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 1,387 records · Page 77Linked to original sources
PubMed2001

Influence of killer strains of Saccharomyces cerevisiae on wine fermentation.

The effect of killer strains of Saccharomyces cerevisiae on the growth of sensitive strains during must fermentation was studied by using a new method to monitor yeast populations. The capability of killer yeast strains to eliminate sensitive strains depends on the initial proportion of killer yeasts, the susceptibility of sensitive strains, and the treatment of the must. In sterile filtered must, an initial proportion of 2-6% of killer yeasts was responsible for protracted fermentation and suppression of isogenic sensitive strains. A more variable initial proportion was needed to get the same effect with non-isogenic strains. The suspended solids that remain in the must after cold-settling decreased killer toxin effect. The addition of bentonite to the must avoided protracted fermentation and the suppression of sensitive strains; however, the addition of yeast dietary nutrients with yeast cell walls did not, although it decreased fermentation lag.

Culture Media↗
PubMed1999

Importance of colonic bacterial fermentation in short bowel patients: small intestinal malabsorption of easily digestible carbohydrate.

The small intestine's large capacity for glucose absorption and for adaptation seems to contradict the reported importance of carbohydrate malabsorption in short bowel (SB) patients. The aim of the present study was to investigate the occurrence of malabsorption in these patients ingesting realistic amounts of carbohydrates. We performed a dose-response study [ingestion of increasing amounts of glucose and complex carbohydrates (boiled rice and wheat bread), and the nonabsorbable disaccharide lactulose] in SB patients with an intact colon. The hydrogen (H2) -breath test and changes in serum acetate were used to evaluate colonic fermentation and, thus, indirectly, the lack of small intestinal carbohydrate assimilation. Blood glucose and plasma insulin were measured to evaluate absorption. Plasma concentrations of the ileal brake hormones--glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY)--were measured to test whether release of these hormones was related to colonic fermentation. Significant amounts of 25 g and 50 g glucose, and of the bread and rice meals were fermented rather than absorbed, as judged by the increases in end-expiratory H2. Serum acetate concentrations were significantly higher in SB patients than in healthy controls. The orocecal transit times of all test meals ranged from 15 to 120 min. GLP-1 and PYY releases in SB patients were significantly higher than in healthy volunteers. They were mutually parallel and paralleled the increase in insulin. They were not related to ongoing fermentation or to intraluminal carbohydrate content per se, but most probably to absorption of glucose in the distal bowel. In conclusion, well-adapted SB patients had pronounced small intestinal malabsorption of carbohydrate, even after ingestion of small amounts of easily absorbable carbohydrates. A fast small intestinal spreading of carbohydrates, once in the small intestine, and a spill-over to the colon seem to explain the data best.

Adult↗
PubMed1997

Modification of colonic fermentation by bifidobacteria and pH in vitro. Impact on lactose metabolism, short-chain fatty acid, and lactate production.

Colonic fermentation plays an important role in the prevention of lactose intolerance and intestinal disorders. The objectives of this study were to evaluate whether supplementation with bifidobacteria modify colonic fermentation of lactose and short-chain fatty acid production and to assess influence of the pH in an in vitro continuous culture system. There was a significantly greater reduction in lactose concentrations at pH 6.7 than that at either pH 6.2 or pH 5.7, accompanied by the highest beta-galactosidase activity and D-lactate production. Bifidus supplementation reduced lactose and D-lactate concentrations and increased acetate production at pH 6.7. The study demonstrates that lactose is rapidly metabolized by colonic bacteria and lactose fermentation in vitro is pH dependent with a maximum rate at pH 6.7. Bifidobacteria supplementation may have the potential to improve lactose fermentation and to manipulate SCFA and lactate production.

Adult↗
PubMed2002

Loss of fermentative capacity in baker's yeast can partly be explained by reduced glucose uptake capacity.

