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The objective of this study was to evaluate the nutritional changes in silages of four sorghum hybrids at different storage times. The design was a completely randomized in a 4 × 9 arrangement of plots with four replications. The four sorghum hybrids, Qualysilo, Chopper, Dominator, and Maxisilo, were allocated to the plots. In the subplots, sampling times were considered in fresh material and after 1, 3, 7, 14, 28, 56, 112, and 224 days of storage. The material was ensiled in experimental polyvinyl chloride silos and subsequently evaluated for chemical composition and fermentative profile over the nine different periods of the fermentation process. Crude protein was reduced by 1.21g/kg per day until the third day of fermentation. The levels of neutral detergent insoluble nitrogen and acid detergent insoluble nitrogen exceeded the upper limit of 311 g/kg of N. Of the studied silages, an NDF content of 734 g/kg was obtained in Maxisilo, which was higher than the other silages (average: 547 g/kg). Silage production can be achieved with the four materials; however, the Maxisilo sorghum provides silages of lower quality, with a DM content of less than 30%. The other materials fit into the nutritional profiles proposed by the literature, characterizing them as good quality silages. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effects of different proportions of cactus pear mucilage as a moistening additive on chemical composition, ammonia nitrogen, volatile fatty acids, microbial dynamics, fermentation losses, pH, and aerobic stability of corn grains in the form of silage throughout storage periods. The study was carried out in a completely randomized design with a factorial arrangement (5×2), with four replications. The factors corresponded to five forms of moistening for corn grain silage, 0, 5, 10, 20, and 40% of cactus pear mucilage (MA) associated or not with urea (U) in the level of 1.5% of DM. The lowest DM content was found in the silage moistened with 40% of cactus pear mucilage, and the greatest CP content was found in the same treatment but when urea was added. Lower contents of propionic and butyric acids were observed in the silages moistened with 5 and 10% of cactus pear without and with the addition of urea. Dry matter recovery was higher in the treatments with water and 10% of cactus pear. The use of urea affected the LAB population only at 15 d of silo opening, providing a bigger population (6.58 logs CFU g -1 ) when compared to silages without urea (6.27 logs CFU g -1 ). The lower concentrations of propionic and butyric acids observed in the silage moistened with 5 and 10% of cactus pear mucilage, regardless of the addition of urea. However, it is recommended to use 10% of cactus pear mucilage without the addition of urea, as it provides better indicators of good-quality silage. [ABSTRACT FROM AUTHOR]

BACKGROUND: The present study aimed to determine the optimal conditions for making wines by the carbonic maceration (CM) method. In this test, we attempted to identify the causes of the higher volatile acidity of some wines vinified by this method. Accordingly, we measured the development and speed of intracellular fermentation inside the whole grapes under different vinification conditions. RESULTS: An active fermentation of the must in the tanks produced by inoculation with active dry yeasts was more efficient for the process than the addition of exogenous carbon dioxide (CO2). In addition, in CM vinification, the moment of devatting had a great influence on the content of acetaldehyde and acetic acid in the whole grapes. CONCLUSION: Yeast inoculation in the tanks and control of the devatting time are technological tools that could play an important role in the characteristics of the wines produced by carbonic maceration, especially with respect to acetic acid content. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The yeast Lachancea thermotolerans is of significant biotechnological interest, and selected strains of this species have become commonly used starter cultures in wine fermentation. However, the impact of this species on wine is frequently limited by the rapid dominance of Saccharomyces cerevisiae strains which are better adapted to wine alcoholic fermentation conditions. Previous studies have shown that the major limiting factor for L. thermotolerans competitive performance in the wine ecosystem is oxygen availability, and not ethanol levels as had been previously suggested. Here we investigated the transcriptional response of L. thermotolerans to anaerobiosis in wine fermentation conditions. The data show that L. thermotolerans broadly redirects gene expression towards genes involved in central carbon metabolism, lipid metabolism, remodeling of the cell wall as well as autophagy. Furthermore, the induction of genes that are likely involved in the generation of lactate indicates a redirection of metabolic flux towards this metabolite. The data provide the first insight into the oxygen-dependent response of L. thermotolerans and suggest potential genetic targets to improve lactate production and/or anaerobic fermentation performance of this yeast. [ABSTRACT FROM AUTHOR]

The chemical composition and the presence of microorganisms in liquid silage of peach (Prunus pérsica) were evaluated. A completely randomized design with a 2 * 2 factorial arrangement, four treatments with two percentages of inclusion of molasses and ammonium sulfate was used: T1 (10% molasses - 1% SAM), T2 (10% molasses - 3% SAM), T3 (20% molasses - 1% SAM) and T4 (20% molasses - 2% SAM), with three replications, which were stored between 17 and 19 ° C. The physical-chemical composition of the fruit was determined, taking pH values and microbiological growth, bacterial morphology was characterized on blood agar and MacConkey agar. The organoleptic evaluation of the final silage is established as GOOD according to fermentation characteristics. The protein value increased in each of the treatments as the pH value decreased, associated with high microbial growths, improving the true protein of the food. There was growth of whitish and smooth colonies in blood agar with a predominance of Gram + and Gram - bacillary forms. Pink color - smooth surface colonies grew on MacConkey Agar only on day 0. Liquid peach silage with the addition of SAM increases protein values; and the addition of molasses improves the fermentative parameters such as pH stability. [ABSTRACT FROM AUTHOR]

