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PubMed1993

Effects of pH, potassium, magnesium, and bacterial growth phase on lysozyme inhibition of glucose fermentation by Streptococcus mutans 10449.

The effects of physiological (saliva and plaque fluid) concentrations of potassium and magnesium and growth phase on lysozyme inhibition of glucose fermentation by S. mutans 10449 were investigated. Glucose fermentations were carried out in a pH-stat at pH 7.0 or 5.5. Cells were at least two times more sensitive to lysozyme in the early-to-middle exponential phase compared with the stationary phase. S. sobrinus 6715 exhibited three-fold greater lysozyme resistance than S. rattus BHT or S. mutans 10449. The concentration of potassium which reduced lysozyme inhibition of S. mutans 10449 fermentation by 50% was 0.2 and 10 mmol/L for stationary and exponential phase cells, respectively. Corresponding values for magnesium were < or = 0.01 and 0.50 mmol/L. Potassium and magnesium exhibited little pH dependence in their reduction of lysozyme inhibition of fermentation by exponential- or stationary-phase S. mutans 10449. The results suggest that: (i) lysozyme interaction with stationary-phase cells involves more non-inhibitory modes than with exponential-phase cells, and (ii) lysozyme may be more effective as an antibacterial agent in saliva than in plaque fluid.

Analysis of Variance↗
PubMedDate not supplied

Dietary fiber and total enteral nutrition: fermentative assessment of five fiber supplements.

Total enteral nutrition (TEN) formulas supplemented with dietary fiber, typically soy polysaccharide, are in widespread clinical use. Five commercially available dietary fiber supplements obtained from fruits (apple, grapefruit, orange, prune, tomato) were examined for potential use in TEN formulas. In vitro fermentations of 0, 4, 8, 12, and 24 hours' duration with human fecal microbiota from three different donors were conducted to assess colonic fermentative effects. Short-chain fatty acid and hydrogen productions differed significantly with fiber source. The most rapid fermentation rate was with tomato followed by orange, grapefruit, apple, and finally prune fiber. Such differences in fermentability should be considered when fiber sources are selected to supplement TEN formulas.

Dietary Fiber↗
PubMedDate not supplied

Short-chain fatty acids, lactate, and ammonia in ileorectal and ileal pouch contents: a model of cecal fermentation.

Fecal concentrations of total short-chain fatty acids were normal in 16 patients with ileorectal anastomoses (mean +/- SEM, 99.7 +/- 10.3 mmol/L) and 28 patients with ileal pouch-anal anastomoses (138.8 +/- 8.5 mmol/L) and did not differ from those in 14 healthy noncolectomized controls (130.7 +/- 12.6 mmol/L). Acetate:propionate:butyrate:isobutyrate+valerate+isovalerate ratios were similar in the ileorectum (71:12:12:5%) and in the colorectum (66:14:13:7%) of healthy noncolectomized controls, whereas the concentration of acetate was increased at the expense of the polypeptide-derived isobutyrate, valerate, and isovalerate in the ileal pouch (77:12:11:1%). Ammonia was accordingly significantly diminished in ileal pouch contents (28.8 +/- 3.2 mmol/L vs 45.2 +/- 4.1 mmol/L in controls) in contrast to concentrations in ileorectal contents (36.2 +/- 5.3 mmol/L). Concentrations of lactate were normal and low. Twenty-four-hour productions of total short-chain fatty acids in 16.6% fecal homogenates from both groups of patients were normal. Addition of saccharides (eg, glucose, starch, pectin, ispaghula husk) increased the production of acetate, propionate, and butyrate and decreased the production of ammonia and isobutyrate, valerate, and isovalerate, which was increased in homogenates with albumin added. This pattern of substrate fermentation was similar in homogenates from ileal pouch, ileorectum, and control colorectum. In conclusion, the concentrations of short-chain fatty acids, lactate, and ammonia indicate that ileorectal fermentation resembles normal colorectal fermentation in noncolectomized healthy individuals, whereas the fermentation in ileal pouch contents seems to be more carbohydrate predominated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Effect of fiber and its fermentation on colonic adaptation after cecal resection in the rat.