Initial attempts to increase fermentative capacity of baker's yeast focussed on the overproduction of single enzymes, which proved to be insufficient. Nowadays many components of the system are monitored simultaneously in a search for a correlation with fermentative capacity. However, this strategy has not yet proven fruitful either. Here we investigate an element previously neglected, the glucose transporter, and find that a loss of glucose transport capacity correlates with a decrease of fermentative capacity during nutrient starvation. However the correlation is not unique, suggesting that the loss of fermentative capacity cannot be attributed to an inactivation of glucose transport alone. Our results suggest the necessity to use a detailed kinetic model as an underlying working hypothesis and to use Metabolic Control Analysis to examine the pathway's control properties.

Biological Transport↗
PubMed2002

Effect of Lactobacillus plantarum 299v on colonic fermentation and symptoms of irritable bowel syndrome.

A number of recent clinical trials have promoted the use of probiotic bacteria as a treatment for irritable bowel syndrome (IBS). The recent demonstration of abnormal colonic fermentation in some patients with this condition provides an opportunity for the objective assessment of the therapeutic value of these bacteria. This study was designed to investigate the effects of Lactobacillus plantarum 299V on colonic fermentation. We conducted a double-blind, placebo-controlled, cross-over, four-week trial of Lactobacillus plantarum 299V in 12 previously untreated patients with IBS. Symptoms were assessed daily by a validated composite score and fermentation by 24-hr indirect calorimetry in a 1.4-m3 canopy followed by breath hydrogen determination for 3 hr after 20 ml of lactulose. On placebo, the median symptom score was 8.5 [6.25-11.25 interquartile range (IQR)], the median maximum rate of gas production was 0.55 ml/min (0.4-1.1 IQR), and the median hydrogen production was 189.7 ml/24 hr (118.3-291.1 IQR). On Lactobacillus plantarum 299V the median symptom score was 8 (6.75-13.5 IQR), the median maximum rate of gas production 0.92 ml/min (0.45-1.5 IQR), and the median hydrogen production 208.2 ml/24 hr (146-350.9 IQR). There was no significant difference. Breath hydrogen excretion after lactulose was reduced by the probiotic (median at 120 min, 6 ppm; placebo, 17 ppm; P = 0.019). In conclusion, Lactobacillus plantarum 299V in this study did not appear to alter colonic fermentation or improve symptoms in patients with the irritable bowel syndrome.

Adult↗
PubMed2003

Yeasts present during spontaneous fermentation of Lake Erie Chardonnay, Pinot Gris and Riesling.

The composition of wine yeast populations, present during spontaneous fermentation of Chardonnay, Pinot Gris and Riesling from the Lake Erie Region was studied. A combination of biochemical and molecular techniques was used to identify non-Saccharomyces and Saccharomyces yeast isolates. The biochemical techniques included analysis of yeast isolates by sugar fermentation and carbon and nitrogen assimilation. Molecular techniques involved ribotyping of a highly variable segment in the 26S rRNA gene using DNA sequence analysis and restriction fragment length polymorphism of amplified DNA. The results show that of the non-Saccharomyces yeasts, several related species of Hanseniaspora, were the most abundant yeasts present during early stages of fermentation. Later in fermentation S. cerevisiae dominated, and based on biochemical analyses consisted of a heterogeneous group of genotypes. There were no major differences in yeast populations among the three types of juice analyzed.

DNA, Ribosomal↗
PubMed2003

Genetically modified soybeans: false-positive detection in fermented natural soybean (tempe).

Tempe was prepared using mixtures of natural soybean and genetically modified Roundup Ready (RUR) soybean fermented with natural Rhizopus sp. The amount of RUR soybean was quantified using an ELISA plate test. The RUR signal decreased during fermentation. In the control experiments on fermentation of non-RUR soybean, the tempe gave a false-positive RUR signal. The cross-reacting substance was generated only in non-RUR soybean during fermentation by Rhizopus sp., Rhizopus oligosporus, R. oryzae, Mucor rouxii and Aspergillus awamori.

Antigens↗
PubMed2004

Establishing a versatile fermentation and purification procedure for human proteins expressed in the yeasts Saccharomyces cerevisiae and Pichia pastoris for structural genomics.