BACKGROUND Lactic acid bacteria inocula have been developed over the years to improve the aerobic stability of silages. The aims of the study were to evaluate the effect of various conservation periods and the use of Lactobacillus hilgardii inoculum on aerobic stability, fermentative profile and microbial population of corn and sorghum silages. Trials were carried out on two corns and one sorghum crops. The crops were untreated or treated with L. buchneri (LB, application rate 300 000 cfu g−1 FM), L. hilgardii (LH, application rate 300 000 cfu g−1 FM) and a combination (LB + LH, application rate 150 000 cfu g−1 FM each). Silos were opened after 15, 30, 100 and 250 days of conservation, and the silages were analysed for fermentative profile, microbial count and aerobic stability. RESULTS: During conservation, the inocula influenced the fermentation profile. The use of LH increased the aerobic stability at 15 and 30 days in one out of three trials, while after 100 and 250 days, the presence of LB alone or with LH led to greater stability. In all the trials, the acetic acid content increased, the yeast count decreased and the aerobic stability increased during the conservation period. CONCLUSIONS: This study has shown that a long period in complete anaerobiosis reduced yeast count and improved aerobic stability in all silages. The addition of LB was confirmed to be a good option for increasing aerobic stability of silages, whereas the effect of LH alone or in combination with LB on aerobic stability was not consistent between trials. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In Euglena gracilis, wax ester fermentation produces ATP during anaerobiosis. Here, we report that anaerobic wax ester production is suppressed when the mitochondrial electron transport chain complex I is inhibited by rotenone, whereas it is increased by the uncoupler carbonyl cyanide m‐chlorophenylhydrazone (CCCP). The ADP/ATP ratio in anaerobic cells is elevated by treatment with either rotenone or CCCP. Gene silencing experiments indicate that acyl‐CoA dehydrogenase, electron transfer flavoprotein (ETF), and rhodoquinone (RQ) participate in wax ester production. These results suggest that fatty acids are synthesized in mitochondria by the reversal of β‐oxidation, where trans‐2‐enoyl‐CoA is reduced mainly by acyl‐CoA dehydrogenase using the electrons provided by NADH via the electron transport chain complex I, RQ, and ETF, and that ATP production is highly supported by anaerobic respiration utilizing trans‐2‐enoyl‐CoA as a terminal electron acceptor. [ABSTRACT FROM AUTHOR]

Abstract In the production of fuel ethanol from sugarcane in Brazilian biorefineries, one way to achieve lower production costs is the fermentation of sugars into ethanol at high temperatures (˜48 °C), which could lead to a decrease in: contamination levels, use of antibiotics, cooling costs, water usage, use of sulphuric acid in cell recycling, and energy used in distillation. Since Saccharomyces cerevisiae , the yeast species used in these biorefineries, cannot grow at these temperatures, alternative organisms need to be employed and one candidate is Kluyveromyces marxianus. Here, 20 strains belonging to this species were screened for their capacity to thrive at high temperatures (37, 45 and 48 °C) and under conditions relevant in the fuel ethanol industry: low pH (2.5), anaerobiosis, and high ethanol concentrations (up to 10%). The ethanol producing capacity of some strains was also evaluated and the ethanol yield on sugar quantified. Strains K. marxianus NCYC 3396 and UFV-3 stood out as potential microorganisms to be plugged into this industry (metabolic, evolutionary and reverse engineering will be required), since they grew better than the remaining ones under most of the conditions tested and produced ethanol at 48 °C with similar yields (0.40 g ethanol.g glucose−1) to those displayed by S. cerevisiae at 37 °C. Highlights • Four K. marxianus strains have potential to thrive in the presence of stressors found in the fuel ethanol industry in Brazil. • K. marxianus NCYC 3396 and UFV-3 were capable of growing anaerobically in complex medium. • K. marxianus NCYC 3396 and UFV-3 yielded 0.40 g ethanol.g glucose−1 at 48 °C in a synthetic medium. • Cell viability was severely jeopardized when K. marxianus UFV-3 was tested in a miniaturized industrial system above 40 °C. [ABSTRACT FROM AUTHOR]

Although the concept of ensiling large-round or large-square bales dates back to the late 1970s, many refinements have been made to both equipment and management since that time, resulting in much greater acceptance by small or mid-sized dairy or beef producers. This silage preservation technique is attractive to producers for several reasons, but the primary advantage is a reduced risk of weather damage to valuable forage crops compared with preservation as dry hay. Most core principles for making high-quality precisionchopped silages also apply to baled silages; among these, establishing and subsequently maintaining anaerobiosis are priorities. For baled silages, these priorities are critical, in part because recommended moisture concentrations (45 to 55%) are drier, and particle length is much longer. These factors act to restrict the rate and extent of silage fermentation, often resulting in less production of desirable fermentation acids and a greater (less acidic) final pH. Within this context, preservation of baled silages can be improved by applying polyethylene (PE) film wraps promptly, using an appropriate number of PE film layers (6 to 8), selecting a storage site free of sharp objects or other debris, and by monitoring wrapped bales closely for evidence of puncture, particularly by birds or vermin. Under certain conditions, such as those in which the bale moisture of highly buffered forages exceeds the recommended range, the heterogeneous nature of baled silages coupled with a restricted rate and extent of fermentation may increase susceptibility to clostridial activity compared with precision- chopped forages ensiled at comparable moisture concentrations. To date, research evaluating inoculants or other additives designed to improve the fermentation of challenging forages or aerobic stability has been limited, but should not be discontinued. Development of PE film embedded with an oxygen-limiting barrier has yielded positive results in some trials; however, most differences between these novel formulations and reputable commercial PE film have been related to decreases in yeast and mold counts at the surface layer. Related assessments of fermentation or nutritive value determined on a whole-bale basis have been less conclusive. Baled silages can be produced successfully by adhering to straightforward management principles; as such, this form of silage production is likely to remain popular for the foreseeable future. [ABSTRACT FROM AUTHOR]

Nowadays ethanol is considered an alternative to liquid fossil fuels, as a product of fermentation of sugars by Saccharomyces cerevisiae and other microorganisms. It is very important in the food, pharmaceutical and chemical industries. Prior studies show that the addition of certain amount of zeolite induces an increase in the ethanol/glucose yield. In this work, the effect of zeolite on the carbon flux of S. cerevisiae in different culture conditions is reported. An explanation for the effect of the zeolite on the yeast metabolism is offered. Results show a 20% increase in yield, thus lowering production costs and improving the use of raw materials, which would increase the possibilities of using alcohol as biofuel. [ABSTRACT FROM AUTHOR]

