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PubMed1981

[Effect of cimetidine on lactose activity in patients with duodenal ulcer].

A significant decrease of the lactose levels (p less than .001) and of the glucose peaks after an overcharge of lactose (p less than .01) were found in 10 patients with duodenal ulcer after a treatment of 35 days with 1,2 daily grams of Cimetidine, when they were compared with a group treated with placebos. Also, a significant increase of the diarrhea associated with the overcharge of lactose (p less than .005) was obtained. The relation between the increase of the pH and the decrease of the lactose values was significant (r = 0,44 - p less than .01).

Cimetidine↗

PubMed1995

[Lactose digestion by milk fermented with Lactobacillus acidophilus and Lactobacillus casei of human origin].

The aim of the present study was to determine whether a fermented milk containing Lactobacillus casei and Lactobacillus acidophilus strains isolated from human subjects (CFM) and developed by CERELA (Centro de referencia para Lactobacilos) is better tolerated than regular milk (RM) by subjects with lactase deficiency (< 1 unidad) and lactose intolerance. We studied the digestion of the lactose present in the two milk preparations which were administered to 18 healthy subjects with lactase deficiency and 12 control subjects. Each subject ingested in random sequence on different days, 480 ml CFM, 480 ml RM and 240 ml CFM and 240 ml RM. Breath hydrogen (H2) test was used to measure lactose absorption and orocecal transit time (OCTT). The peak H2 ppm results after 480 ml of CFM were ingested, reached 19.5 +/- 12.1 ppm. The same reading when 480 ml of RM were ingested was 52.6 +/- 31.9 ppm (p < 0.008). The results also showed that 480 ml of CFM delayed OCTT median 111.0 +/- 6.78 min versus 54.0 +/- 5.09 min of RM (p < 0.001) and reduced the development of symptoms (p < 0.08) such as bloating (p < 0.05), borborygmi (p < 0.025) diarrhea (p < 0.05) and abdominal colics (p < 0.05). In spite of the small number of cases studied, it seems justified to conclude that CERELA fermented milk significantly influences lactose digestion and minor development of symptoms in lactase-deficient subjects and lengthens significantly the orocecal transit time compared with regular milk.

Adult↗

PubMed1995

[Significance of lactose breath test in the newborn].

Lactose breath test have been performed in healthy newborns, in whom breath hydrogen excretion was preliminarily demonstrated by lactulose breath test. 27.5% of newborns showed positive lactose breath test, with no differences related to sex and gestational age, while a higher percentage of positive test has been found in < 2500 g and formula-fed neonates compared, respectively, to > or = 2500 g and breast-fed ones. In healthy newborns, without any clinical signs of lactose intolerance, it is possible to demonstrate hydrogen in expired air; this is not equivalent of lactose malabsorption, but, instead, depends on the phenomenon of colonic fermentation that allows energy and nutrient absorption.

Breath Tests↗

PubMed1982

Cancer chemotherapy-induced lactose malabsorption in children.

To determine whether lactose malabsorption can be induced in children receiving cancer chemotherapy, lactose breath hydrogen tests (LBHT) were performed on 27 patients (ages 2 months to 16 10/12 years, mean 4 3/12 years) with neoplastic disease. Nine patients had an LBHT before their first course of chemotherapy and then 7--26 days afterwards. Eighteen other patients, less than 5 years old and presumed by virtue of age to be normal lactose absorbers, had an LBHT 7--24 days after their last course of chemotherapy. All nine in the first group had a normal LBHT before chemotherapy, and three had an abnormal LBHT 7--21 days later. Six of eighteen patients in the second group had an abnormal LBHT. Of the nine patients with an abnormal LBHT, six had a history of diarrhea associated with chemotherapy. These findings have important implications for children receiving cancer chemotherapy. High-calorie, milk-containing solutions used in nutritional support may precipitate cramps and diarrhea in some of these patients. A therapeutic trial of a low lactose diet in children in whom diarrhea develops during chemotherapy may be indicated.

Adolescent↗

PubMed2002

Measurement of glucose, sucrose and lactose in food samples with enzyme-immobilised packed-bed column reactors integrated to an amperometric enzyme electrode.