We describe the introduction of the yeasts Saccharomyces cerevisiae and Pichia pastoris as eukaryotic hosts for the routine production of recombinant proteins for a structural genomics initiative. We have previously shown that human cDNAs can be efficiently expressed in both hosts using high throughput procedures. Expression clones derived from these screening procedures were grown in bioreactors and the over-expressed human proteins were purified, resulting in obtaining significant amounts suitable for structural analysis. We have also developed and optimized protocols enabling a high throughput, low cost fermentation and purification strategy for recombinant proteins for both S. cerevisiae and P. pastoris on a scale of 5 to 10 mg. Both batch and fed batch fermentation methods were applied to S. cerevisiae. The fed batch fermentations yielded a higher biomass production in all the strains as well as a higher productivity for some of the proteins. We carried out only fed batch fermentations on P. pastoris strains. Biomass was produced by cultivation on glycerol, followed by feeding methanol as carbon source to induce protein expression. The recombinant proteins were expressed as fusion proteins that include a N-terminal His-tag and a C-terminal Strep-tag. They were then purified by a two-step chromatographic procedure using metal-affinity chromatography and StrepTactin-affinity chromatography. This was followed by gel filtration for further purification and for buffer exchange. This three-step purification procedure is necessary to obtain highly purified proteins from yeast. The purified proteins have successfully been subjected to crystallization and biophysical analysis.

Chromatography, Affinity↗
PubMed1998

Effects of a milk product, fermented by Lactobacillus acidophilus and with fructo-oligosaccharides added, on blood lipids in male volunteers.

OBJECTIVE: To investigate in adult male volunteers the effect of a new fermented milk product, fermented by Lactobacillus acidophilus and with fructo-oligosaccharides added, on blood lipids. DESIGN: Randomized placebo-controlled double-blind two-way cross over trial with two treatment periods of three weeks, separated by a wash-out period of one week. SETTING: the study was performed at the TNO Nutrition and Food Research Institute in Zeist, The Netherlands. SUBECTS: Thirty normal healthy men, aged 33-64y (mean serum total cholesterol level: 5.23 +/- 1.03 (s.d.)), were selected for this study. Normal health was assessed by pre study screening. All subjects were used to an average Dutch food pattern. INTERVENTIONS: During the treatment periods subjects consumed three times daily a 125 ml of either test or reference product as a part of their habitual diet. The test product was a milk, fermented by yogurt starters and Lactobacillus acidophilus, and contained 2.5% fructo-oligosaccharides, 0.5% vegetable oil and 0.5% milk fat. The reference product was a traditional yogurt (milk fermented only by yogurt strains), containing 1% milk fat. Blood samples for serum lipid analysis and blood glucose measurements were taken before the start of the experiment and at the end of both treatment periods. RESULTS: As compared to the reference product, consumption of the test product resulted in significantly lower values for serum total cholesterol (P < 0.001), LDL-cholesterol (P < 0.005), and the LDL/HDL-ratio (P < 0.05) by 4.4, 5.4 and 5.3% respectively. Levels of serum HDL-cholesterol, triglycerides and blood glucose remained essentially unchanged. The beneficial effects of the test product on serum cholesterol were largely related to an increase of this parameter during the consumption of the reference product. CONCLUSIONS: As compared to traditional yogurt, daily consumption of three times 125 ml of test product specifically lowered serum LDL-cholesterol levels in normal healthy male adult subjects with borderline elevated levels of serum total cholesterol within three weeks.

Adult↗
PubMed2002

Fermented milks: a historical food with modern applications--a review.

BACKGROUND: : This paper was presented at the symposium which was organized by Instituto Danone Mexico in May 2001, and it provides an overview of the current scientific knowledge on fermented milks concerning the historical developments, manufacturing stages, classification of such products, and nutritional aspects. Particular attention has been paid to the human health benefits associated with the consumption of these products, the use of probiotic starter cultures and their industrial applications, and the significance of using a trained sensory panel for the evaluation of probiotic fermented milks made with different commercial blends of starter cultures. The paper also highlights the future research areas for the exploitation of starter microflora (Lactobacillus, Bifidobacterium and Enterococcus species) in fermented milk products. CONCLUSION: : This review indicates that the complex metabolism of the starter cultures is well established; however, more information is still needed on specific microbial metabolites such as polymerization of milk sugars for the production of exopolysaccharides and the modification of the milk peptides and secretion of bacteriocins. More clinical studies are still required to establish the 'functional' health benefits of probiotic fermented milks to humans.