In anaerobiosis, the microalga Chlamydomonas reinhardtii is able to produce H2 gas. Electrons mainly derive from mobilization of internal reserves or from water through biophotolysis. However, the exact mechanisms triggering this process are still unclear. Our hypothesis was that, once a proper redox state has been achieved, H2 production is eventually observed., To avoid nutrient depletion, which would result in enhanced fermentative pathways, we aimed to induce long-lasting H2 production solely through a photosynthesis : respiration equilibrium. Thus, growing cells were incubated in Tris Acetate Phosphate (TAP) medium under low light and high chlorophyll content., After a 250-h acclimation phase, a 350-h H2 production phase was observed. The light-to-H2 conversion efficiency was comparable to that given in some reports operating under sulphur starvation. Electron sources were found to be water, through biophotolysis, and proteins, particularly through photofermentation. Nonetheless, a substantial contribution from acetate could not be ruled out. In addition, photosystem II ( PSII) inhibition by 3-(3,4-dichlorophenyl)-1,1-dimethylurea ( DCMU) showed that it actively contributed to maintaining a redox balance during cell acclimation., In appropriate conditions, PSII may represent the major source of reducing power to feed the H2 evolution process, by inducing and maintaining an ideal excess of reducing power. [ABSTRACT FROM AUTHOR]

Abstract: VFAs can be obtained from lignocellulosic agro-industrial wastes, sludge, and various biodegradable organic wastes as key intermediates through dark fermentation processes and synthesized through chemical route also. They are building blocks of several organic compounds viz. alcohol, aldehyde, ketones, esters and olefins. These can serve as alternate carbon source for microbial biolipid, biohydrogen, microbial fuel cells productions, methanisation, and for denitrification. Organic wastes are the substrate for VFA platform that is of zero or even negative cost, giving VFA as intermediate product but their separation from the fermentation broth is still a challenge; however, several separation technologies have been developed, membrane separation being the most suitable one. These aspects will be reviewed and results obtained during anaerobic treatment of slaughterhouse wastes with further utilisation of volatile fatty acids for yeast cultivation have been discussed. [Copyright &y& Elsevier]

Abstract: The impact of fermentative metabolism at low temperature on cell division of Bacillus cereus was studied. Fermentation at 37 °C had no influence on the division of bacteria. Aerobic cultures at 15 °C produced larger cells than at 37 °C, but cell division was normal. In fermentative cultures at 15 °C, no increase in CFU ml−1 was observed. However, A 600 increased, due to formation of long filaments. Transmission electronic microscopy and light microscopy with fluorescent staining showed several nucleic acid entities separated by a hydrophobic membrane, indicating that each filament contained several individual cells attached by peptidoglycan. When left in air at room temperature, one filament gave several daughter cells, this means that one CFU formed by one filament may represent a greater contamination potential than one CFU formed by a single cell. Division was observed in cultures at 15 °C with anaerobic respiration in the presence of nitrates. Possible filamentous growth must thus be taken into account to avoid underestimating B. cereus growth in vacuum or modified atmosphere packaged foods stored at low temperature. [Copyright &y& Elsevier]

Dynamic flux balance analysis was utilized to simulate the metabolic behaviour of initially fully respirative and respirofermentative steady-state cultures of Saccharomyces cerevisiae during sudden oxygen depletion. The hybrid model for the dynamic flux balance analysis included a stoichiometric genome-scale metabolic model as a static part and dynamic equations for the uptake of glucose and the cessation of respirative metabolism. The yeast consensus genome-scale metabolic model [Herrgård MJ et al. (2008) Nat Biotechnol 26, 1155-1160; Dobson PD et al. (2010) BMC Syst Biol 4, 145] was refined with respect to oxygen-dependent energy metabolism and further modified to reflect S. cerevisiae anabolism in the absence of oxygen. Dynamic flux balance analysis captured well the essential features of the dynamic metabolic behaviour of S. cerevisiae during adaptation to anaerobiosis. Modelling and simulation enabled the identification of short time-scale flux distribution dynamics under the transition to anaerobic metabolism, during which the specific growth rate was reduced, as well as longer time-scale process dynamics when the specific growth rate recovered. Expression of the metabolic genes was set into the context of the identified dynamics. Metabolic gene expression responses associated with the specific growth rate and with the cessation of respirative metabolism were distinguished. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study three industrial strains were inoculated into natural sugar cane juice containing 22, 30 and 35% (w/v) sucrose supplemented with nitrogen sources with differing structural complexities, which varied from a single ammonium salt (ammonium sulphate) to peptides (peptone), under aerobic and anaerobic conditions. At 30 °C, in shaken cultures, it was found that efficient sucrose utilization occurred only in media supplemented with a nitrogen source. In general, under agitation, supplementation with peptone led to more efficient fermentation compared with ammonium sulphate supplementation, with higher biomass accumulation and maintenance of cell viability. In a 35% (w/v) sucrose fermentation, under conditions with an inoculation of low cell density, nitrogen supplementation was required to obtain complete sucrose utilization, suggesting the possibility of producing wines with higher amounts of ethanol under working conditions that approach the limit of yeast alcohol tolerance. The results in this study have industrial relevance and they indicate that, under appropriate environmental and nutritional conditions, the commercial Brazilian yeast strains studied can efficiently use sugar, with high cell viability, even during very high gravity sucrose fermentation conditions. Copyright © 2012 The Institute of Brewing & Distilling [ABSTRACT FROM AUTHOR]

Abstract: The impact of anaerobiosis strategy on 1,3-propanediol production during cultivation of Clostridium butyricum VPI 1718 in different size bioreactors was studied. In batch trials with N2 gas infusion, the fermentation was successfully accomplished, regardless of initial glycerol concentration imposed and bioreactor geometry. However, in the absence of N2 continual sparging, significant variations concerning the biochemical response of the strain were observed. Specifically, at 1-L bioreactor, the absence of N2 infusion at high initial glycerol concentration induced lactate dehydrogenase activity and thus lactic acid synthesis, probably due to partial blockage of phosphoroclastic reaction caused by insufficient self-generated anaerobiosis environment. During fed-batch cultivation with continual N2 sparging, the strain produced ∼71gL−1 of 1,3-propanediol, whereas under self-generated anaerobiosis, 1,3-propanediol pathway was evidently restricted, as only 30.5gL−1 of 1,3-propanediol were finally produced. Apparently, N2 infusion strategy paired with bioreactor geometry can alter the biochemical behavior of the particular strain. [Copyright &y& Elsevier]