An amperometric enzyme electrode integrated with packed-bed column reactors containing immobilised enzymes was improved to measure glucose, sucrose and lactose content of food samples with only one sampling. Performance parameters of the system were investigated on the bases of linearity, sensitivity and response time. Those values were found to be 20 mM, 24.9 nA/mM and 20 s for glucose; 20 mM, 12.0 nA/mM and 3 min for sucrose; 12 mM, 10.8 nA/mM and 4 min for lactose, respectively. Overall analysis time for three analytes with one sampling was less than 8 min without pretreatment and interference of electroactive compounds and substrates. Glucose, sucrose and lactose content of the model and food samples were measured with both the improved system and commercial enzyme kits. There was high correlation between the results. This gives us the opportunity to use the improved electrode system for determination of glucose, sucrose and lactose in food samples. Also this result was found to be very promising in extending the spectrum of detectable analytes simply by addition of new columns containing immobilised enzymes that are specific to target analytes.

Biotechnology↗

PubMed2002

A recombinant Saccharomyces cerevisiae strain for efficient conversion of lactose in salted and unsalted cheese whey into ethanol.

For utilization of lactose in salted and unsalted cheese whey, intergeneric protoplast fusion between lactose nonfermenting, salt-tolerant Saccharomyces cerevisiae ATCC4126 and lactose fermenting Kluyveromyces lactis CBS683 was carried out. The fusion process gave rise to new hybrid yeast strains that revealed higher significant DNA contents than parental strains. The recombinants showed growth on either lactose or sucrose. The ethanol yields by some recombinants were 5.55% from sweet whey and 4.66% from salted whey containing up to 6% sodium chloride compared to 4.15 and 2.86% for parental K. lactis CBS683, respectively.

Artificial Gene Fusion↗

PubMed2003

Hydrolysis of lactose by free and immobilized beta-galactosidase from Thermus sp. strain T2.

The hydrolysis of lactose by a beta-galactosidase from the thermophilic microorganism Thermus sp. strain T2, both in solution and immobilized on a commercial silica-alumina, has been studied. The enzyme has been previously produced by Escherichia coli JM101 harboring the plasmid pBGT1, which contains the codifying gene under the promoters lpp(P) and lac(PQ). The enzyme was immobilized on the support activated with tris-hydroxymethylphosphine (THP). Activity and stability of the free and the immobilized enzyme towards pH and temperature were tested. To study the activity at different pH and temperature values, lactose was used as substrate. To check the stability, the enzyme was incubated either in buffer BP or in a solution of lactose in buffer BM at different pH and temperatures, being the remaining activity tested by withdrawing samples and determining their activity toward ONPG at 70 degrees C in buffer BP. Afterward, runs were performed to obtain kinetic models adequate for the description of the hydrolysis of lactose by the free and the immobilized enzyme. These data were fitted to the kinetic models proposed (all based on the Michaelis-Menten mechanism) by non-linear regression, being the models and their parameters compared to determine the effect of the immobilization on the kinetic behavior of the enzyme. Both the free and the immobilized enzyme are competitively inhibited by galactose, while glucose inhibited only the action of the free enzyme, in an uncompetitive way. The immobilization step seems to eliminate the inhibition by glucose. Moreover, the immobilization reduced to a half the inhibitory action of galactose. In general, the immobilization reduced the activity of the enzyme, but increased its thermal stability. Finally, a comparison between the kinetic behavior of this thermophilic enzyme and enzymes of mesophile microorganisms previously studied by us (E. coli and K. fragilis) and by other authors (Aspergillus niger) is performed.

Enzyme Stability↗

PubMed2005

Synthesis of galacto-oligosaccharide from lactose using beta-galactosidase from Kluyveromyces lactis: Studies on batch and continuous UF membrane-fitted bioreactors.

A study of galacto-oligosaccharides (GOS) synthesis from lactose with beta-galactosidase from Kluyveromyces lactis (Maxilact L2000) was carried out. The synthesis was performed using various initial lactose concentrations ranging from 220 to 400 mg/mL and enzyme concentrations ranging from 3 to 9 U/mL, and was investigated at 40 degrees C and pH 7, in a stirred-tank reactor. In the experimental range examined, the results showed the amount of GOS formed depended on lactose concentration but not on enzyme concentration. Galactose was a competitive inhibitor, while glucose was a non-competitive inhibitor. In a further study, a laboratory-scale reactor system, fitted with a 10-kDa NMWCO composite regenerated cellulose membrane, was used in a continuous process. The reactor was operated in cross-flow mode. The effect of operating pressures on flux and productivity was investigated by applying different transmembrane pressures to the system. The continuous process showed better production performance compared to the batch synthesis with the same lactose and enzyme concentrations at 40 degrees C, pH 7. Comparison of product structures from batch and continuous processes, analyzed by HPAE-PAD and methylation analysis, showed similarities but differed from the structures found in a commercial GOS product (Vivinal GOS).

