Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “fermentation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed1999

Recovery of aroma compounds from a wine-must fermentation by organophilic pervaporation.

This study investigates the recovery of a wine-must aroma profile, formed by Saccharomyces cerevisiae during a muscatel wine-must fermentation, using organophilic pervaporation. Experiments were carried out along two independent, but organoleptically similar, fermentations. The wine-must samples and the aroma concentrates obtained were characterized organoleptically by a sensory panel and analytically with regard to eight major wine-must components: four alcohols; three esters; and one monoterpenic compound. Pervaporation performance was studied under fermentation conditions, and the permeate concentration, partial fluxes, and enrichment of the respective compounds were determined. The muscatel wine-must aroma profile was recovered purely and faithful to its origin between wine-must densities of 1075 and 1055 g L. At the beginning of the fermentation, too few aromas were present in the must for recovery. Toward the end of the fermentation, high ethanol concentrations in the wine-must caused a dramatic enrichment of two esters in the permeate, whereas other components investigated seemed unaffected. This shift resulted in an unbalanced aroma. In conclusion, it was shown that organophilic pervaporation can be highly suitable for the continuous recovery of very complex and delicate aromatic profiles produced during microbial fermentation. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗
PubMed2000

A kinetic study of the lactic acid fermentation. Batch process at controlled pH. Reprinted from Journal of Biochemical and Microbiological Technology Engineering Vol. I, No. 4. Pages 393-412 (1959).

Kinetic data are needed to develop basic understanding of fermentation processes and to permit rational design of continuous fermentation processes. The kinetics of the fermentation of glucose to lactic acid have been studied at six constant pH levels between 4. 5 and 6.0 by measuring the instantaneous rates of bacterial growth and of lactic acid formation throughout each fermentation. It was found that the instantaneous rate of acid formation dP/dt, should be related to the instantaneous rate of bacterial growth dN/dt, and to the bacterial density N, throughout a fermentation at a given pH, by the expression when the constants alpha and beta are determined by the pH of the fermentation.

Bioreactors↗
PubMed2003

Modeling of yeast metabolism and process dynamics in batch fermentation.

Much is known about yeast metabolism and the kinetics of industrial batch fermentation processes. In this study, however, we provide the first tool to evaluate the dynamic interaction that exists between them. A stoichiometric model, using wine fermentation as a case study, was constructed to simulate batch cultures of Saccharomyces cerevisiae. Five differential equations describe the evolution of the main metabolites and biomass in the fermentation tank, while a set of underdetermined linear algebraic equations models the pseudo-steady-state microbial metabolism. Specific links between process variables and the reaction rates of metabolic pathways represent microorganism adaptation to environmental changes in the culture. Adaptation requirements to changes in the environment, optimal growth, and homeostasis were set as the physiological objectives. A linear programming routine was used to define optimal metabolic mass flux distribution at each instant throughout the process. The kinetics of the process arise from the dynamic interaction between the environment and metabolic flux distribution. The model assessed the effect of nitrogen starvation and ethanol toxicity in wine fermentation and it was able to simulate fermentation profiles qualitatively, while experimental fermentation yields were reproduced successfully as well.

Adaptation, Physiological↗
PubMed2003

Fermentation monitoring using multisensor systems: feasibility study of the electronic tongue.

The electronic tongue based on an array of 30 non-specific potentiometric chemical sensors has been applied to qualitative and quantitative monitoring of a batch fermentation process of starting culture for light cheese production. Process control charts were built by using PLS regression and data from fermentations run under "normal" operating conditions. Control charts allow discrimination of samples from fermentation batches run under "abnormal" operating conditions from "normal" ones at as early as 30-50% of fully evolved fermentations. The capability of the electronic tongue to quantify concentrations of important organic acids (citric, lactic and orotic) in the present type of fermentation media was demonstrated. Average prediction errors were assessed in the range 5-13% based on test set validation. Correlation between peptide profiles determined using HPLC and the electronic tongue output was also established. The electronic tongue was demonstrated to be a promising tool for fermentation process monitoring and quantitative analysis of growth media.