Abstract: The key process parameters of solid state enzymolysis for the generation of soluble sugar (SS) and bio-hydrogen production from corn stalk were optimized by the response surface methodology (RSM) based on a three factor-five level central composite design (CCD), respectively. The result showed that the optimal solid state enzymolysis condition from corn stalk was 47.7 °C, SCED of 0.054 g/g and 10.3 days for the maximum SS yield of 526 mg/g-TVS. Correspondingly, the optimal enzymolysis conditions from corn stalk appeared at 46.3 °C, SCED of 0.049 g/g and 7.5 days for the maximum hydrogen yield of 205.5 mL/g-TVS from the hydrolyzed substrate by the next dark fermentation. In addition, the bio-hydrogen production mechanism from corn stalk was preliminary investigated by XRD and SEM analyses. The results suggested that the solid state enzymolysis of substrate played a vital role in the effective conversion of corn stalk into bio-hydrogen by dark fermentation. [Copyright &y& Elsevier]

Manipulation of NADH-dependent steps, and particularly disruption of the las-located lactate dehydrogenase (ldh) gene in Lactococcus lactis, is common to engineering strategies envisaging the accumulation of reduced end products other than lactate. Reverse transcription-PCR experiments revealed that three out of the four genes assigned to lactate dehydrogenase in the genome of L. lactis, i.e., the ldh, ldhB, and ldhX genes, were expressed in the parental strain MG1363. Given that genetic redundancy is often a major cause of metabolic instability in engineered strains, we set out to develop a genetically stable lactococcal host tuned for the production of reduced compounds. Therefore, the ldhB and ldhX genes were sequentially deleted in L. lactis FI10089, a strain with a deletion of the ldh gene. The single, double, and triple mutants, FI10089, FI10089ΔldhB, and FI10089ΔldhBΔldhX, showed similar growth profiles and displayed mixed-acid fermentation, ethanol being the main reduced end product. Hence, the alcohol dehydrogenase-encoding gene, the adhE gene, was inactivated in FI10089, but the resulting strain reverted to homolactic fermentation due to induction of the ldhB gene. The three lactate dehydrogenase-deficient mutants were selected as a background for the production of mannitol and 2,3-butanediol. Pathways for the biosynthesis of these compounds were overexpressed under the control of a nisin promoter, and the constructs were analyzed with respect to growth parameters and product yields under anaerobiosis. Glucose was efficiently channeled to mannitol (maximal yield, 42%) or to 2,3-butanediol (maximal yield, 67%). The theoretical yield for 2,3-butanediol was achieved. We show that FI10089ΔldhB is a valuable basis for engineering strategies aiming at the production of reduced compounds [ABSTRACT FROM AUTHOR]

Abstract: Nature and survivability of microalgal population during growth and photofermentative hydrogen (H2) production was evaluated using acid-rich effluents generated from dark-fermentation. Microalgae enriched in presence of glucose showed the dominance of H2 producing Chlorella sp. (Consortia-A), while consortia under starvation had the dominance of Scenedesmus sp. and Diatoms (Consortia-B) with negligible H2 production. Further experiments with Consortia-A using acid-rich effluents of designed synthetic wastewater (DSW) and food waste (FW) showed higher H2 production in the former than the latter in both dark (DSW, 1.21 mmol; FW, 0.16 mmol) and photo (DSW, 5.22 mmol; FW, 1.24 mmol) fermentation. High acetate concentrations in DSW effluents favored H2 production over FW effluents. Substrate degradation was also higher in case of DSW than the FW sets. Microalgal population that dominanted in Consortia-B appears to have opted the lipid storing metabolic pathway evidencing 2% lipid that can be converted to biodiesel. The data represent a novel approach to exploiting microalgae for biohydrogen production at the expense of cheaper raw material like dark-fermentation effluents. [Copyright &y& Elsevier]

Abstract: Fermentative hydrogen production (FHP) has received a great R & D interest in recent decades, as it offers a potential means of producing H2 from a variety of renewable resources, even wastewater via a low energy continuous process. Various extracellular metabolites including ethanol, acetate, butyrate and lactate can be produced during the fermentation, building a complex metabolic network of the FHP. Except for the recognition of its complexity, the metabolic flux network has not been well understood. Studies on biochemical reactions and metabolic flux network associated with the FHP in anaerobic fermentation system have only been drawn attention in recent years. This review summarizes the biochemical reactions taking place in the metabolic network of FHP. We discuss how the key operation factors influence metabolism in the FHP process. Recently developed and applied technologies for metabolic flux analysis have been described. Future studies on the metabolic network to enhance fermentative hydrogen production by strict anaerobes are recommended. It is expected that this review can provide useful information in terms of fundamental knowledge and update technology for scientists and research engineers in the field of biological hydrogen production. [Copyright &y& Elsevier]

Se utilizaron cuatro búfalos (Bubalus bubalis) de la raza Mediterráneo, con edades promedio de 13 meses y peso vivo medio inicial de 300 ± 12 kg, para determinar las características fermentativas y la cinética ruminal en búfalos alimentados con heno de bermuda cruzada (Cynodon dactylon (L.) Pears) (70 %) y concentrado (30 %), formulado con maíz molido y harina de soya cruda integral (SC) o extrusada (SE). El pH fue inferior (P < 0.01) cuando se utilizó soya extrusada (6. 55) en relación con la cruda (6. 79). No hubo diferencias entre tratamientos, para la concentración de nitrógeno amoniacal en el rumen. Los valores medios fueron de 16.5 y 18.0 mg.dL-1 para los tratamientos con SC y SE, respectivamente. Las tasas de recambio líquido en el rumen se afectaron (P < 0.05) por el tipo de dieta, con medias de 6.17 % h-1 para SC y 7.85 % h-1 para SE. El volumen ruminal representó 13.3 -14.6 % del peso vivo de los búfalos, pero no difirió entre tratamientos. El horario de muestreo no influyó en el pH ni en las concentraciones totales de ácidos grasos de cadena corta (AGCC), ácido acético y butírico, pero el ácido propiónico fue en ascenso (P < 0.05) después de la alimentación de la mañana. Los resultados obtenidos indican que, en las condiciones experimentales establecidas, el uso de soya extrusada en el concentrado, con respecto a la soya cruda no afectó de forma significativa la fermentación, ni el volumen ruminal. Sin embargo, incrementó la tasa de recambio líquido. Los valores de pH se mantuvieron altos y estables y la concentración de amonio fue adecuada para los microorganismos del rumen. [ABSTRACT FROM AUTHOR]