Bioreactors↗

PubMedDate not supplied

Acidifying enemas (lactitol and lactose) vs. nonacidifying enemas (tap water) to treat acute portal-systemic encephalopathy: a double-blind, randomized clinical trial.

A double-blind, controlled trial to study the efficacy of acidifying enemas of lactitol, a new galactoside-sorbitol disaccharide, and lactose vs. nonacidifying tap-water enemas was performed in 45 episodes of acute portal-systemic encephalopathy. At the time of randomization, all patients had encephalopathy of at least Grade 2+ severity, delay in the performance of number connection tests and hyperammonemia. A sequential analysis was performed which revealed after the inclusion of the first 20 patients, a significant failure of the nonacidifying enemas as compared to the lactitol enemas (p less than 0.004). The tap-water enema group was, therefore, suspended but the rest of the study continued after rerandomization for lactose and lactitol groups. A favorable response to treatment was obtained in 19 (86%) of the patients receiving lactitol enemas and in 14 (78%) of those receiving lactose enemas. A similar significant improvement in portal-systemic encephalopathy parameters and index was observed after both treatments. Both types of acidifying enemas induced a significant pH decrease in stool (p less than 0.05). These data suggest that acidifying agents like lactose and lactitol are effective and superior to tap-water enemas for the treatment of acute nitrogenous portal-systemic encephalopathy.

Ammonia↗

PubMed2002

Manipulating conformational equilibria in the lactose permease of Escherichia coli.

A mechanism proposed for lactose/H(+) symport by the lactose permease of Escherichia coli indicates that lactose permease is protonated prior to ligand binding. Moreover, in the ground state, the symported H(+) is shared between His322 (helix X) and Glu269 (helix VIII), while Glu325 (helix X) is charge-paired with Arg302 (helix IX). Substrate binding at the outer surface between helices IV (Glu126) and V (Arg144, Cys148) induces a conformational change that leads to transfer of the H(+) to Glu325 and reorientation of the binding site to the inner surface. After release of substrate, Glu325 is deprotonated on the inside due to re-juxtapositioning with Arg302. The conservative mutation Glu269-->Asp causes a 50-100-fold decrease in substrate binding affinity and markedly reduced active lactose transport, as well as decreased rates of equilibrium exchange and efflux. Gly-scanning mutagenesis of helix VIII was employed systematically with mutant Glu269-->Asp in an attempt to rescue function, and two mutants with increased activity are identified and characterized. Mutant Thr266-->Gly/Met267-->Gly/Glu269-->Asp binds ligand with increased affinity and catalyzes active lactose transport with a marked increase in rate; however, little improvement in efflux or equilibrium exchange is observed. In contrast, mutant Gly262-->Ala/Glu269-->Asp exhibits no improvement in ligand binding but a small increase in the rate of active transport; however, an increase in the steady-state level of accumulation, as well as efflux and equilibrium exchange is observed. Remarkably, when the two sets of mutations are combined, all translocation reactions are rescued to levels approximating those of wild-type permease. The findings support the contention that Glu269 plays a pivotal role in the mechanism of lactose/H(+) symport. Moreover, the results suggest that the two classes of mutants rescue activity by altering the equilibrium between outwardly and inwardly facing conformations of the permease such that impaired protonation and/or H(+) transfer is enhanced from one side of the membrane or the other. When the two sets of mutants are combined, the equilibrium between outwardly and inwardly facing conformations and thus protonation and H(+) transfer are restored.

Amino Acid Sequence↗

PubMed2001

One-step separation from lactose: recovery and purification of major cheese-whey proteins by hydroxyapatite--a flexible procedure suitable for small- and medium-scale preparations.