Journal Article↗
PubMed1993

Tempe fermentation: some aspects of formation of gamma-linolenic acid, proteases and vitamins.

During a tempe fermentation the concentrations of linoleic, and alpha-linolenic acids (ALA) decreased while the concentration of oleic acid increased. During fatty acid synthesis Rhizopus sp. produced only gamma-linolenic acid (GLA) instead of ALA. The amount of GLA in tempe were influenced by varying external parameters. The proteolytic capacity of 36 strains of the genus Rhizopus isolated from Indonesian tempe or tempe inocula was examined. There was a distinct increase in the amount of free amino acids during tempe fermentation. Fermentations with mixed populations of bacteria and Rhizopus yielded a lower level of free amino acids, but an increase in total amount of amino acids. In comparison to intracellular, and extracellular proteases the proteases of the cell wall fraction are most responsible for proteolytic capacity of the different Rhizopus strains. Two isolated strains of Citrobacter freundii were found to be the best vitamin B(12) producers during the soaking of soybeans. In the solid substrate fermentation the Rhizopus molds formed vitamin B(6), riboflavin, and nicotinic acid. The addition of bacteria to the solid substrate fermentation resulted in a strong increase of active vitamin B(12) in tempe. In the presence of the Rhizopus mold, the vitamin B(12) formation by C. freundii was three times higher than that of a fermentation without the mold.

Journal Article↗
PubMed2006

Mucosal immunomodulation by the non-bacterial fraction of milk fermented by Lactobacillus helveticus R389.

The health promoting effects ascribed to probiotic bacteria and fermented dairy products arise not only from bacteria themselves but also from metabolites derived from milk fermentation. Exopolysaccharides produced during milk fermentation and peptides derived from major milk proteins, when released during fermentation, are potential modulators of various regulatory processes in the body. The aim of this work was to increase the knowledge of the previously observed immunomodulating capacity of milk fermented by Lactobacillus helveticus R389 by the study of the mucosal immunomodulation exerted by the non-bacterial fraction of the milk fermented at a constant pH6 (NBFpH6). The effects on IL-6 production by small intestine epithelial cells, the profile of IgA+ and cytokine+ cells (IL-2, IL-6, IL-10, TNF-alpha and IFN-gamma) induced in the gut lamina propria, and the levels of total and specific secretory IgA in the lumen of BALB/c mice that received NBFpH6 for 2, 5 or 7 days were examined. There was an increase in the number of IgA+, IL-10+, IL-2+ and IL-6+ cells after all feeding periods. Total S-IgA in the small intestine lumen increased in mice that received NBFpH6 for 2 days. However, no specific antibodies against NBFpH6 were detected. Feeding of NBFpH6 for 7 days significantly (P<0.05) enhanced IL-6 secretion by small intestine epithelial cells. NBFpH6 induced a non-specific mucosal response that was down-regulated for protective immunity, enhancing IL-6 production by epithelial cells and IgA production in the small intestine. These events improve the immunological defenses at the intestinal level, increasing host protection against pathologies. Because mucosal immune responses induced by certain dietary antigens play a large part in the prevention of gastrointestinal diseases, the oral administration of a mucosal adjuvant such as NBFpH6 may positively affect the milieu of the intestinal lumen. The opportunity exists then to manipulate the constituents of the lumen of the intestine through dietary means, thereby enhancing the health condition of the host.

Animals↗
PubMed2001

On-line monitoring and controlling system for fermentation processes.