BACKGROUND: The role of fiber in postresection adaptation is poorly understood. We examined the significance of short-chain fatty acids produced by intracolonic fiber fermentation during colonic adaptation. METHODS: Rats underwent one of three surgeries: control laparotomy, cecal resection, or cecal resection with placement of perfusion catheter. Rats of each surgical group were randomly assigned to receive treatment regimens of standard fiber diet (with or without fermentation-suppressing antibiotics), fiber-free diet, or diet plus intracolonic perfusion of short-chain fatty acids. Adaptation parameters of mucosal weight, mucosal DNA and protein content, water absorption, and butyrate absorption were measured. RESULTS: Compared with controls, postresection rats that were fed fiber had 65% greater basal and 112% greater butyrate-stimulated water absorption as well as 140% greater butyrate absorption. Fiber-fed rats exhibited significantly greater colonic weight and colonic mucosal protein after cecal resection. These changes were absent in postresection rats fed a fiber-free diet. Inhibition of fermentation by neomycin and metronidazole added to a standard fiber diet also prevented postresection adaptation. All adaptive changes were restored when the cecal-resection rats that were fed the fiber diet with antibiotics received an intracolonic infusion of short-chain fatty acids. Adaptation did not occur when short-chain fatty acids were infused into colons of postresection rats that were fed a fiber-free diet. CONCLUSIONS: Cecal resection leads to significant functional and structural changes in the adapting residual colon. Fermentation of dietary fiber by colonic flora to short-chain fatty acids is necessary, but it alone is not sufficient to mediate adaptation.

Adaptation, Physiological↗
PubMed1999

New 6-O-acyl isoflavone glycosides from soybeans fermented with Bacillus subtilis (natto). I. 6-O-succinylated isoflavone glycosides and their preventive effects on bone loss in ovariectomized rats fed a calcium-deficient diet.

Three new 6-O-acylated isoflavone glycosides were isolated from soybeans fermented with Bacillus subtilis (natto) and identified as daidzein 7-O-beta-(6''-O-succinyl)-D-glucoside (1), genistein 7-O-beta-(6''-O-succinyl)-D-glucoside (2), and glycitein 7-O-beta-(6''-O-succinyl)-D-glucoside (3) on the basis of spectral data and chemical transformations. During fermentation, the content of the isoflavone glycosides first decreased and then increased, whereas the corresponding 6''-O-succinyl derivatives first accumulated and then decreased, in either soybeans or soybean cooking solution. These changes suggest that enzymatic interconversion of isoflavone glycosides and the corresponding 6''-O-succinylated derivatives occurs in these media during fermentation. The 6-O-succinylated isoflavone glycosides 1, 2 and 3 accounted for 4.8, 7.2 and 0.6%, respectively, of the total isoflavones in commercial fermented soybeans (Japanese natto). Oral administration of 1 or 2 alone for 4 weeks at a dose of 50 mg/kg/d prevented bone loss in ovariectomized (ovx) rats fed a calcium-deficient diet, being as effective as the positive controls, daidzin and genistin, respectively. Compound 1 seems to be proestrogenic, like daidzin, which suppresses bone resorption to prevent bone loss after ovariectomy by directly acting on bone sites, while 2 appears to have a different mechanism of action, like that of genistin.

Animals↗
PubMed2005

Functional effects of Japanese style fermented soy sauce (shoyu) and its components.

