High Acetate Concentrations Research Articles

이산화탄소로부터 생물전기화학적 아세트산 생산을 위한 미생물 농화배양 및 군집 분석

Microbial electrosynthesis has recently been considered a potentially sustainable biotechnology for converting carbon dioxide (CO₂) into valuable biochemicals. In this study, bioelectrochemical acetate production from CO₂ was studied in an H-type two-chambered reactor system with an anaerobic microbial consortium. Metal-rich mud flat was used as the inoculum and incubated electrochemically for 90 days under a cathode potential of -1.1 V (vs. Ag/AgCl). Four consecutive batch cultivations resulted in a high acetate concentration and productivity of 93 m㏖/L and 7.35 m㏖/L/day, respectively. The maximal coulombic efficiency (rate of recovered acetate from supplied electrons) was estimated to be 64%. Cyclic voltammetry showed a characteristic reduction peak at -0.2~-0.4 V, implying reductive acetate generation on the cathode electrode. Furthermore, several electroactive acetate-producing microorganisms were identified based on denaturing- gradient-gel-electrophoresis (DGGE) and 16S rRNA sequence analyses. These results suggest that the mud flat can be used effectively as a microbial source for bioelectrochemical CO₂ conversion.

Influences of starter NDF level on growth performance and rumen development in lambs fed isocaloric and isonitrogenous diets.

Neutral detergent fiber (NDF), as the main component of structural carbohydrate in forage, is a vital factor impacting the performance of young ruminants. The objective of this study was to evaluate the effect of starter NDF level on the rumen fermentation and morphometrics of lambs fed isocaloric and isonitrogenous diets. One hundred Hu sheep lambs (18 days of age and 6.1 ± 0.1 kg body weight [BW]) were randomly assigned to one of the four starter diets differing in their NDF levels on a dry matter (DM) basis: 1) diet with 14% NDF (NDF14), 2) diet with 18% NDF (NDF18), 3) diet with 22% NDF (NDF22), and 4) diet with 26% NDF (NDF26). Lambs were fed milk replacer with designed starters from 21 to 60 d of age and then transitioned to the same starter feed until 90 d of age. Six lambs from each treatment (close to the average BW of the corresponding treatment) were selected and slaughtered at 90 d of age for measuring rumen fermentation, anatomical development, and morphometric characteristics. Lambs receiving NDF22 and NDF26 starter diets had greater (P < 0.05) intake of starter and total DM, and average daily gain during the overall period, thereby heavier (P < 0.05) final weights at 90 d of age compared with those fed NDF14 starter diet. At 90 d of age, lambs fed NDF22 and NDF26 starters had higher rumen pH, followed by lower propionate, higher acetate concentrations (P < 0.05), and a higher acetate-to-propionate ratio compared with those fed NDF14 and NDF18 starters (P < 0.05). No significant differences of the full and empty weight of reticulorumen were observed among treatments; however, the reticulorumen weight expressed as a percentage of the complex stomach weight was lower (P < 0.05) in lambs fed NDF22 and NDF26 starters compared with those fed NDF14 starter. Furthermore, NDF14 lambs had the thickest keratin layer and epithelium compared with those in the other treatments but showed the thinnest muscle layer (P < 0.05). These results suggest that increasing starter NDF levels can ameliorate the rumen fermentation environment and alleviate hyperkeratosis and plaque formation in the rumen epithelium. In summary, including 22% and 26% NDF in the pelleted starter can improve the performance of lambs.

Enhancement of syntrophic acetate oxidation pathway via single walled carbon nanotubes addition under high acetate concentration and thermophilic condition

The effect of single walled carbon nanotubes (SWCNT) on methane production under high acetate concentration and thermophilic condition was evaluated. An isotope labeling experiment verified that >85% of methane was generated from syntrophic acetate oxidation (SAO) at 50, 100 and 150 mM acetate and almost 100% at 200 mM. SWCNT addition had little effect on the methanogenesis pathway, whereas it accelerated methane production via decreasing lag phase times and increasing maximum methane production rates. Electrochemical impedance spectroscopy (EIS) results revealed the electrical resistivity of sludge in groups of SWCNT was distinctly smaller than CK groups, indicating higher sludge conductivity was achieved. Further, the results of communities described that Coprothermobacter and Thermacetogenium played the most important role in SAO under all conditions. Meanwhile, the enriched Thermacetogenium and direct interspecies electron transfer (DIET) pathway in SAO consortia contributed to the acceleration of methane production via SWCNT addition.