Abstract: Genome-based Flux Balance Analysis (FBA) and steady-state isotopic-labeling-based Metabolic Flux Analysis (MFA) are complimentary approaches to predicting and measuring the operation and regulation of metabolic networks. Here, genome-derived models of Escherichia coli (E. coli) metabolism were used for FBA and 13C-MFA analyses of aerobic and anaerobic growths of wild-type E. coli (K-12 MG1655) cells. Validated MFA flux maps reveal that the fraction of maintenance ATP consumption in total ATP production is about 14% higher under anaerobic (51.1%) than aerobic conditions (37.2%). FBA revealed that an increased ATP utilization is consumed by ATP synthase to secrete protons from fermentation. The TCA cycle is shown to be incomplete in aerobically growing cells and submaximal growth is due to limited oxidative phosphorylation. An FBA was successful in predicting product secretion rates in aerobic culture if both glucose and oxygen uptake measurement were constrained, but the most-frequently predicted values of internal fluxes yielded from sampling the feasible space differ substantially from MFA-derived fluxes. [ABSTRACT FROM AUTHOR]

The earthworm gut provides ideal in situ conditions for ingested heterotrophic soil bacteria capable of anaerobiosis. High amounts of mucus- and plant-derived saccharides such as glucose are abundant in the earthworm alimentary canal, and high concentrations of molecular hydrogen (H2) and organic acids in the alimentary canal are indicative of ongoing fermentations. Thus, the central objective of this study was to resolve potential links between fermentations and active fermenters in gut content of the anecic earthworm Lumbricus terrestris by 16S ribosomal RNA (rRNA)-based stable isotope probing, with [13C]glucose as a model substrate. Glucose consumption in anoxic gut content microcosms was rapid and yielded soluble organic compounds (acetate, butyrate, formate, lactate, propionate, succinate and ethanol) and gases (carbon dioxide and H2), products indicative of diverse fermentations in the alimentary canal. Clostridiaceae and Enterobacteriaceae were users of glucose-derived carbon. On the basis of the detection of 16S rRNA, active phyla in gut contents included Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria, Tenericutes and Verrucomicrobia, taxa common to soils. On the basis of a 16S rRNA gene similarity cutoff of 87.5%, 82 families were detected, 17 of which were novel family-level groups. These findings (a) show the large diversity of soil taxa that might be active during gut passage, (b) show that Clostridiaceae and Enterobacteriaceae (fermentative subsets of these taxa) are selectively stimulated by glucose and might therefore be capable of consuming mucus- and plant-derived saccharides during gut passage and (c) indicate that ingested obligate anaerobes and facultative aerobes from soil can concomitantly metabolize the same source of carbon. [ABSTRACT FROM AUTHOR]

The article focuses on the metabolic capabilities of two eurytopic organisms geomyces pannorum strains under different anaerobiosis conditions. It states that geomyces fungi are organisms with wide species distribution area that has the aptitude to grow and figure the fermentation products that were associated by increase of lactate and acetate. It mentions that the strain that was secluded from cryopeg water and from the hair of bank vole cletrionomys glareolus were the objects of the study.

During a general survey of the acetaldehyde-producing properties of commercially available wine yeast strains, we discovered that, although final acetaldehyde production cannot be used as a discriminating factor between yeast strains, initial specific acetaldehyde production rates were of highly interest for classifying yeast strains. This parameter is very closely related to the growth- and fermentation-lag phase durations. We also found that this acetaldehyde early production occurs with very different extent between commercial active dry yeast strains during the rehydration phase and could partially explain the known variable resistance of yeast strains to sulfites. Acetaldehyde production appeared, therefore, as very precocious, strain-dependent, and biomass-independent character. These various findings suggest that this new intrinsic characteristic of industrial fermenting yeast may be likely considered as an early marker of the general fermenting activity of industrial fermenting yeasts. This phenomenon could be particularly important for understanding the ecology of colonization of complex fermentation media by Saccharomyces cerevisiae. [ABSTRACT FROM AUTHOR]

The spreading of vinasse on soils may favor not only anoxia but also mineral alterations and metal mobilization. Our aims were to record the geochemical changes occurring in a ferralsol subjected to vinasse input and anaerobiosis, and to check for soil resilience after a return to aerobic conditions. Soil slurries were therefore incubated under successive 7 d of aerobic, 0 to 28 d of anaerobic, and 28 d of aerobic conditions, vinasse being supplied at one of three levels when anaerobiosis began. At several dates, the slurry solution was characterized (pH and organic and mineral compounds) and Mn and Fe oxidation states in solids were assessed. Before incubations, about 20% ofthe Fe in solids was already reduced, whereas almost all Mn was found as Mn(IV). During the first aerobic period, mobilized metals included Pb, Zn, Ni, Cu, and Cr. After vinasse input during the first 14 d of anaerobiosis, the principal biotransformations were fermentation and true acetogenesis; Fe and Mn were mobilized during this period (up to 4.05 and 6.2 mmol L-1, respectively), and most Mn and an unknown but small fraction of Fe in solids were reduced. During the subsequent 14 d of anaerobiosis, only acetoclastic methanogenesis was observed. The return to aerobic conditions led to rapid oxidative immobilization of Fe, desorption of exchangeable Fe(II), and the partial immobilization of other metals (Ca, Mg, K, Na, Mn, Pb, and Ni). Manganese was not oxidized, and there was no return to the initial conditions for Fe and Mn in solids. [ABSTRACT FROM AUTHOR]

