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PubMed2001

The effect of co-spray drying with polyethylene glycol 4000 on the crystallinity and physical form of lactose.

The effect of spray drying lactose alone and in the presence of polyethylene glycol 4000 was investigated. Lactose was added to distilled water to give concentrations of 10, 20, 30 and 40g/100ml at room temperature and each spray dried in turn. Identical samples were prepared to which polyethylene glycol (PEG) 4000 was added (12% by weight of lactose) prior to spray drying. Microcalorimetric and X-ray diffraction studies showed that spray drying lactose solutions produced completely amorphous material due to rapid solidification during the spray drying process, whereas lactose suspensions yielded partially crystalline products due to crystalline material that remained in suspension. However, all the PEG/lactose (12%w/w) co-spray dried products were found to be crystalline. It can be inferred that the solidification rates of the lactose in the presence of PEG must have been slower than that of lactose alone which allowed PEG and lactose to crystallize. The PEG/lactose products that were spray dried from solution consisted of alpha-anhydrous, alpha-monohydrate, beta-lactose and PEG extended chain polymorph, whereas those formed from suspension PEG/lactose samples consisted of only alpha-anhydrous, alpha-monohydrate and extended chain PEG crystals. PEG probably caused the more concentrated lactose suspensions to crystallize slowly due to the strong hydrogen bonding between PEG and water, which allowed growth on the alpha-lactose seed crystals.

Calorimetry, Differential Scanning↗
PubMed2006

Third-generation biosensor for lactose based on newly discovered cellobiose dehydrogenase.

The present paper describes the principle and characteristics of a biosensor for lactose based on a third-generation design involving cellobiose dehydrogenase. As resulted from a previous comparative study (submitted manuscript), the novelty of this lactose biosensor is based on highly efficient direct electron transfer between two newly discovered cellobiose dehydrogenases (CDH), from the white rot fungi Trametes villosa and Phanerochaete sordida, and a solid spectrographic graphite electrode. CDH was immobilized on the electrode surface (0.073 cm2) by simple physical adsorption, and the CDH-modified electrode was next inserted into a wall-jet amperometric cell connected on-line to a flow injection setup (0.5 mL x min(-1)). The P. sordida CDH-based lactose biosensor, proved to be the better one, has a detection limit for lactose of 1 microM, a sensitivity of 1100 microA x mM(-1) x cm(-2), a response time of 4 s (the time required to obtain the maximum peak current), and a linear range from 1 to 100 microM lactose (correlation coefficient 0.998). The simplicity of construction and analytical characteristics make this CDH-based lactose biosensor an excellent alternative to previous lactose biosensors reported in the literature or commercially available. The CDH-lactose sensor was used to quantify the content of lactose in pasteurized milk, buttermilk, and low-lactose milk, using the standard addition method. No effects of the samples matrixes were observed. The operational stability of the sensor was tested for 11 h by continuous injection of 100 microM lactose (290 injections). The final signal of the sensor was maintained at 98% of its initial signal, with a low standard deviation of 1.72 (RSD 2.41%).

Animals↗
PubMed2003

Applicability of short hydrogen breath test for screening of lactose malabsorption.

The gold standard for diagnosing lactose malabsorption is the H2 hydrogen breath test (HBT). Different methods of HBT have been proposed. However, in clinical practice the HBT is often shortened to 1-2 hr without proper validation. Our objective was to establish whether the usefulness of the HBT is influenced by shortening of the test and/or by substrate variations. In 62 patients with clinically suspected lactose intolerance and a positive lactose HBT we calculated the sensitivity of the HBT depending on the duration of the HBT. To determine whether substrate variations influence the sensitivity of the HBT, in another group of 32 patients with clinically suspected lactose intolerance and a positive milk HBT, the sensitivity of the HBT was also calculated depending on the duration of the test after milk ingestion. In other unselected 97 individuals, the result of the HBT with 360 ml of whole milk supplemented with lactose was compared with a symptomatic score for lactose intolerance to evaluate the specificity of the shortened milk HBT. Breath H2 excretion was significantly higher after lactose than after milk load (P < 0.01), and the increase in H2 appeared earlier with lactose than with milk (60 vs 90, min respectively). HBT duration influenced the sensitivity of the test that decreased from 95% for the 3-hr HBT to 37% for the 1-hr HBT with lactose and from 80% for 3-hr HBT to 21% for 1-hr HBT with milk. The specificity was similar for the 3-hr milk HBT and the 5-hr test (67 vs 62%). In conclusion, for screening of lactose malabsorption, the HBT can be shortened to 3 hr without loss of sensitivity and specificity, when a high dose of lactose load is used.