The functional effects of Japanese style fermented soy sauce (shoyu) have been studied. Soy sauce promotes digestion, because the consumption of a cup of clear soup containing soy sauce enhances gastric juice secretion in humans. Soy sauce possesses antimicrobial activity against bacteria such as Staphylococcus aureus, Shigella flexneri, Vibrio cholera, Salmonella enteritidis, nonpathogenic Escherichia coli and pathogenic E. coli O157:H7. Soy sauce also contains an antihypertensive component. An angiotensin I-converting enzyme inhibitor having antihypertensive effects was found in soy sauce. The active compound was identified as nicotianamine, which comes from soybeans. Soy sauce exhibits anticarcinogenic effects. Giving diets containing soy sauce to mice inhibit benzo[a]pyrene (BP)-induced forestomach neoplasia. The anticarcinogenic compounds in soy sauce were identified. The flavor components of Japanese style fermented soy sauce, such as 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF), which is a characteristic flavor component of Japanese style fermented soy sauce and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 4-hydroxy-5-methyl-3(2H)-furanone (HMF) exhibit antioxidant activities and anticarcinogenic effects on BP-induced mice forestomach neoplasia when fed following carcinogen exposure. The feeding of a diet containing 10% soy sauce to male C3H mice for 13 months also reduces the frequency and multiplicity of spontaneous liver tumors. HDMF and HEMF also exhibit anticataract effects in the spontaneous cataract rat (ICR/f rat). Fermented soy sauce contains three tartaric isoflavone derivatives called shoyuflavones. These shoyuflavones were shown to have inhibitory activities against histidine decarboxylase, which produces histamine, a mediator of inflammation, allergy and gastric acid secretion. Soy sauce also exhibits antiplatelet activity. beta-Carbolines were isolated from soy sauce as the active compounds. Soybeans and wheat, which are the main raw materials of soy sauce, are allergenic foods. However, recent studies by enzyme-linked immunosorbent assay showed the absence of soybean and wheat allergens in soy sauce.

Animals↗
PubMed1994

Fermentative production of tryptophan by a stable recombinant strain of Corynebacterium glutamicum with a modified serine-biosynthetic pathway.

Introduction of plasmid pKW99, which coexpresses the deregulated 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase and tryptophan-biosynthetic enzymes, into tryptophan-producing Corynebacterium glutamicum KY10894 resulted in a marked increase (54%) in yield of tryptophan production (43 g/liter), but incurred two problems. One was a decline in sugar consumption at the late stage of fermentation, and the other the loss of the plasmid in the absence of selective pressure. The retarded sugar assimilation was found to be attributed to the death of cells that arose from the detrimental action of indole, the last intermediate in the tryptophan pathway, accumulated as a by-product. A chain of these events simultaneously disappeared when serine, the other substrate of the final reaction by tryptophan synthase, was added. These results indicated that a limiting supply of serine was the cause of the decline in the sugar consumption. Thus, to increase carbon flux into serine, the gene for 3-phosphoglycerate dehydrogenase (PGD), the first enzyme in the serine pathway, was cloned from wild-type C. glutamicum ATCC 31833 and joined onto pKW99 to generate pKW9901. Strain KY10894 transformed with pKW9901 favorably consumed sugar through fermentation with accumulating little indole. Furthermore, on the basis of the observation that serine in the medium was consumed rapidly by the recombinant cells, we developed a unique plasmid stabilization system composed of KY9218 (a PGD-deficient serine-requiring strain of KY10894) and pKW9901: In its combination, cells lacking the plasmid should not proliferate in the fermentation medium which does not contain serine. Even if selective pressure was not applied, the modified strain KY9218 with pKW9901 stably maintained the plasmid during fermentation and produced 50 g/liter of tryptophan in a 61% increased yield relative to strain KY10894.

Carbohydrate Dehydrogenases↗
PubMed2001

Appearance of poor-fermenting variants in brewing yeast culture.

A class of yeast variants appears after cultivation of a bottom-fermenting brewing yeast strain, IFO2003. Although IFO2003 fails to grow well above 33 degrees C, the variants can grow up to 34 degrees C. Temperature-resistance and an acquired phenotype of maltose poor-fermentation ability are strictly correlated in the bottom-fermenting brewing yeast, enabling us to develop easy estimation of the fermentation ability of the variants.

Colony Count, Microbial↗
PubMed2002

Optimization of glycerol fed-batch fermentation in different reactor states: a variable kinetic parameter approach.