Acetate and Potassium Modulate the Stationary-Phase Activation of lrgAB in Streptococcus mutans.

Fluctuating environments force bacteria to constantly adapt and optimize the uptake of substrates to maintain cellular and nutritional homeostasis. Our recent findings revealed that LrgAB functions as a pyruvate uptake system in Streptococcus mutans, and its activity is modulated in response to glucose and oxygen levels. Here, we show that the composition of the growth medium dramatically influences the magnitude and pattern of lrgAB activation. Specifically, tryptone (T) medium does not provide a preferred environment for stationary phase lrgAB activation, which is independent of external pyruvate concentration. The addition of pyruvate to T medium can elicit PlrgA activation during exponential growth, enabling the cell to utilize external pyruvate for improvement of cell growth. Through comparison of the medium composition and a series of GFP quantification assays for measurement of PlrgA activation, we found that acetate and potassium (K+) play important roles in eliciting PlrgA activation at stationary phase. Of note, supplementation of pooled human saliva to T medium induced lrgAB expression at stationary phase and in response to pyruvate, suggesting that LrgAB is likely functional in the oral cavity. High concentrations of acetate inhibit cell growth, while high concentrations of K+ negatively regulate lrgAB activation. qPCR analysis also revealed that growth in T medium (acetate/K+ limited) significantly affects the expression of genes related to the catabolic pathways of pyruvate, including the Pta/AckA pathway (acetate metabolism). Lastly, stationary phase lrgAB expression is not activated when S. mutans is cultured in T medium, even in a strain that overexpresses lytST. Taken together, these data suggest that lrgAB activation and pyruvate uptake in S. mutans are connected to acetate metabolism and potassium uptake systems, important for cellular and energy homeostasis. They also suggest that these factors need to be implemented when planning metabolic experiments and analyzing data in S. mutans studies that may be sensitive to stationary growth phase.

Investigation of the Lactic Acid Bacteria in Kazak Cheese and Their Contributions to Cheese Fermentation.

Kazak cheese is a traditional dairy product fermented by lactic acid bacteria (LAB) in Xinjiang. To investigate the LAB in Kazak cheese and their contributions to cheese fermentation, four representative LAB, Streptococcus thermophilus B8, Lactobacillus helveticus B6, Weissella confusa B14, and Lactobacillus rhamnosus B10, were isolated from Kazak cheese and subsequently used to ferment cheeses, which were named StC, LhC, WcC, and LrC, respectively. The result showed that most of the physical and chemical indicators had no significant difference, except for moisture and fat. W. confusa B14 was beneficial to the production of amino acids, whereas S. thermophilus B8 promoted the formation of organic acids and contributed to formation ideal texture property. Furthermore, the four cheeses all possessed a strong fruity aroma, with brandy, sweet, herbaceous, pungent, and fatty aromas being the most prominent in WcC. This is because L. helveticus B6 produced a high concentration of hexanal, nonanal, octanal, 3-methylbutanoic acid, ethyl acetate, ethyl butanoate, isoamyl acetate, and ethyl hexanoate in LhC. Research on the fermentation mechanism of LAB in cheese will provide a theoretical basis for the quality control and industrial production of Kazak cheese.

Investigating the effect of apple pomac silage as fodder source on performance and residues of its toxins in milk and some rumen fermentation in Mahabadi lactation goats in early lactation period