Animals↗
PubMed2003

Starch fermentation by faecal bacteria of infants, toddlers and adults: importance for energy salvage.

OBJECTIVE: Little is known of the degree to which the colon salvages energy through starch fermentation in young children. Using a simulated colonic environment, we aimed to account for the fate of fermented raw and cooked starch in two groups of young children and in adults. DESIGN: A slurry was prepared from faecal samples from six infants (7-10 months), six toddlers (16-21 months) and seven adults (24-56 y). Each slurry was anaerobically incubated with raw or cooked maize starch in MacCartney bottles in a shaking water bath. Parallel incubations were stopped at 4 and 24 h. The headspace gas volume was analysed for CO(2) and methane. The culture supernatant was analysed for short-chain fatty acids (SCFA), lactate and residual starch. RESULTS: Different patterns of fermentation were seen at 4 and 24 h. For raw starch, the production of SCFA decreased with subject age at 4 h but not at 24 h. With both substrates at 4 h, toddler stools produced significantly more CO(2) than infants or adults, but there were no statistical differences at 24 h. Methane was detected in three adults only. Lactate was detected mainly at 4 h in children. CONCLUSIONS: The results suggest that fermentation, particularly of raw starch, is a more rapid process in young children than in adults. A highly efficient energy salvage process may occur in the colon of young children.

Adult↗
PubMed2006

Urinary excretion of equol by postmenopausal women consuming soymilk fermented by probiotic bifidobacteria.

OBJECTIVE: To study the effects of consuming isoflavone aglycone-enriched soymilk fermented by bifidobacteria on urinary excretion of equol with respect to fermentation, daidzein dose, supplementation duration and background diet. DESIGN: Double-blind crossover pilot study comprising three 14-day supplementation periods separated by a washout. SETTING: Victoria University, Melbourne, Australia. SUBJECTS: Sixteen postmenopausal women. INTERVENTION: SUBJECTS randomized into two groups consuming either fermented (FS) or non-fermented soymilk (NFS), ingested three daily dosages of daidzein via soymilk and collected pooled urine specimens. Daidzein and equol were quantified using high-performance liquid chromatography. RESULTS: After 14-days supplementation six women (38%) excreted equol (>1 micromol equol/day), including four from the FS group, two of whom were classified as non-producers at day 4. Bifidobacteria ingestion, composition of daidzein and its glucosides, and carbohydrate intake appeared to influence equol formation among equol producers. CONCLUSIONS: Pilot-study group mean urinary equol excretion results provided insufficient evidence (P>0.05) that FS consumption instigates equol production in women predetermined as non-producers.

Bifidobacterium↗
PubMed2002

Thermogenesis associated with fermentable carbohydrate in humans, validity of indirect calorimetry, and implications of dietary thermogenesis for energy requirements, food energy and body weight.