A personal computer-based on-line monitoring and controlling system was developed for the fermentation of microorganism. The on-line HPLC system for the analysis of glucose and ethanol in the fermentation broth was connected to the fermenter via an auto-sampling equipment, which could perform the pipetting, filtration and dilution of the sample and final injection onto the HPLC through automation based on a programmed procedure. The A/D and D/A interfaces were equipped in order to process the signals from electrodes and from the detector of HPLC, and to direct the feed pumps, the motor of stirrer and gas flow-rate controller. The software that supervised the control of the stirring speed, gas flow-rate, pH value, feed flow-rate of medium, and the on-line measurement of glucose and ethanol concentration was programmed by using Microsoft Visual Basic under Microsoft Windows. The signal for chromatographic peaks from on-line HPLC was well captured and processed using an RC filter and a smoothing algorithm. This monitoring and control system was demonstrated to be effective in the ethanol fermentation of Zymomonas mobilis operated in both batch and fed-batch modes. In addition to substrate and product concentrations determined by on-line HPLC, the biomass concentration in Z. mobilis fermentation could also be on-line estimated by using the pH control and an implemented software sensor. The substrate concentration profile in the fed-back fermentation followed well the set point profile due to the fed-back action of feed flow-rate control.

Journal Article↗
PubMed2000

On-line parameter estimation of industrial fermentation process with an alkaliphilic cellulase-producing bacterium by exhaust gas analysis.

A method for on-line estimation of the fermentation parameters (substrate, product, and cells) of an alkaliphilic Bacillus sp. by utilizing data on the O2 and CO2 tensions in the exhaust gas and the pH of the fermentation broth was investigated. The estimation was based on the stoichiometric relations concerning the weight of CO2 formed, O2 consumed, product formed, and substrate consumed by the bacterium and on the ratio of the mass of the product to that of the cell biomass. During the fermentation, in which the pH range was 7.8-8.8, the parameters were successfully estimated by considering the reactions of CO2 to produce HCO3- and/or CO3(2-) in the liquid-phase as well as the desorption of CO2 to the aeration gas. It was verified that the proposed estimation method is applicable to industrial-scale fermentation using an alkaliphilic cellulase-producing Bacillus sp. The correlation coefficients between the estimated and observed fermentation parameters exceeded 0.990, indicating that the method is capable of evaluating fermentation parameters with an accuracy satisfactory for industrial use.

Journal Article↗
PubMed1998

Effect of fermented milk intake on plasmid transfer and on the persistence of transconjugants in the digestive tract of gnotobiotic mice.

Plasmid transfer occurs in the digestive tract and the transconjugants may become durably established. The aim of the present work is to investigate the effect of probiotics of plasmid transfer and on establishment of transconjugants in the gut. Plasmid transfers were carried out in the digestive tract of germ free mice associated with an E. coli K12 donor strain harboring three plasmids (R388, self-transmissible, pCE325 and pUB2380, mobilisable,) and an E. coli recipient strain, PG1, of human origin (Duval-Iflah et al., 1994). Milks fermented with either Lactobacillus bulgaricus or Streptococcus thermophilus or symbiosis, S85, of both strains were given daily as 1/3 of food diet. Fermented milks have no effect on the transfer of R388 and pUB2380 except a slight increase of TC(R388) with milk fermented with S85. Long term ingestion of milk fermented with S85 inhibited the formation and the establishment of transconjugants TC(pCE325). Milk fermented with L. bulgaricus lowered the population density of TC(pCE325) in animals where they were already established. This phenomenon was reversible, since the density of TC(pCE325) increased in the same animals after cessation of supplementation. Bacterial cultures obtained in MRS broth and given in state of drinking water were compared with fermented milks. Bacterial cultures with L. bulgaricus and with S85 favoured the establishment of TC(pCE325). There results indicate for the first time that probiotics have various effects on the formation and/or establishment of transconjugants in the gut of axenic mice. The effects depend on whether the probiotics were cultivated in milk or in MRS, indicating that bacterial metabolites and viable bacteria can be involved.

Animals↗
PubMed1999

Fermentation production of keratinase from Bacillus licheniformisPWD-1 and a recombinant B. subtilis FDB-29.