The aim of this study was to evaluate effect of apple pomace silage as fodder source on performance and residues of its toxins in milk and some rumen fermentation in Mahabadi lactation goats in early lactation period. There was no significant difference within treatments apple pomace mixed silage had no effect on dairy goat’s average daily feed intake. There were no significant differences about pH changes between treatments. The protozoa population tended to decrease and ammonia nitrogen has increased significantly in different treatments (P≤0.05). According to the increase of volatile fatty acids production, the proportion of acetatenot differed even though that of Propionate and iso-butyrate increased but none significantly. The molar ratios of acetate and propionate and iso-butyratein the goats rumen containing apple pomace was differed in respect to the availability for fermentation by rumen microflora. In regard to this information, the inclusion of apple pomace silage in experimental goat’s diet was associated with a slight lower rumen pH, higher concentration of acetate and propionate and total volatile fatty acids in rumen. The potential value of byproducts in animal feeding and better dry matter and organic matter digestibilitydepends on their nutritive characteristics. But the livestock producers are responsible for ensuring that the animals and products that they market do not contain unacceptable chemical residues. Anyone intending to feed waste materials to ruminant animals such as cattle, sheep and goatsor to pigs must ensure that it is free of prohibited or restricted substances.

Ultramicrobacteria from Nitrate- and Radionuclide-Contaminated Groundwater

The goal of the present work was to investigate the physicochemical and radiochemical conditions and the microbial diversity in groundwater collected near the Lake Karachai (Russia), which was formerly used for the disposal of liquid radioactive waste, to isolate the dominant bacteria, and to determine their taxonomy and the physiological characteristics responsible for their adaptation to this environment. Groundwater samples contained high concentrations of acetate, oxalate, nitrate, and sulfate, as well as radionuclides. High-throughput sequencing and analysis of the clone libraries revealed lower microbial diversity in the most strongly contaminated groundwater and a predominance of bacteria of the genera Polynucleobacter, Pusillimonas, Candidatus Pelagibacter, and of the candidate phylum Parcubacteria; these groups include species with an ultra small cell size. Archaeal sequences in the libraries belonged to ammonium oxidizers of the phylum Thaumarchaeota and methanogens of the phylum Euryarchaeota. Pure cultures of obligate and facultative ultramicrobacteria belonging to the genera Chryseobacterium, Microbacterium, Salinibacterium, Pusillimonas, Roseomonas, and Janibacter were isolated from water samples. In genomes of Pusillimonas and Roseomonas strains the genes associated with nitrate reduction, resistance to heavy metals and metalloids were revealed. Several isolates are able to participate in the geochemical process of nitrate conversion to N2 using acetate; this results in decreasing redox potential, which in turn may stimulate radionuclide reduction and decrease radionuclide migration in groundwater.

Gut microbiota metabolism of functional carbohydrates and phenolic compounds from soaked and germinated purple rice

This study revealed that soaking and germination significantly reduced (P < 0.05) the glycemic index of purple rice (72.64 ± 0.75–61.52 ± 3.11%) and lowest value was observed with 24 h soaked sample. Non-digestible starch and phenolic metabolites in soaked purple rice could be correlated with the increased amount of Bifidobacterium (log 9.62–10.21), Lactobacillus (log 8.55–9.30) and significant decrease (P < 0.05) in growth of Clostridium/Enterobacter and Bacteroides groups during fecal fermentation. Furthermore, highest concentrations of acetate (35.27 ± 0.09 mM) and prebiotic index (PI) score of 0.79 was recorded with the soaked sample after 48 h. Phenolic metabolites including pyrocatechol, 3-(4-hydroxyphenyl) propionic acid, salicylic acid, trans-cinnamic acid and non-digestible carbohydrates metabolites were identified by LC-MS. Therefore, the soaked purple rice could be a potential functional hypoglycemic ingredient for management of gut health, diabetes, obesity and gut-brain diseases such as memory improvement in elderly.