BACKGROUND: Animal studies and theory show fermentable carbohydrate (FC) intake causes appreciably thermogenesis, but a similar occurrence in humans is controversial. HYPOTHESES: (a) That indirect calorimetry (IDC) is a valid method to assess thermogenesis during fermentation. (b) That a consistent and rigorous approach to the analysis of published IDC data from human studies will establish a representative thermogenic response to FC. (c) That conventional estimates of food energy and energy requirements can mismatch appreciably, more especially when thermogenesis is ignored. PURPOSE: To derive information and understanding of IDC, thermogenesis and energy balance in relation to food energy and energy requirement estimates. METHODS: (a) The validities of IDC equations that estimate the heat of reaction and carbohydrate utilization were assessed for various types of FCs under various circumstances. (b) Pooled analysis of eight published randomized cross-over studies in humans with elevation of FC intake. Studies were analysed for the first time or reanalysed according to a consistent approach with appropriate corrections for confounders. (c) Some 1500 regular and 'special' diet compositions were examined to assess the extent to which Atwater general food energy factors and updated estimates of energy requirements mismatch due to variation in substrate-associated thermogenesis and substrate-associated faecal+urinary energy losses. Impact of such mismatches on BMI was assessed under conditions of all else being equal. RESULTS: (a) Indirect calorimetry was valid, providing robust estimates of heat production during various types of fermentation; only small correction factors were necessary. By contrast, IDC equations for carbohydrate utilization sometimes applied poorly to FC. (b) A best estimate of thermogenesis in humans due to fermentation, above that due to oral glucose as a reference standard, was 0.39 (s.e.m. 0.14) kJ per kJ net metabolizable energy (NME; P<0.05, n=8 studies, total 72 humans) compared with 0.34 kJ/kJ from theory. Six sources of bias were identified; all had potential to underestimate FC thermogenesis. (c) Mismatches in energy availability and requirement estimates were often marked and translated into long-term differences in body mass index from approximately 20 to 33 kg/m(2) in average-height middle-aged initially obese women, and from approximately 22 to a non-survivable 13 kg/m(2) in initially slim women. CONCLUSIONS: (a) Indirect calorimetry is valid for the present purpose. (b) Thermogenesis in response to FC is real in humans and is comparable to that in animals and in theory. (c) Mismatches between estimates of energy requirements and dietary energy as metabolizable energy means the two expressions are not directly comparable, which has implications for the expression of food energy, energy requirements and the conduct and interpretation of research related to body weight.

Body Weight↗
PubMed2001

Protease A activity and nitrogen fractions released during alcoholic fermentation and autolysis in enological conditions.

Determination of protease A activity during alcoholic fermentation of a synthetic must (pH 3.5 at 25 degrees C) and during autolysis showed that a sixfold induction of protease A activity occurred after sugar exhaustion, well before 100% cell death occurred. A decrease in protease A activity was observed when yeast cell autolysis started. Extracellular protease A activity was detected late in the autolysis process, which suggests that protease A is not easily released. Evolution of amino acids and peptides was determined during alcoholic fermentation and during autolysis. Amino acids were released in early stationary phase. These amino acids were subsequently assimilated during the fermentation. The same pattern was observed for peptides; this has never been reported previously. During autolysis, the concentration of amino acids and peptides increased to reach a maximum of 20 and 40 mg N l(-1), respectively. This study supports the idea that although protease A activity seemed to be responsible for peptides release, there is no clear correlation among protease A activity, cell death, and autolysis. The amino acid composition of the peptides showed some variations between peptides released during alcoholic fermentation and during autolysis. Depending on aging time on yeast lees, the nature of the peptides present in the medium changed, which could lead to different organoleptic properties.

Alcohols↗
PubMed2002

Optimization of fed-batch fermentation for xylitol production by Candida tropicalis.

Xylitol, a functional sweetener, was produced from xylose by biological conversion using Candida tropicalis ATCC 13803. Based on a two-substrate fermentation using glucose for cell growth and xylose for xylitol production, fed-batch fermentations were undertaken to increase the final xylitol concentration. The effects of xylose and xylitol on xylitol production rate were studied to determine the optimum concentrations for fed-batch fermentation. Xylose concentration in the medium (100 g l(-1)) and less than 200 g l(-1) total xylose plus xylitol concentration were determined as optimum for maximum xylitol production rate and xylitol yield. Increasing the concentrations of xylose and xylitol decreased the rate and yield of xylitol production and the specific cell growth rate, probably because of an increase in osmotic stress that would interfere with xylose transport, xylitol flux to secretion to cell metabolism. The feeding rate of xylose solution during the fed-batch mode of operation was determined by using the mass balance equations and kinetic parameters involved in the equations in order to increase final xylitol concentration without affecting xylitol and productivity. The optimized fed-batch fermentation resulted in 187 g l(-1) xylitol concentration, 0.75 g xylitol g xylose(-1) xylitol yield and 3.9 g xylitol l(-1) h(-1) volumetric productivity.

Bioreactors↗
PubMed2002

Stability and activity of specific antibodies against Streptococcus mutans and Streptococcus sobrinus in bovine milk fermented with Lactobacillus rhamnosus strain GG or treated at ultra-high temperature.