Fermentation scale-up was studied for the production of keratinase by Bacillus licheniformis PWD-1, the parent strain, and B. subtilis FDB-29, a recombinant strain. In both strains, keratinase was induced by proteinaceous media, and repressed by carbohydrates. A seed culture of B. licheniformis PWD-1 at early age, 6-10 h, is crucial to keratinase production during fermentation, but B. subtilis FDB-29 is insensitive to the seed culture age. During the batch fermentation by both strains, the pH changed from 7.0 to 8.5 while the keratinase activity and productivity stayed at high levels. Control of pH, therefore, is not necessary. The temperature for maximum keratinase production is 37 degrees C for both strains, though B. licheniformis is thermophilic and grows best at 50 degrees C. Optimal levels of dissolved oxygen are 10% and 20% for B. licheniformis and B. subtilis respectively. A scale-up procedure using constant temperature at 37 degrees C was adopted for B. subtilis. On the other hand, a temperature-shift procedure by which an 8-h fermentation at 50 degrees C for growth followed by a shift to 37 degrees C for enzyme production was used for B. licheniformis to shorten the fermentation time and increase enzyme productivity. Production of keratinase by B. licheniformis increased by ten-fold following this new procedure. After respective optimization of fermentation conditions, keratinase production by B. licheniformis PWD-1 is approximately 40% higher than that by B. subtilis FDB-29.

Journal Article↗
PubMed2004

Randomized placebo-controlled trial assessing the effect of bifidobacteria-fermented milk on active ulcerative colitis.

BACKGROUND: Probiotics are efficacious for treating and maintaining remission of ulcerative colitis. AIM: To conduct a randomized placebo-controlled trial of bifidobacteria-fermented milk supplementation as a dietary adjunct in treating active ulcerative colitis. METHODS: Twenty patients with mild to moderate, active, ulcerative colitis randomly received 100 mL/day of bifidobacteria-fermented milk or placebo for 12 weeks with conventional treatment. RESULTS: Clinical and endoscopic activity indices and histological scores were similar in the two groups before treatment. Although improvements were significant in both groups, the clinical activity index was significantly lower in the bifidobacteria-fermented milk than in the placebo group after treatment. The post-treatment endoscopic activity index and histological score were significantly reduced in the bifidobacteria-fermented milk, but not the placebo group. Increases in faecal butyrate, propionate and short-chain fatty acid concentrations were significant in the bifidobacteria-fermented milk, but not the placebo group. No adverse effects were observed in either group. CONCLUSION: Supplementation with this bifidobacteria-fermented milk product is safe and more effective than conventional treatment alone, suggesting possible beneficial effects in managing active ulcerative colitis. This is a pilot study and further larger studies are required to confirm the result these preliminary results.

Adult↗
PubMed1980

Antagonism between osmophilic lactic Acid bacteria and yeasts in brine fermentation of soy sauce.

Brine fermentation by osmophilic lactic acid bacteria and yeasts for long periods of time is essential to produce a good quality of shoyu (Japanese fermented soy sauce). It is well known that lactic acid fermentation by osmophilic lactic acid bacteria results in the depression of alcoholic fermentation by osmophilic yeasts, but the nature of the interaction between osmophilic lactic acid bacteria and yeasts in brine fermentation of shoyu has not been revealed. The inhibitory effect of osmophilic lactic acid bacteria on the growth of osmophilic yeasts was investigated. It was recognized that osmophilic shoyu yeasts such as Saccharomyces rouxii and Torulopsis versatilis were inhibited by a metabolite produced by osmophilic lactic acid bacteria (belonging to Pediococcus halophilus) in brine fermentation of shoyu. The primary inhibitor was considered to be acetic acid, although lactic acid was slightly inhibitory.

Journal Article↗
PubMed1982

Fermentation of Cellulose to Methane and Carbon Dioxide by a Rumen Anaerobic Fungus in a Triculture with Methanobrevibacter sp. Strain RA1 and Methanosarcina barkeri.