Abstract: Intestinal microbes live in diminished or deprived oxygen conditions. Facultative anaerobic bacteria of the family Enterobacteriaceae ferment glucose in the gut using two main pathways: mixed acid and neutral fermentations. The aim of the present study was to clarify the roles of these fermentations in an in vitro model. Acid-producing Escherichia coli ATCC 25922 and neutral end-products producing Klebsiella mobilis ATCC 13048 were cultured in a Portable Microbe Enrichment Unit (PMEU) which permitted the selection of the gas phase in standardized conditions. In the butanediol production experiments also Klebsiella pneumoniae ssp. pneumoniae IIIa2 E111 strain was also used. Two isomers of 2,3-butanediol were observed in both aerobic and microaerobic Klebsiella cultures. During 7h cultures both E. coli and K. mobilis grew from densities of some million up to some billions per ml. The growth was almost equal in both aerobic and microaerobic conditions. In anaerobic conditions a balance prevailed in mixed E. coli and Klebsiella cultures between the species (final pH was 5.8–6.1), whereas in aerobic conditions the klebsiellas were favoured, and the pH rose up to about 8.5 (in 20h) as in pure Klebsiella cultures. In microaerobic Klebsiella cultures the final pH varied between 6.7 and 7.5. In mixed cultures the growth yields of both bacteria equalled those of the separate pure cultures indicating mutual benefits of the co-existence. Apparently E. coli produced a set of organic acids, which lowered pH. Klebsiellas increased the pH up to 2units probably due to acid conversion in anaerobic conditions to ethanol. We propose that the balance of acid and ethanol as well 2,3-butanediol fermentations contributes to the small bowel pH regulation, which also aids the host in the nutrient uptake in the small intestine. [Copyright &y& Elsevier]

Abstract: Microbial fermentation is a potentially important member of a diverse portfolio of methods available for renewable production of hydrogen using biomass as a substrate. A major factor currently limiting commercial viability of fermentative hydrogen production is poor stoichiometric yield per mole of sugar and end-product feedback inhibition. Although several approaches have been tried to enhance microbial hydrogen productivity, genetic engineering technologies for most promising microorganisms are either unavailable or severely limited. Further efforts to overcome existing issues will need to rely on the ability to analyze, predict and engineer microbial metabolism in native H2-producing strains as well as genetically engineerable strains with constructed H2-metabolism. A shift in the type of biomass substrate from starch-based food crops to ligno-cellulosic crops and wastes that are economically and environmentally less costly to produce, yet more difficult to chemically and biologically process, presents technical challenges that are shared by all emerging biofuel technologies. A brief overview of the current status of fermentative H2-production, including a discussion of directly and indirectly related emerging technologies, is presented. [Copyright &y& Elsevier]

During experiments to determine the effects of exogenously added acetaldehyde on pure cultures of various yeast strains, we discovered that an early acetaldehyde perfusion during the growth phase allowed several yeasts to partially overcome the phenotypic effects of zinc depletion during alcoholic fermentation. We, therefore, performed genome-wide expression and proteomic analysis on an industrial Saccharomyces cerevisiae yeast strain (VL1) growing in zinc-replete or zinc-depleted conditions in the presence of perfused acetaldehyde to identify molecular markers of this effect. Zinc depletion severely affects ethanol production and therefore nicotinamide adenine dinucleotide (NAD) regeneration, although we observed partial compensation by the upregulation of the poorly efficient Fe-dependent Adh4p in our conditions. A coordinate metabolic response was indeed observed in response to the early acetaldehyde perfusion, and particularly of the lower part of glycolysis, leading to the cellular replenishment of NAD cofactor. These various findings suggest that acetaldehyde exchange between strains may inhibit the growth of some yeast strains while encouraging the growth of others. This phenomenon could be particularly important for understanding the ecology of colonization of complex fermentation media by S. cerevisiae after elimination of non- Saccharomyces yeasts. [ABSTRACT FROM AUTHOR]

Summary: The relationship between coleoptile elongation and ethanolic fermentation was investigated in rice (Oryza sativa L.) coleoptiles of four cultivars subjected to a 48-h anoxic stress. The coleoptile elongation of all cultivars was suppressed by anoxic stress; however, the elongation of cvs Yukihikari and Nipponbare was much greater than that of cvs Leulikelash and Asahimochi. The stress did not significantly increase lactate dehydrogenase (LDH) activity or lactate concentration, but increased alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) activities, as well as ethanol concentration in the coleoptiles of all cultivars. The elevated ADH and PDC activities and ethanol concentration in cvs Yukihikari and Nipponbare were much greater than those of cvs Leulikelash and Asahimochi, suggesting that ethanolic fermentation is likely more active in cvs Yukihikari and Nipponbare than in cvs Leulikelash and Asahimochi. ATP concentration in cvs Yukihikari and Nipponbare in anoxia was also greater than that in cvs Leulikelash and Asahimochi in anoxia. The ethanol concentration in the coleoptiles was correlated with anoxia tolerance with respect to the ATP concentration and coleoptile elongation. These results suggest that the ability to increase ethanolic fermentation may be one of the determinants in anoxia tolerance of rice coleoptiles. [Copyright &y& Elsevier]

Low O2 stress to a varied extent affects almost all the organisms either throughout or at specific stages in their life cycle. Plants experience this stress generally in field conditions when flooding, submergence or waterlogging of roots/plants occurs. Low O2 availability during flooding stress results in enormous yield losses in variety of crops. There is overwhelming evidence indicating that adaptations to low O2 stress involves changes in molecular, biochemical, physiological, genetical and anatomical/morphological attributes in plants. Most plants respond to anaerobiosis by switching their respiration from the oxidative (involving complete oxidation of pyruvate into CO2) to the fermentation (involving incomplete oxidation of pyruvate into lactate/ethanol) pathway. Fermentation pathway-related proteins (such as pyruvate decarboxylase and alcohol dehydrogenase enzymes) have been characterized to a significant extent. However, attempts made in altering levels of pyruvate decarboxylase and alcohol dehydrogenase proteins in transgenic plants have not yielded significantly enhanced levels of low O2 /flooding stress tolerance as yet. Applying modern tools of transcriptome and proteome analysis, mechanism(s) responsible for low O2 /flooding stress tolerance phenotype are being addressed. Progress made in understanding plant responses to low O2 stress is herewith discussed. [ABSTRACT FROM AUTHOR]