Responses of Methanosarcina barkeri to acetate stress

BackgroundAnaerobic digestion of easily degradable biowaste can lead to the accumulation of volatile fatty acids, which will cause environmental stress to the sensitive methanogens consequently. The metabolic characteristics of methanogens under acetate stress can affect the overall performance of mixed consortia. Nevertheless, there exist huge gaps in understanding the responses of the dominant methanogens to the stress, e.g., Methanosarcinaceae. Such methanogens are resistant to environmental deterioration and able to utilize multiple carbon sources. In this study, transcriptomic and proteomic analyses were conducted to explore the responses of Methanosarcina barkeri strain MS at different acetate concentrations of 10, 25, and 50 mM.ResultsThe trend of OD600 and the regulation of the specific genes in 50 mM acetate, indicated that high concentration of acetate promoted the acclimation of M. barkeri to acetate stress. Acetate stress hindered the regulation of quorum sensing and thereby eliminated the advantages of cell aggregation, which was beneficial to resist stress. Under acetate stress, M. barkeri allocated more resources to enhance the uptake of iron to maintain the integrities of electron-transport chains and other essential biological processes. Comparing with the initial stages of different acetate concentrations, most of the genes participating in acetoclastic methanogenesis did not show significantly different expressions except hdrB1C1, an electron-bifurcating heterodisulfide reductase participating in energy conversion and improving thermodynamic efficiency. Meanwhile, vnfDGHK and nifDHK participating in nitrogen fixation pathway were upregulated.ConclusionIn this work, transcriptomic and proteomic analyses are combined to reveal the responses of M. barkeri to acetate stress in terms of central metabolic pathways, which provides basic clues for exploring the responses of other specific methanogens under high organics load. Moreover, the results can also be used to gain insights into the complex interactions and geochemical cycles among natural or engineered populations. Furthermore, these findings also provide the potential for designing effective and robust anaerobic digesters with high organic loads.

Metabolic, Physiological, and Transcriptomics Analysis of Batch Cultures of the Green Microalga Chlamydomonas Grown on Different Acetate Concentrations.

Acetate can be efficiently metabolized by the green microalga Chlamydomonas reinhardtii. The regular concentration is 17 mM, although higher concentrations are reported to increase starch and fatty acid content. To understand the responses to higher acetate concentrations, Chlamydomonas cells were cultivated in batch mode in the light at 17, 31, 44, and 57 mM acetate. Metabolic analyses show that cells grown at 57 mM acetate possess increased contents of all components analyzed (starch, chlorophylls, fatty acids, and proteins), with a three-fold increased volumetric biomass yield compared to cells cultivated at 17 mM acetate at the entry of stationary phase. Physiological analyses highlight the importance of photosynthesis for the low-acetate and exponential-phase samples. The stationary phase is reached when acetate is depleted, except for the cells grown at 57 mM acetate, which still divide until ammonium exhaustion. Surprisal analysis of the transcriptomics data supports the biological significance of our experiments. This allows the establishment of a model for acetate assimilation, its transcriptional regulation and the identification of candidates for genetic engineering of this metabolic pathway. Altogether, our analyses suggest that growing at high-acetate concentrations could increase biomass productivities in low-light and CO2-limiting air-bubbled medium for biotechnology.

Shewanella oneidensis NADH Dehydrogenase Mutants Exhibit an Amino Acid Synthesis Defect

Shewanella oneidensis MR-1 is a dissimilatory metal reducing bacterium with a highly branched respiratory electron transport chain. The S. oneidensis MR-1 genome encodes four NADH dehydrogenases, any of which may be used during respiration. We previously determined that a double-knockout of two NADH dehydrogenases, Nuo and Nqr1, eliminated aerobic growth in minimal medium. However, the double-knockout strain was able to grow aerobically in rich medium. Here, we determined that amino acid supplementation rescued growth of the mutant strain in oxic minimal medium. To determine the mechanism of the growth defect, we monitored growth, metabolism, and total NAD(H) pools in S. oneidensis MR-1 and the NADH dehydrogenase knockout strain. We also used a genetically encoded redox sensing system and determined that NADH/NAD+ was higher in the mutant strain than in the wild-type. We observed that the double-knockout strain was able to metabolize d,l-lactate and N-acetylglucosamine when supplemented with tryptone, but excreted high concentrations of pyruvate and acetate. The requirement for amino acid supplementation, combined with an apparent inability of the mutant strain to oxidize pyruvate or acetate suggests that TCA cycle activity was inhibited in the mutant strain by a high NADH/NAD+.

Effect of dietary graded resistant potato starch levels on growth performance, plasma cytokines concentration, and intestinal health in meat ducks.