The fermentation of cellulose by a rumen anaerobic fungus in the presence of Methanobrevibacter sp. strain RA1 and Methanosarcina barkeri strain 227 resulted in the formation of 2 mol each of methane and carbon dioxide per mol of hexose fermented. Coculture of the fungus with either Methanobrevibacter sp. or M. barkeri produced 0.6 and 1.3 mol of methane per mol of hexose, respectively. Acetate, formate, ethanol, hydrogen, and lactate, which are major end products of cellulose fermentation by the fungus alone, were either absent or present in very low quantities at the end of the triculture fermentation (</=0.08 mol per mol of hexose fermented). During the time course of cellulose fermentation by the triculture, hydrogen was not detected (<1 x 10 atm; <0.001 kPa) and only acetate exhibited transitory accumulation; the maximum was equivalent to 1.4 mol per mol of hexose at 6 days which was higher than the total acetate yield of 0.73 in the fungus monoculture. The effect of methanogens is interpreted as a shift in the flow of electrons away from the formation of electron sink products lactate and ethanol to methane via hydrogen, favoring an increase in acetate, which is in turn converted to methane and carbon dioxide by M. barkeri. The maximum rate of cellulose degradation in the triculture (3 mg/ml per day) was faster than previously reported for bacterial cocultures and within 16 days degradation was complete. The triculture was used successfully also in the production of methane from cellulose in the plant fibrous materials, sisal (fiber from leaves of Agave sisalona L.) and barley straw leaf.

Journal Article↗
PubMed1985

Solid-state fermentation: an alternative to improve the nutritive value of coffee pulp.

Coffee pulp was subjected to a solid-state fermentation process, using Aspergillus niger. The initial moisture content of the pulp, as well as the fermentation time and temperature, had a significant effect on the increase in total amino acid content of the material. The increase in total amino acids showed a significant correlation with the dry matter recovered (r = -0.98) and the increase in pH during the process (r = 0.98). With a moisture content of 80%, a pH of 3.5, a temperature of 35 degrees C, and an aeration of 8 liters/min per kg as fermentation conditions, it was found that the maximum concentration of total amino acids was attained after 43 h. The fermented product had a higher total amino acid content and a lower cell wall constituent value (primarily cellulose and hemicellulose) than the original pulp. A growing chicken's ration containing 10% of the fermented product had a feed efficiency (2.14) similar to that of the standard ration (2.19) and was significantly better than that of the diet containing 10% of the original pulp (2.53). The difference observed in feed intake and weight gain between the standard diet and that with 10% of the fermented product is considered to be due to palatability factors which should be studied further.

Journal Article↗
PubMed1986

Growth and Metabolism of Lactic Acid Bacteria during and after Malolactic Fermentation of Wines at Different pH.

Commercially produced red wines were adjusted to pH 3.0, 3.2, 3.5, 3.7, or 4.0 and examined during and after malolactic fermentation for growth of lactic acid bacteria and changes in the concentrations of carbohydrates, organic acids, amino acids, and acetaldehyde. With one exception, Leuconostoc oenos conducted the malolactic fermentation in all wines and was the only species to occur in wines at pH below 3.5. Malolactic fermentation by L. oenos was accompanied by degradation of malic, citric, and fumaric acids and production of lactic and acetic acids. The concentrations of arginine, histidine, and acetaldehyde also decreased at this stage, but the behavior of hexose and pentose sugars was complicated by other factors. Pediococcus parvulus conducted the malolactic fermentation in one wine containing 72 mg of total sulfur dioxide per liter. Fumaric and citric acids were not degraded during this malolactic fermentation, but hexose sugars were metabolized. P. parvulus and species of Lactobacillus grew after malolactic fermentation in wines with pH adjusted above 3.5. This growth was accompanied by the utilization of wine sugars and production of lactic and acetic acids.

Journal Article↗
PubMed1986

Anaerobic fermentation of woody biomass pretreated with supercritical ammonia.