The effect of decreasing oxygen feed rates on the growth and metabolism ofTorulaspora delbrueckiiandSaccharomyces cerevisiaein chemostat cultures was investigated. The biosynthetic oxygen requirement, i.e. the minimum specific oxygen consumption rate required for steady-state growth at a dilution rate of 0.10 h-1, ofT. delbrueckiiwas quantified to be less than 0.1 mmol O2 g-1 h-1. Under strict anaerobiosis, washout ofT. delbrueckiioccurred, whereas forS. cerevisiaeit did not. Under oxygen-limited conditions, the increase in fermentative ability ofT. delbrueckiiwith diminishing oxygen supply was less pronounced than that ofS. cerevisiae. These results indicate thatT. delbrueckiiwas more disturbed in its energy balance thanS. cerevisiaeunder strict anaerobiosis, and they may explain whyT. delbrueckiiexhibits poorer growth thanS. cerevisiaeunder this condition. [ABSTRACT FROM AUTHOR]

Stem segments from terminal leaders of Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco, seedlings were sampled in mid‐December when cambial cells were dormant. The residual, debudded leaders were resampled again in early May when the cambium was metabolically active. May stems had higher constitutive ethanol concentrations than December stems. This was not the result of cambial hypoxia generated by rapid spring respiration rates, because when aerobic respiration was stimulated by incubating the stems in air at 30 °C ethanol production was induced in December, but not in May. Rapid respiration rates at 30 °C may have depleted O2 supplies and induced ethanol production in December stems because dormant, thick‐walled cambial cells may be less permeable to CO2 and O2, compared with metabolically active, thin‐walled cambial cells in May. December stem segments incubated in a N2 atmosphere at 30 °C synthesized 1.8 times more ethanol than segments from May, most likely because spring growth had reduced the soluble sugars available for fermentation. CO2 efflux from May stems (after 5.5 h of incubation at 30 °C) was equal to December stems per unit volume, but greater than December stems per unit surface area. N2‐induced ethanol concentrations were positively related with CO2 efflux per unit volume, indicating that rapidly respiring leaders can maintain rapid fermentation rates, provided soluble sugars are readily available. N2‐induced ethanol and CO2 efflux per unit volume declined with increasing leader diameter in both seasons, whereas there were no relationships between CO2 efflux per unit surface area and diameter. Cambium physiology and phenology influence the induction of fermentation and concentrations of ethanol produced in terminal leaders of Douglas‐fir, and probably other conifers as well. This needs to be considered when comparing fermentation among species, or comparing individuals from different seasons, or disparate ages within a species. [ABSTRACT FROM PUBLISHER]

Following incubation of mesophilic methanogenic floccular sludge from a lab-scale upflow anaerobic sludge bed reactor used to treat cattle manure wastewater, a stable 5-aminosalicylate-degrading enrichment culture was obtained. Subsequently, a Citrobacter freundii strain, WA1, was isolated from the 5-aminosalicylate-degrading methanogenic consortium. The methanogenic enrichment culture degraded 5-aminosalicylate completely to CH4, CO2 and NH4+, while C. freundii strain WA1 reduced 5-aminosalicylate with simultaneous deamination to 2-hydroxybenzyl alcohol during anaerobic growth with electron donors such as pyruvate, glucose or serine. When grown on pyruvate, C. freundii WA1 converted 3-aminobenzoate to benzyl alcohol and also reduced benzaldehyde to benzyl alcohol. Pyruvate was fermented to acetate, CO2, H2 and small amounts of lactate, succinate and formate. Less lactate (30%) was produced from pyruvate when C. freundii WA1 grew with 5-aminosalicylate as co-substrate. [ABSTRACT FROM AUTHOR]

Abstract Aims: Yeast strains, used in the brewing industry, experience distinctive physiological conditions. During a brewing fermentation, yeast are exposed to anaerobic conditions, high pressure, high specific gravity and low temperatures. The purpose of this study was to examine the global gene expression profile of yeast subjected to brewing stress. Methods and Results: We have carried out a microarray analysis of a typical brewer's yeast during the course of an 8-day fermentation in 15°P wort. We used the probes derived from Saccharomyces cerevisiae genomic DNA on the chip and RNA isolated from three stages of brewing. This analysis shows a high level of expression of genes involved in fatty acid and ergosterol biosynthesis early in fermentation. Furthermore, genes involved in respiration and mitochondrial protein synthesis also show higher levels of expression. Conclusions: Surprisingly, we observed a complete repression of many stress response genes and genes involved in protein synthesis throughout the 8-day period compared with that at the start of fermentation. Significance and Impact of the Study: This microarray data set provides an analysis of gene expression under brewing fermentation conditions. The data provide an insight into the various metabolic processes altered or activated by brewing conditions of growth. This study leads to future experiments whereby selective alterations in brewing conditions could be introduced to take advantage of the changing transcript profile to improve the quality of the brew. [ABSTRACT FROM AUTHOR]