To optimize the fed-batch processes of glycerol fermentation in different reactor states, typical bioreactors including 500-mL shaking flask, 600-mL and 15-L airlift loop reactor, and 5-L stirred vessel were investigated. It was found that by reestimating the values of only two variable kinetic parameters associated with physical transport phenomena in a reactor, the macrokinetic model of glycerol fermentation proposed in previous work could describe well the batch processes in different reactor states. This variable kinetic parameter (VKP) approach was further applied to model-based optimization of discrete-pulse feed (DPF) strategies of both glucose and corn steep slurry for glycerol fed-batch fermentation. The experimental results showed that, compared with the feed strategies determined just by limited experimental optimization in previous work, the DPF strategies with VKPs adjusted could improve glycerol productivity at least by 27% in the scale-down and scale-up reactor states. The approach proposed appeared promising for further modeling and optimization of glycerol fermentation or the similar bioprocesses in larger scales.

Bioreactors↗
PubMed2002

Scale-up of microbubble dispersion generator for aerobic fermentation.

A laboratory-scale microbubble dispersion (MBD) generator was shown to improve oxygen transfer to aerobic microorganisms when coupled to the conventional air-sparger. However, the process was not demonstrated on a large scale to prove its practical application. We investigated the scale-up of a spinning-disk MBD generator for the aerobic fermentation of Saccharomyces cerevisiae (baker's yeast). A 1-L spinning-disk MBD generator was used to supply air for 1- and 50-L working volume fermentation of baker's yeast. For the two levels investigated, the MBD generator maintained an adequate supply of surfactant-stabilized air microbubbles to the microorganisms at a relatively low agitation rate (150 rpm). There was a significant improvement in oxygen transfer to the microorganism relative to the conventional sparger. The volumetric mass transfer coefficient, kLa, for the MBD system at 150 rpm was 765 h(-1) compared to 937 h(-1) for the conventional sparger at 500 rpm. It is plausible to surmise that fermentation using larger working volumes may further improve the kLa values and the dissolved oxygen (DO) levels because of longer hold-up times and, consequently, improve cell growth. There was no statistically significant difference between the cell mass yield on substrate (0.43 g/g) under the MBD regime at an agitation rate of 150 rpm and that achieved for the conventional air-sparged system (0.53 g/g) at an agitation rate of 500 rpm. The total power consumption per unit volume of broth in the 50-L conventional air-sparged system was threefold that for the MBD unit for a similar product yield. Practical application of the MBD technology can be expected to reduce power consumption and therefore operating costs for aerobic fermentation.

Aerobiosis↗
PubMedDate not supplied

Fermentation diagnosis by multivariate statistical analysis.

During the course of fermentation, online measuring procedures able to estimate the performance of the current operation are highly desired. Unfortunately, the poor mechanistic understanding of most biologic systems hampers attempts at direct online evaluation of the bioprocess, which is further complicated by the lack of appropriate online sensors and the long lag time associated with offline assays. Quite often available data lack sufficient detail to be directly used, and after a cursory evaluation are stored away. However, these historic databases of process measurements may still retain some useful information. A multivariate statistical procedure has been applied for analyzing the measurement profiles acquired during the monitoring of several fed-batch fermentations for the production of erythromycin. Multivariate principal component analysis has been used to extract information from the multivariate historic database by projecting the process variables onto a low-dimensional space defined by the principal components. Thus, each fermentation is identified by a temporal profile in the principal component plane. The projections represent monitoring charts, consistent with the concept of statistical process control, which are useful for tracking the progress of each fermentation batch and identifying anomalous behaviors (process diagnosis and fault detection).

Biotechnology↗
PubMedDate not supplied

Gibberellic acid production by solid-state fermentation in coffee husk.