The objective of the present study was to investigate the effect of dietary graded raw potato starch (RPS) levels on growth performance, plasma cytokines concentration, ileal barrier function, and cecal short-chain fatty acids (SCFA) concentration in meat ducks from 1 to 35 D of age. This study included 2 experiments. In experiment (Exp.) 1, sixteen 35-day-old meat ducks were used to evaluate the AME of RPS by orogastric administration. Results showed the AME value of RPS on ducks is 2.76kcal/g. In Exp. 2, a total of 600 one-day-old ducklings were randomly assigned to 5 isonitrogenous and isoenergetic dietary treatments that included 0 (control), 6, 12, 18, and 24% RPS, respectively. Samples were collected at both of 14 and 35 D. Neither growth performance nor ileal parameters (length, weight, and pH) at both of 14 and 35 D was affected by dietary RPS. However, the mucosal thickness (14 D), villus height (except for 18% RPS at 14 D), and the villus height: crypt depth ratio (14 and 35 D) of the ileum were increased in the 12 and 18% RPS diets when compared to 0% RPS diet. Meanwhile, proinflammatory factors such as plasma interleukin (IL)-1β and IL-6 (14 D) reduced in 12% RPS diet and tumor necrosis factor α decreased in 12% (except for 14 D) and 18% RPS groups. When compared with the control group, diets with 18% RPS significantly increased mucin 2 gene expression at 14 D, and 12% RPS elevated the mRNA expression of tight junction proteins including Zonula occludens-1 and Claudin 1 (except for 14 D) in the ileal mucosa of birds. Furthermore, ducks fed 12% RPS diet had higher concentrations of acetate, propionate, and butyrate in cecal digesta than other groups. These findings indicated that diets with 12 and/or 18% RPS increased the cecal SCFA concentration, which subsequently enhanced the barrier function and improved intestinal health in the ileum for 14 and 35-day-old meat ducks.

146 Effects of feeding soluble fiber (dextrin) to pigs pre- and post-weaning on growth performance and volatile fatty acid (VFA) production

Abstract Thirty-two barrows were used in a 35-d experiment with the objective of evaluating effects of supplemental soluble fiber (dextrin) pre- and post-weaning on growth performance and VFA production. Pigs were blocked by genetics and BW, and randomly allotted to treatments in a 2x2 factorial design with or without fiber pre-weaning and with or without fiber post-weaning. Fiber was suspended in chocolate milk and administered orally through a syringe from 14 d prior to weaning until 4 d post-weaning, after which it was included in the diet at 1%. At weaning, pigs were group housed by treatment and allowed ad libitum access to a common starter diet. On d 4 post-weaning, pigs were moved to individual pens and fed diets with or without 1% fiber. Weights and feed intake were recorded 14 and 3 d prior to weaning and on d 0, 4, 11, and 21 post-weaning. On d 21 post-weaning, pigs were euthanized, and large intestine contents were collected for VFA analysis. Data were analyzed using the GLM procedure of SAS with pig as the experimental unit. Growth performance was not affected (P &gt; 0.10) by treatment. A trend for an interaction of pre- and post-weaning fiber supplementation was observed for acetate (P = 0.052) and butyrate (P = 0.087) concentrations in large intestine contents. Pigs fed fiber only in the nursery had the highest acetate concentration, while pigs never receiving fiber had the lowest concentration. Pre-weaning fiber supplementation followed by no fiber in the nursery resulted in the highest butyrate concentrations with all other treatments being similar. Fiber supplementation pre-weaning tended (P = 0.053) to reduce isobutyrate concentrations. Pigs not receiving fiber post-weaning had increased valerate concentrations (P = 0.0245). There were no changes observed in propionate or isovalerate concentrations (P &gt; 0.10). Fiber supplementation caused alterations in VFA concentrations when fed during pre- and post-weaning, indicating possible shifts in the microbiome, immune status and barrier function of the intestinal tract.

Enhanced removal of pharmaceuticals in a biofilter: Effects of manipulating co-degradation by carbon feeding

Biofilm reactors are a promising biotechnology to eliminate pharmaceuticals from wastewater during tertiary treatment or in water works for drinking water production. This study aimed at investigating the effects of pulsed carbon feeding for promoting the co-degradation of indigenous pharmaceuticals from pre-treated wastewater in a fixed-bed porous biofilm reactor (slow sand filter). The addition of acetate (carbon source) resulted in three different enhancement/limitation effects, which were compound dependent: 1) atenolol and iohexol experienced enhanced co-degradation followed by constant (acetate independent) degradation; 2) metoprolol, iomeprol, diclofenac, propranolol and sulfamethizole co-degradation dependent on aerobic turnover, but inhibited at higher acetate concentrations (60–300 mg C/L); 3) sulfadiazine, sulfamethoxazole and trimethoprim were removed independently of oxygen and acetate concentration. Carbamazepine, ditriazoic acid, iopromide; tramadol and venlavaxine were not removed at any acetate dosage. Biofilm reactors can be employed for polishing treated wastewater, and the addition of a primary carbon source can enhance the performance of the bioreactor.