The recovery of cheese-whey proteins and lactose represents an important task both in environmental and in food sciences. Optimization of whey processing requires the quantitative separation of whey proteins from lactose, lower costs, harmless environmental impact, flexibility in protein recovery, and adaptability of the process to type and amount of available whey. Here we present a method based on the use of self-made, low-price, and nontoxic hydroxyapatite for one-step separation of lactose (non adsorbed) from bovine whey proteins (adsorbed). Recovery of proteins can be performed with high flexibility. Total protein fraction can be eluted with 0.4 M phosphate at pH 7.0. In alternative, proteins can be recovered in pairs with 0.4 M phosphate but at different pH's. About 56% of the proteins, primarily alpha-lactalbulmin and IgG, were eluted at pH 5.0. The other major proteins, beta-lactoglobulin and BSA, were eluted at pH 6.0. Fractions eluted with the two first eluants at pH 5.0 and pH 6.0 were applied to a Superdex 75 column for final purification by gel filtration. This method provides flexibility in whey protein recovery and quantitative separation of proteins from lactose before ultrafiltration and nanofiltration.

Animals↗

PubMed1982

Lactose absorption and malabsorption in healthy German children: improved phenotypic resolution by simultaneous determination of breath hydrogen and carbon dioxide.

A total of 124 apparently healthy German children aged 8 to 10 years were examined for lactose absorption employing the breath hydrogen test with multiple breath collection. Analysis of the maximal change of breath hydrogen concentration (delta maxH2) 110 and 150 min after a lactose load of 30 g failed to yield a bimodal distribution separating lactose absorbers and malabsorbers as observed in adults. Comparison with an adult control group of 120 subjects showed that the mean CO2 concentration was significantly lower and the coefficient of variation was considerably higher in the breath samples of the children. The difference between the highest and the lowest CO2 concentration in the three samples obtained from each individual was also significantly higher in the group of children. Normalizing the children's H2 concentration values to the mean CO2 concentration in the total group (3.04%) yielded a bimodal distribution of the delta maxH2 values. Of 124 children, 18 were identified as lactose malabsorbers. The 14.5% frequency is similar to that observed in German adults.

Air↗

PubMed1989

Influence of sugar source (lactose, glucose, galactose) on 2,3-butanediol production by Klebsiella oxytoca NRRL-B199.

The ability of Klebsiella oxytoca NRRL-B199 to use either lactose or the mixture of glucose and galactose as substrate for the production of 2,3-butanediol was studied in batch fermentations with different conditions of aeration and pH. 2,3-butanediol was undetected, or present in minute concentration in the fermentation broths with lactose, while it was the main product from glucose + galactose with final concentrations of up to 18.8g/l in media at pH 6.0. Under conditions optimal for 2,3-butanediol synthesis, when aeration limited growth, the rate of biomass growth was more tightly related to the aeration rate in lactose medium than in glucose + galactose medium. These relations suggest that the growth rate is very low on lactose but still considerable on glucose + galactose when aeration rate tends toward zero. Corresponding, the metabolism is more oxidative in the former medium, yielding mainly acetate as product.

Butylene Glycols↗

PubMed1993

Relationship between methane production and breath hydrogen excretion in lactose-malabsorbing individuals.

Recent studies have shown reduced breath hydrogen (H2) excretion in methane (CH4)-producing healthy individuals following ingestion of lactulose. This questions the reliability of the breath hydrogen test (BHT) in CH4 excretors, but the relationship between CH4 and H2 excretion in other clinical applications of the BHT is not known. We reviewed BHT results in two groups of subjects: (1) 385 children tested for lactose malabsorption in a hospital setting, and (2) 109 lactose-malabsorbing patients tested with a home kit. The percentage of lactose malabsorbers in group 1 (51%) was the same regardless of CH4-producing status (P = 0.97). The BHT data from group 2 showed a positive correlation (r = 0.6, P < 0.000001) between the magnitude of the rise in CH4 and H2 concentrations, and the H2 excretion curves were significantly higher in the CH4-producing individuals. We conclude that attention to CH4-producing status is not necessary in the interpretation of the lactose BHT.

Adolescent↗

PubMed1994

Prevalence of lactose maldigestion. Influence and interaction of age, race, and sex.

