-fermented catechol has a novel inhibitory effect on human breast CSCs. Catechol inhibited breast cancer cell proliferation and mammosphere formation in a dose-dependent manner. This compound reduced the CD44high /CD24low subpopulation, ALDH-expressing cell population and the self-renewal-related genes nanog, sox2, and oct4. Catechol preferentially reduced mRNA transcripts and protein levels of Stat3 and did not induce c-Myc degradation. These findings support the novel utilization of catechol for breast cancer therapy via the Stat3/IL-6 signaling pathway. Our results suggest that catechol can be used for breast cancer therapy and that Stat3 expression is a marker of CSCs. Catechol inhibited Stat3 signaling by reducing Stat3 expression and secreted IL-6, a CSC survival factor. These findings support the novel utilization of catechol for breast cancer therapy via Stat3/IL-6 signaling.