Five strains of Gibberella fujikuroi and one of Fusarium moniliforme were screened for the production of gibberellic acid (GA3) in coffee husk, and based on the results, one strain, G. fujikuroi LPB-06, was selected. The comparative production of GA3 by solid-state fermentation and submerged fermentation indicated better productivity with the former technique, mainly with pretreated substrate. The GA3 accumulation was 6.1 times higher in the case of solid-state fermentation. Considering the C:N relation, higher yields of GA3 were achieved using a mixed substrate comprising coffee husk and cassava bagasse (7:3, dry wt), increasing the results twice. Supplementation of an optimized saline solution containing 0.03% FeSO4 and 0.01% (NH4)2SO4 enhanced the accumulation of GA3 1.7 times in the fermented substrate. Under the finally optimized condition, the culture gave a maximum of 492.5 mg of GA3/kg of dry substrate, with a pH of 5.3, moisture of 75%, and incubation temperature of 29 degrees C. GA3 yield was almost 13 times more than the initial results.

Chromatography, High Pressure Liquid↗
PubMed2003

Effect of lignocellulosic degradation compounds from steam explosion pretreatment on ethanol fermentation by thermotolerant yeast Kluyveromyces marxianus.

The filtrate from steam-pretreated poplar was analyzed to identify degradation compounds. The effect of selected compounds on growth and ethanolic fermentation of the thermotolerant yeast strain Kluyveromyces marxianus CECT 10875 was tested. Several fermentations on glucose medium, containing individual inhibitory compounds found in the hydrolysate, were carried out. The degree of inhibition on yeast strain growth and ethanolic fermentation was determined. At concentrations found in the prehy-drolysate, none of the individual compounds significantly affected the fermentation. For all tested compounds, growth was inhibited to a lesser extent than ethanol production. Lower concentrations of catechol (0.96 g/L) and 4-hydroxybenzaldehyde (1.02 g/L) were required to produce the 50% reduction in cell mass in comparison to other tested compounds.

Benzaldehydes↗
PubMedDate not supplied

Fermentative production of curdlan.

Curdlan was produced by pure culture fermentation using Agrobacterium radiobacter NCIM 2443. Three different carbon sources (glucose, sucrose, maltose) were selected for study. Sucrose was found to be the most efficient. Utilization of sugar during the course of fermentation was studied, and the data were correlated to the production of curdlan. Curdlan mimics a secondary metabolite, in that its synthesis is associated with the poststationary growth phase of nitrogen-depleted batch culture. This was inferred from the results obtained from utilization of nitrogen. Regulation of pH at 6.1 +/- 0.3 resulted in an increased yield of curdlan from 2.48 to 4.8 g/L, and the corresponding increase in succinoglucan production was from 1.78 to 2.8 g/L. An attempt was made to increase curdlan production by the addition of the uridine nucleotides UMP and UDP-glucose to the fermentation broth. It was found that UDP-glucose at 0.8 microg/mL and UMP at 0.6 microg/mL served as precursors for curdlan and succinoglucan production when added after 18 h of nitrogen depletion in the fermentation broth.

Fermentation↗
PubMed2006

Separate and simultaneous enzymatic hydrolysis and fermentation of wheat hemicellulose with recombinant xylose utilizing Saccharomyces cerevisiae.

Fermentations with three different xylose-utilizing recombinant Saccharomyces cerevisiae strains (F12, CR4, and CB4) were performed using two different wheat hemicellulose substrates, unfermented starch free fibers, and an industrial ethanol fermentation residue, vinasse. With CR4 and F12, the maximum ethanol concentrations obtained were 4.3 and 4 g/L, respectively, but F12 converted xylose 15% faster than CR4 during the first 24 h. The comparison of separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) with F12 showed that the highest, maximum ethanol concentrations were obtained with SSF In general, the volumetric ethanol productivity was initially, highest in the SHF, but the overall volumetric ethanol productivity ended up being maximal in the SSF, at 0.013 and 0.010 g/Lh, with starch free fibers and vinasse, respectively.

Catalase↗
PubMed2000

Fermentations of pectin-rich biomass with recombinant bacteria to produce fuel ethanol.