Ninety-eight adults ranging from 20 to 89 years in age (52 blacks, 46 whites, 48 males, 50 females) were tested for lactose maldigestion by breath hydrogen analysis after consuming milk containing 16.5 g lactose (360 ml milk). Older adults (> or = 50 years) displayed a significantly higher incidence (46%) of lactose maldigestion than younger adults (< 50 years, 26%). In younger adults there were 2.4 times more maldigesters in blacks than in whites, while in older groups this ratio was 3.6. Level of breath hydrogen significantly increased with age up to the age group of 60-69 years. The interaction between age groups and race was highly significant. Of the maldigesters, 63% reported symptoms and 3% of the total sample reported severe symptoms. Results of this study indicate that the prevalance of lactose maldigestion significantly increases with age in blacks compared to whites and that the magnitude of the problem may be greater in black maldigesters than in white maldigesters.

Adult↗

PubMed2006

A suppressor analysis of residues involved in cation transport in the lactose permease: identification of a coupling sensor.

Four amino acids critical for lactose permease function were altered using site-directed mutagenesis. The resulting Quad mutant (E269Q/R302L/H322Q/E325Q) was expressed at 60% of wild-type levels but found to have negligible transport activity. The Quad mutant was used as a parental strain to isolate suppressors that regained the ability to ferment the alpha-galactoside melibiose. Six different suppressors were identified involving five discrete amino acid changes and one amino acid deletion (Q60L, V229G, Y236D, S306L, K319N and DeltaI298). All of the suppressors transported alpha-galactosides at substantial rates. In addition, the Q60L, DeltaI298 and K319N suppressors regained a small but detectable amount of lactose transport. Assays of sugar-driven cation transport showed that both the Q60L and K319N suppressors couple the influx of melibiose with cations (H(+) or H(3)O(+)). Taken together, the data show that the cation-binding domain in the lactose permease is not a fixed structure as proposed in previous models. Rather, the data are consistent with a model in which several ionizable residues form a dynamic coupling sensor that also may interact directly with the cation and lactose.

Amino Acid Substitution↗

PubMed2002

Beta-galactosidase from a cold-adapted bacterium: purification, characterization and application for lactose hydrolysis.

The enzyme beta-galactosidase was purified from a cold-adapted organism isolated from Antarctica. The organism was identified as a psychotrophic Pseudoalteromonas sp. The enzyme was purified with high yields by a rapid purification scheme involving extraction in an aqueous two-phase system followed by hydrophobic interaction chromatography and ultrafiltration. The beta-galactosidase was optimally active at pH 9 and at 26 degrees C when assayed with o-nitrophenyl-beta-D-galactopyranoside as substrate for 2 min. The enzyme activity was highly sensitive to temperature above 30 degrees C and was undetectable at 40 degrees C. The cations Na+, K+, Mg2+ and Mn2+ activated the enzyme while Ca2+, Hg2+, Cu2+ and Zn2+ inhibited activity. The shelf life of the pure enzyme at 4 degrees C was significantly enhanced in the presence of 0.1% (w/v) polyethyleneimine. The pure beta-galactosidase was also evaluated for lactose hydrolysis. More than 50% lactose hydrolysis was achieved in 8 h in buffer at an enzyme concentration of 1 U/ml, and was increased to 70% in the presence of 0.1% (w/v) polyethyleneimine. The extent of lactose hydrolysis was 40-50% in milk. The enzyme could be immobilized to Sepharose via different chemistries with 60-70% retention of activity. The immobilized enzyme was more stable and its ability to hydrolyze lactose was similar to that of the soluble enzyme.

Acclimatization↗

PubMed1999

Construction of a flocculent Saccharomyces cerevisiae fermenting lactose.

A flocculent Saccharomyces cerevisiae strain with the ability to express both the LAC4 (coding for beta-galactosidase) and LAC12 (coding for lactose permease) genes of Kluyveromyces marxianus was constructed. This recombinant strain is not only able to grow on lactose, but it can also ferment this substrate. To our knowledge this is the first time that a recombinant S. cervisiae has been found to ferment lactose in a way comparable to that of the existing lactose-fermenting yeast strains. Moreover, the flocculating capacity of the strain used in this work gives the process several advantages. On the one hand, it allows for operation in a continuous mode at high cell concentration, thus increasing the system's overall productivity; on the other hand, the biomass concentration in the effluent is reduced, thus decreasing product separation/purification costs.

Kluyveromyces↗