Passive local immunization against dental caries is a promising approach to its prevention, as clinical evidence of active oral or nasal immunization is still limited and controversial. By means of systemic immunization of pregnant cows with a multivalent vaccine, high titres of IgG antibodies against human cariogenic bacteria, Streptococcus mutans and Streptococcus sobrinus, were produced in bovine colostrum. The purified immune product (IP) of this preparation has a number of anticariogenic properties, such as inhibition of streptococcal adherence to saliva-coated hydroxyapatite and inhibition of glucosyltransferase enzymes. This study investigated whether IP antibodies remained active and functional when added to ultra-high temperature (UHT)-treated milk or to Lactobacillus rhamnosus GG (LGG)-fermented milk stored for an extended time. LGG was chosen because of its widely known health benefits in humans and animals. A commercial UHT toddler's milk was supplemented with IP and stored for 2 months at 5, 21 and 30 degrees C. The antistreptococcal titres in UHT milk did not decline at any temperature during storage, and UHT-IP inhibited the adherence of S. mutans for up to 2 months. This was not the case with UHT toddler's milk without IgG antibodies. Milk was fermented with live LGG cells in the presence or absence of 5% IP. The antistreptococcal titres declined to about 30% of the original titres after storage. Fresh milk alone slightly enhanced streptococcal adhesion but fresh milk with IP inhibited the adherence of S. mutans by over 50%. LGG-positive fermented milk without antibodies also inhibited (P < 0.05) the adhesion by about 40%. In both LGG-fermented and UHT immune milk, the activity of antibodies against cariogenic streptococci was maintained during the expected shelf-life of these products. From the anticariogenic point of view it may be beneficial to add bovine-specific antibodies against mutans streptococci to probiotic LGG-containing milk products.

Animals↗
PubMed1999

Stable expression of the Lactobacillus casei bacteriophage A2 repressor blocks phage propagation during milk fermentation.

A general strategy was applied to implement resistance against temperate bacteriophages that infect food fermentation starters through cloning and expression of the phage repressor. Lactobacillus casei ATCC 393 and phage A2 were used to demonstrate its feasibility as milk fermentation is drastically inhibited when the strain is infected by this phage. The engineered strain Lact. casei EM40::cI, which has the A2 repressor gene (cI) integrated into the genome, was completely resistant and able to ferment milk whether phage was present or not. In addition, viable phages were eliminated from the milk, probably through adsorption to the cell wall. Finally, the integration of cI in the genome resulted in a stable resistance phenotype, being unnecessary selective pressure during milk fermentation.

Animals↗
PubMed1999

Sorbitol-fermenting bifidobacteria as indicators of diffuse human faecal pollution in estuarine watersheds.

Sorbitol fermenting bifidobacteria were evaluated as indicators of non-point source human faecal pollution to three sub-estuaries with elevated faecal coliform densities. Human-specific bifidobacteria correlated with identifiable human sanitary deficiencies in feeder streams to estuarine creeks in two of three watersheds examined, one rural and one moderately developed. Sorbitol-fermenting bifidobacteria were recovered at densities ranging from 1 to 90 colony-forming-units 100 ml-1 in 11 of 258 water samples but were undetected in sediment (n = 68) and scat from resident wildlife (deer, muskrat and raccoon, n = 20). Failure to detect sorbitol-fermenting bifidobacteria in water samples during the summer months was consistent with laboratory microcosm results showing non-recoverability of Bifidobacterium adolescentis after 5-9 d in membrane-filtered estuarine water at 23 and 30 degrees C, but persistence for 4 weeks at 10 degrees C. Persistence of sewage-derived bifidobacteria in membrane-filtered freshwater at 15 degrees C was also observed. Recovery of sorbitol-fermenting bifidobacteria was complicated by high background levels of Gram-positive rods and cocci. Use of propionic acid and reduced pH (pH = 5.0), or use of a two-step resuscitation protocol using non-selective and selective media, did not improve recovery. Although human specific bifidobacteria hold promise as indicators of diffuse faecal contamination, methodological constraints now limit its application to situations of gross contamination, or sampling potential sources during environmental conditions conducive to bifid persistence.

Animals↗