The degradability of ground hardwood by thermophilic anaerobic bacteria (Clostridium thermocellum with or without Thermoanaerobacter strain B6A) was greatly enhanced by pretreatment of the substrate with supercritical ammonia. Relative to C. thermocellum monocultures, cocultures of C. thermocellum and Thermoanaerobacter strain B6A degraded 1.5-fold more pretreated soft maple but produced 2- to 5-fold more fermentation endproducts because Thermoanaerobacter sp. removed reducing sugars produced by C. thermocellum during the fermentation. Dry weight losses were not totally accounted for in end products, due to formation of partially degraded material (<0.4 mum diameter wood particles) during the fermentation. One pretreated hardwood, Southern red oak, was fermented poorly because it released soluble inhibitors at the 60 degrees C incubation temperature. Considerable (6- to 11-fold) increases in substrate degradability were also noted for supercritical ammonia-pretreated wood materials fermented in an in vitro rumen digestibility assay. Degradation of pretreated softwoods by either thermophilic or mesophilic fermentation was not measurable under the conditions tested.

Journal Article↗
PubMed1987

Formation and fate of fermentation products in hot spring cyanobacterial mats.

The fate of representative fermentation products (acetate, propionate, butyrate, lactate, and ethanol) in hot spring cyanobacterial mats was investigated. The major fate during incubations in the light was photoassimilation by filamentous bacteria resembling Chloroflexus aurantiacus. Some metabolism of all compounds occurred under dark aerobic conditions. Under dark anaerobic conditions, only lactate was oxidized extensively to carbon dioxide. Extended preincubation under dark anaerobic conditions did not enhance anaerobic catabolism of acetate, propionate, or ethanol. Acetogenesis of butyrate was suggested by the hydrogen sensitivity of butyrate conversion to acetate and by the enrichment of butyrate-degrading acetogenic bacteria. Accumulation of fermentation products which were not catabolized under dark anaerobic conditions revealed their importance. Acetate and propionate were the major fermentation products which accumulated in samples collected at temperatures ranging from 50 to 70 degrees C. Other organic acids and alcohols accumulated to a much lesser extent. Fermentation occurred mainly in the top 4 mm of the mat. Exposure to light decreased the accumulation of acetate and presumably of other fermentation products. The importance of interspecies hydrogen transfer was investigated by comparing fermentation product accumulation at a 65 degrees C site, with naturally high hydrogen levels, and a 55 degrees C site, where active methanogenesis prevented significant hydrogen accumulation. There was a greater relative accumulation of reduced products, notably ethanol, in the 65 degrees C mat.

Journal Article↗
PubMed1989

Betaine fermentation and oxidation by marine desulfuromonas strains.

Two bacterial strains were dominant in anaerobic enrichment cultures with betaine (N,N,N-trimethylglycine) as a substrate and intertidal mud as an inoculum. One was a coccoid bacterium which was a trimethylamine (TMA)-fermenting methanogen similar to Methanococcoides methylutens. The other strain, a rod-shaped, gram-negative, motile bacterium, fermented betaine. On the basis of its ability to oxidize acetate and ethanol to CO(2) with sulfur as an electron acceptor, its inability to reduce sulfate and sulfite, its morphology, the presence of c-type cytochromes, and other characteristics, the isolated strain PM1 was identified as Desulfuromonas acetoxidans. Although only malate and fumarate were known as substrates for fermentative growth of this species, the type strain (DSM 684) also fermented betaine. Strain PM1 grew with a doubling time of 9.5 h at 30 degrees C on betaine and produced approximately 1 mol of TMA per mol of betaine, 0.75 mol of acetate, and presumably CO(2) as fermentation products but only in the presence of selenite (100 nM). In this fermentation, betaine is probably reductively cleaved to TMA and acetate, and part of the acetate is then oxidized to CO(2) to provide the reducing equivalents for the initial cleavage reaction. In the presence of sulfur, betaine was converted to TMA and presumably CO(2) with the formation of sulfide; then, only traces of acetate were produced.

Journal Article↗