Trichostrongylus colubriformis infection: Impact on digesta passage rate and lamb performance

In this study we aimed to evaluate the effect of Trichostrongylus colubriformis infection on digesta passage rate, rumen fermentation and lamb performance. Eighteen three-month-old Santa Ines castrated male lambs (16.9 ± 1.43 kg of body weight) were randomly distributed in two experimental treatments: Infected with T. colubriformis (I, n = 9) and Uninfected (U, n = 9). The I lambs received a total of 45,000 L3 larvae of T. colubriformis (5,000 infective larvae, three times per week for three weeks). Daily feed intake was assessed using the I lambs as a reference for their respective pairs on the U group (pair-fed). Weight, body condition score and faeces (stool) samples were obtained every 15 days for 75 days. In both treatments, faecal egg count (FEC), digesta passage rate, rumen fermentation parameters, protozoa count and short chain fatty acids (SCFA) were evaluated. The lambs presented moderate infection (FEC = 620). The retention time of the digesta in the rumen-reticulum segment was lower (P < 0.05) in I lambs. The I lambs presented no inappetence, however, lower concentrations of total SCFA and butyrate, while higher acetate concentration were observed in these lambs (P < 0.05). The present findings highlight that T. colubriformis infection decreased the retention time (solid and liquid content) of the digesta in the rumen-reticulum, as well as negatively affected lamb growth.

Acetate Metabolism and the Inhibition of Bacterial Growth by Acetate.

During aerobic growth on glucose, Escherichia coli excretes acetate, a mechanism called "overflow metabolism." At high concentrations, the secreted acetate inhibits growth. Several mechanisms have been proposed for explaining this phenomenon, but a thorough analysis is hampered by the diversity of experimental conditions and strains used in these studies. Here, we describe the construction of a set of isogenic strains that remove different parts of the metabolic network involved in acetate metabolism. Analysis of these strains reveals that (i) high concentrations of acetate in the medium inhibit growth without significantly perturbing central metabolism; (ii) growth inhibition persists even when acetate assimilation is completely blocked; and (iii) regulatory interactions mediated by acetyl-phosphate play a small but significant role in growth inhibition by acetate. The major contribution to growth inhibition by acetate may originate in systemic effects like the uncoupling effect of organic acids or the perturbation of the anion composition of the cell, as previously proposed. Our data suggest, however, that under the conditions considered here, the uncoupling effect plays only a limited role.IMPORTANCE High concentrations of organic acids such as acetate inhibit growth of Escherichia coli and other bacteria. This phenomenon is of interest for understanding bacterial physiology but is also of practical relevance. Growth inhibition by organic acids underlies food preservation and causes problems during high-density fermentation in biotechnology. What causes this phenomenon? Classical explanations invoke the uncoupling effect of acetate and the establishment of an anion imbalance. Here, we propose and investigate an alternative hypothesis: the perturbation of acetate metabolism due to the inflow of excess acetate. We find that this perturbation accounts for 20% of the growth-inhibitory effect through a modification of the acetyl phosphate concentration. Moreover, we argue that our observations are not expected based on uncoupling alone.