Pectin-rich residues from sugar beet processing contain significant carbohydrates and insignificant amounts of lignin. Beet pulp was evaluated for conversion to ethanol using recombinant bacteria as biocatalysts. Hydrolysis of pectin-rich residues followed by ethanolic fermentations by yeasts has not been productive because galacturonic acid and arabinose are not fermentable to ethanol by these organisms. The three recombinant bacteria evaluated in this study, Escherichia coli strain KO11, Klebsiella oxytoca strain P2, and Erwinia chrysanthemi EC 16 pLOI 555, ferment carbohydrates in beet pulp with varying efficiencies. E. coli KO11 is able to convert pure galacturonic acid to ethanol with minimal acetate production. Using an enzyme loading of 10.5 filter paper units of cellulase, 120.4 polygalacturonase units of pectinase, and 6.4 g of cellobiase (per gram of dry wt sugar beet pulp), with substrate addition after 24 h of fermentation, 40 g of ethanol/L was produced. Other recombinants exhibited lower ethanol yields with increases in acetate and succinate production.

Alcohol Dehydrogenase↗
PubMed2001

Fermentation performance assessment of a genomically integrated xylose-utilizing recombinant of Zymomonas mobilis 39676.

In pH-controlled batch fermentations with pure sugar synthetic hardwood hemicellulose (1% [w/v] glucose and 4% xylose) and corn stover hydrolysate (8% glucose and 3.5% xylose) lacking acetic acid, the xylose-utilizing, tetracycline (Tc)-sensitive, genomically integrated variant of Zymomonas mobilis ATCC 39676 (designated strain C25) exhibited growth and fermentation performance that was inferior to National Renewable Energy Laboratory's first-generation, Tc-resistant, plasmid-bearing Zymomonas recombinants. With C25, xylose fermentation following glucose exhaustion was markedly slower, and the ethanol yield (based on sugars consumed) was lower, owing primarily to an increase in lactic acid formation. There was an apparent increased sensitivity to acetic acid inhibition with C25 compared with recombinants 39676:pZB4L, CP4:pZB5, and ZM4:pZB5. However, strain C25 performed well in continuous fermentation with nutrient-rich synthetic corn stover medium over the dilution range 0.03-0.06/h, with a maximum process ethanol yield at D = 0.03/h of 0.46 g/g and a maximum ethanol productivity of 3 g/(L x h). With 0.35% (w/v) acetic acid in the medium, the process yield at D = 0.04/h dropped to 0.32 g/g, and the maximum productivity decreased by 50% to 1.5 g/(L x h). Under the same operating conditions, rec Zm ZM4:pZB5 performed better; however, the medium contained 20 mg/L of Tc to constantly maintain selective pressure. The absence of any need for antibiotics and antibiotic resistance genes makes the chromosomal integrant C25 more compatible with current regulatory specifications for biocatalysts in large-scale commercial operations.

Acetic Acid↗
PubMed2001

Modeling of saccharide utilization in primary beer fermentation with yeasts immobilized in calcium alginate.

Immobilized beer fermentation was studied using an industrial bottom-fermenting yeast strain Saccharomyces cerevisiae. The yeast cells were immobilized in 2.5% calcium alginate gel and used for brewing in a five-vessel cascade reactor. The fermentation was performed at 15 degrees C at various flow rates. A nonstructured mathematical model was developed to simulate the performance of continuous primary fermentation of lager beer. The model was based on the following variables: maltose, maltotriose, glucose, fructose, ethanol, and cell concentration. Experimental values of these variables were determined in samples taken at regular intervals. For experimental data fitting a nonlinear regression was used. Substrate consumption was characterized by specific substrate consumption rate and saturation constant. The values of these two parameters were optimized for all four substrates. Inhibition effects of substrates and product were analyzed using various inhibition patterns. Only the inhibition effect of maltose on maltose consumption was clearly identified. A good-fitting relationship for maltose inhibition was found, and inhibition constants were calculated.

Alginates↗