Organic matter transformations take place in snow-covered soils during winter but in ways still poorly understood. Given the generally high soil water content and possible formation of ice layers during this period, anaerobic zones could develop and have determinant effects on soil C and N dynamics. The fate of C and N under wet and cold conditions was monitored in a sandy loam and a clay soil which were either unamended (control) or amended with cattle manure, pig slurry, maize or alfalfa residues. Soil samples were incubated for 84 d during winter at constant water potential (−6 kPa) in sealed containers laid on the floor of an unheated greenhouse. The containers were covered with fibre glass wool to simulate a snow cover. The O2, CO2 and N2O concentrations were periodically monitored in the headspace of the containers, whereas K2SO4-extractable C, KCl-extractable NO3− and NH4+, and volatile fatty acids were quantified in soil sub-samples. Despite the low soil temperature (average of 1 °C), O2 consumption and CO2 production rates were significantly (P<0.05) increased by the amendments for the first 29 d of incubation. After 29 d, the O2 concentration fell below 6% and CO2 production rate decreased in all amended soils. We assumed that after 29 d aerobic respiration was replaced with fermentation processes in amended soils as indicated by respiratory quotients generally larger than 2, and by the progressive accumulation of volatile fatty acids. As O2 was consumed in sealed containers, nitrification decreased whereas ammonification continued and N2O production increased. As a result, soil NH4+ content increased whereas NO3− content was progressively depleted. After complete exhaustion of NO3−, the accumulated N2O disappeared and was probably reduced to N2. All measured parameters indicated that pig slurry and alfalfa stimulated soil microbial activities more than cattle manure and maize residues and these differences were partly related to the lignin-to-N ratio of the various amendments. Our data indicated that (i) significant C and N transformations occurred during winter in wet and cold soils amended with organic residues, (ii) under these conditions C and N dynamics were strongly influenced by O2 availability, and (iii) the rates at which C and N transformations occurred were partly determined by both C degradability and N availability of the organic amendments. [Copyright &y& Elsevier]

Ethylene production of iris bulbs (Iris hollandica cv. Ideal) was very low. When stored at 30°C, production was 12-20 pmol C2H4 (kg fresh weight)-1 h-1. Higher temperatures (35°C, 40°C) enhanced the ethylene production; a treatment with 40°C for ca 7 days caused a 3 times higher ethylene production than at 30°C. During anaerobic storage (in 100% N2) ethylene production was equal to that of control bulbs. When after a 7 day period of anaerobiosis the N2 was replaced by air, a burstlike ethylene production was observed. Twenty-four h after the replacement, ethylene production was equal to control values again. The effects of this production of ethylene on mitochondrial respiration and flowering were investigated. When mitochondria were isolated immediately after the anaerobic treatment (before the enhanced ethylene production) alternative pathway capacity was not detectable, a situation also occurring in control bulbs. When mitochondria were isolated 24 h after the end of the anaerobiosis (after the ethylene burst) uninhibited respiration did not change significantly, but a capacity of the alternative pathway was observed. The increase in alternative pathway capacity after anaerobiosis was partly inhibited by 2,5-norbornadiene (NBD), an ethylene antagonist. Fermentation occurred during anaerobiosis: ethanol concentrations increased during the treatment and decreased when air was supplied. When bulbs were exposed to ethanol vapour the alternative pathway was induced but only when very high ethanol levels in the bulbs were reached. The amount of ethanol accumulated in the bulbs during a 7 day anaerobic treatment was far too low to explain the observed induction of alternative pathway capacity. Flowering percentages were enhanced after a 24 h treatment with ethylene and after a 7 day anaerobic treatment. NBD significantly inhibited the effect of exogenous ethylene and of anaerobiosis on flowering. Ethanol was not able to induce flowering. The burst-like production of ethylene after anaerobiosis probably is responsible for the effects on respiration and flowering. [ABSTRACT FROM AUTHOR]

The tolerance of germinating rice seedlings to anaerobiosis cannot be fully accounted for by ethanolic fermentation alone. Nitrate metabolism (nitrate reduction to NH4+ plus its subsequent assimilation) may provide an additional sink mechanism for excess protons and NADH produced during anaerobiosis. To follow the fate of nitrate, 15N-labelled nitrate and ammonium incorporation in aerobic and anaerobic rice coleoptiles was examined using 15N-edited 1H NMR and gas chromatography-mass spectrometry methods. After 22 h of treatments, protein-free Ala, Glu, Gln, and γ-aminobutyrate were the main 15N-labelled products for both nitrate and ammonium-treated anaerobic rice coleoptiles, with Gln, Glu, and Ala being the most enriched. The total amount of 15N label incorporation into Ala and GAB increased significantly in response to anaerobiosis. The 15N-labelling pattern of Glu and Gln suggests that the GS/GOGAT system was primarily involved in ammonium assimilation whereas Glu dehydrogenase may play a role in nitrate assimilation. 15N incorporation into protein-dried amino acids was also significant and was more substantial in anaerobic than in aerobic rice coleoptiles, which indicate that protein biosynthesis remained active in anaerobic rice coleoptiles. Thus, anaerobic assimilation of inorganic N into amino acids, particularly Ala and Glu/GAB, may serve to supplement ethanolic fermentation in sustaining glycolysis and energy production in rice coleoptiles. [ABSTRACT FROM PUBLISHER]

Glucose-grown cells of Bacillus cereus respond to anaerobiosis and low extracellular oxidoreduction potentials (ORP), notably by enhancing enterotoxin production. This response involves the ResDE two-component system. We searched the B. cereus genome for other redox response regulators potentially involved in this adaptive process, and we identified one gene encoding a protein predicted to have an amino acid sequence 58% identical (80% similar) to that of the Bacillus subtilis Fnr redox regulator. The fnr gene of the food-borne pathogen B. cereus F4430/73 has been cloned and partially characterized. We showed that fnr was up-regulated during anaerobic fermentation, especially when fermentation occurred at low ORP (under highly reducing conditions). The expression of fnr was down-regulated in the presence of O2 and nitrate which, unlike fumarate, stimulated the respiratory pathways. The inactivation of B. cereus fnr abolished fermentative growth but only moderately affected aerobic and anaerobic nitrate respiratory growth. Analyses of glucose by-products and the transcription profiles of key catabolic genes confirmed the strong regulatory impact of Fnr on B. cereus fermentative pathways. More importantly, the fnr mutation strongly decreased the expression of PlcR-dependent hbl and nhe genes, leading to the absence of hemolysin BL (Hbl) and nonhemolytic enterotoxin (Nhe) secretion by the mutant. These data indicate that fnr is essential for both fermentation and toxinogenesis. The results also suggest that both Fnr and the ResDE two-component system belong to a redox regulatory pathway that functions at least partially independently of the pleiotropic virulence gene regulator PlcR to regulate enterotoxin gene expression. [ABSTRACT FROM AUTHOR]