Dehydrated apple‐based snack supplemented with Agave fructans exerts prebiotic effect regulating the production of short‐chain fatty acid in mice

The effect of dehydrated apple-based snack supplemented with Agave fructans on short-chain fatty acids (SCFA) production in mice was evaluated. Animals were randomly divided into three groups (n = 8): Control group (CG), oligofructose (OG), and Agave fructans (AG). After 24 days of treatment (stage 1), AG and OG showed elevated levels of acetate (10 µmol/g for both treatments), propionate (2.4 µmol/g for both treatments), and butyrate (1.5 and 3.2 µmol/g for OG and AG, respectively) compared with the CG. After 42 days of treatment (stage 2), AG had higher concentrations of acetate (20.8 µmol/g), propionate (2.1 µmol/g), and butyrate (5.5 µmol/g); whereas, OG only exhibited higher levels of acetate (16.8 µmol/g) and butyrate (5.6 µmol/g) in comparison with the controls. Dehydrated apple-based snack supplemented with Agave fructans exhibits a prebiotic effect increasing SCFA production in mice. Practical applications Dehydrated fruit-based snacks are generally perceived by consumers as healthy products with acceptable sensory attributes. They have a prolonged shelf life and may be consumed directly or cut into small parts for use in confectionery and bakery. In addition, the products derived from fruits plus prebiotics can enhance the beneficial effect on health and increase their consumption. This study opens up some commercial potential and technical challenges of using prebiotic-based supplements.

The impacts of Schizosaccharomyces on winemaking.

In the past century, yeasts from the genus Saccharomyces represented the only option in fermentation industries, such as winemaking, to produce wine, beer, and other fermented products. However, other genera are currently emerging to solve challenges in modern enology. Schizosaccharomyces pombe is showing promising results in solving specific challenges in northern, cool viticulture regions with highly acidic wines by deacidifying these wines through its malic acid metabolism. In addition, this microorganism is considered beneficial in warm growing regions with challenges such as the control of wine food safety problems such as the presence of biogenic amines, ochratoxin A, or ethyl carbamate. Indeed, the genus Schizosaccharomyces positively influences other important wine quality parameters, such as color and polysaccharide content. However, the main challenge of using this genus remains the selection of proper strains that alleviate problems such as the production of high acetate concentrations. Industries other than wine production such as ginger fermentation, apple wine, Kei-apple fermentation, plum wine, sparkling wine, and bilberry fermentation industries have also started to study Schizosaccharomyces species as an alternative tool for solving specific related problems. The review discusses the influence of Schizosaccharomyces on different fermentation quality parameters and its main applications in different industries.

Single chamber air\u2013cathode microbial fuel cells as biosensors for determination of biodegradable organics

ObjectivesSingle chamber air cathode microbial fuel cells (MFCs) were investigated with sodium-acetate and peptone as test substrates to assess the potential for application as biosensor to determine the concentration of biodegradable organics in water/wastewater samples.ResultsMFCs provided well-reproducible performance at high (> 2000 mg COD l−1—Chemical Oxygen Demand) acetate concentration values. Current in the cells proved to be steady from 25 to 35 °C, significant decrease was, however, revealed in the current below 20 °C. Direct calculation of non-toxic biodegradable substrate concentration in water/wastewater from the current in MFCs is possible only in the non-saturated substrate concentration range due to the Monod-like dependence of the current. This range was determined by a fitted and verified Monod-based kinetic model. Half saturation constant (KS) values were calculated at 30 °C applying different external resistance values (100 Ω, 600 Ω and 1000 Ω, respectively). In each case KS remained below 10 mg COD l−1.ConclusionsBiosensors with this particular MFC design and operation are potentially applicable for detecting as low as 5 mg COD l−1 readily biodegradable substrates, and measuring the concentration of these substances up to ~ 50–70 mg COD l−1.

Review: Brettanomyces yeasts in beer technology

Today, the use of non-standard types of yeast, which include Brettanomyces, is becoming increasingly popular in the food industry. They are tolerant to low pH, have a high-effective metabolism, and their ability to function in high concentrations of ethanol found application in the production of bioethanol. The most famous application of Brettanomyces is spontaneously fermented beer styles: lambic and gueuze. This beer is characterized by a long fermentation time (up to several years) and a rich, complex flavor with specific tones associated with a rich bacterial and fungal microflora. Volatile phenolic compounds in this beer, responsible for the main aromatic profiles associated with Brettanomyces: 4-ethylguaiacol, 4-ethylphenol, 4-ethylcatechol and their precursors 4-vinylguaiacol, 4-vinylphenol and 4-vinylcatechol. The proportion of ether in lambic beer is generally characterized by a low content of isoamyl acetate, a high concentration of ethylcaprylate and ethyl acetate and a significant amount of ethyl caprate.