Adult↗
PubMed1999

Autoregulation of lactose uptake through the LacY permease by enzyme IIAGlc of the PTS in Escherichia coli K-12.

Bacterial growth on one or more carbon sources requires careful control of the uptake and metabolism of these carbon sources. In Escherichia coli, the phosphorylation state of enzyme IIAGlc of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) is involved in this control in two ways. The unphosphorylated form of IIAGlc causes 'inducer exclusion', the inhibition of uptake of a number of non-PTS carbon sources, including lactose uptake by the lactose permease. The phosphorylated form of enzyme IIAGlc probably activates adenylate cyclase. In cells growing on lactose, enzyme IIAGlc was approximately 50% dephosphorylated, suggesting that lactose could inhibit its own uptake. This inhibition could be demonstrated by comparing lactose uptake rates in the wild-type strain and in a mutant in which the lactose carrier was insensitive to inducer exclusion. In this deregulated mutant strain, lactose was consumed much faster, and large amounts of glucose were excreted. It was shown that enzyme IIAGlc was dephosphorylated more strongly and that the cAMP level was lower in the mutant, most probably causing the observed decrease in lac expression level. When the lac expression level in the mutant strain was increased to that of the parent strain by adding exogenous cAMP, growth on lactose was slower, suggesting that enzyme IIAGlc-mediated inhibition of lactose uptake and downregulation of the lac expression level protected the cells against excessive lactose influx. An even stronger increase in the lac expression level in a mutant lacking enzyme IIAGlc caused complete growth arrest. We conclude that the autoregulatory mechanism that controls lactose uptake is an important mechanism for the cells in adjusting the uptake rate to their metabolic capacity.

Cyclic AMP↗
PubMed2000

Temperature- and moisture-induced crystallization of amorphous lactose in composite particles with sodium alginate prepared by spray-drying.

The purpose of this study was to investigate the temperature- and moisture-induced crystallization of amorphous lactose in the composite particles prepared by spray-drying an aqueous solution of crystalline lactose and sodium alginate. The temperature-induced crystallization of amorphous lactose in the composite particles was suppressed by increasing the amount of sodium alginate in the particles. The stabilizing effect of sodium alginate on amorphous lactose in the composite particles was greater than that in physical mixtures having the same formulating ratios. The improved stability of amorphous lactose in the composite particles was attributed to an increase in the glass transition temperature (Tg) of the mixture. Moisture-induced crystallization of amorphous lactose was also retarded by increasing the amount of sodium alginate in composite particles. Although the Tg of the mixture was reduced by increasing the water content of the particles, the values were higher than that of 100% amorphous lactose when particles of the same water content were compared. The change in the Tg of the composite particles with increasing water content was interpreted as involving three components of the Gordon-Taylor equation. In the amorphous lactose-sodium alginate systems, the Tg values of the composite particles containing sodium alginate were higher than the theoretical line predicted by two components of the Gordon-Taylor equation. These results suggested that there was a specific interaction between the sodium alginate and lactose molecules. This specific interaction was suggested by the fact that only very little amorphous lactose was measured in the spray-dried composite particles stored under humid conditions using differential scanning calorimetry. This molecular interaction may also be partly responsible for the suppression of both the temperature- and moisture-induced crystallization of amorphous lactose in the composite particles.

Alginates↗
PubMed1997

Urinary lactose: changes postpartum and relation with breast milk production.

Measurement of milk intake by breast-fed infants is difficult and a simple measure would be helpful for research and clinical practice. Maternal urinary lactose excretion has been proposed as a simple measure of lactation performance. The objectives of this study were to describe the pattern of urinary lactose excretion postpartum, and to determine whether lactose excretion could predict breast milk output. Lactose excretion was determined in 50 lactating and 49 nonlactating women at 0.5, 3, and 6 mo postpartum, and in 29 weaning women and 30 nonlactating women at 5, 8, and 11 mo postpartum. Lactose excretion was 4- to 17-fold higher in lactating than in nonlactating women, depending on the time point studied, and was highest in both groups 0.5 mo postpartum. Lactose excretion decreased after weaning but remained higher than in nonlactating women 1.3 mo after weaning was completed. Sixty-two additional women between 1.5 and 12 mo postpartum were studied to determine the ability of urinary lactose to predict milk output. There was a positive association between milk output and urinary lactose excretion, with correlation coefficients ranging from 0.17 to 0.30 depending on the measurement interval for lactose excretion. Lactose excretion could explain 2-9% of the variance in milk output, and could correctly classify 29-40% of individuals into tertiles of milk output. Although urinary lactose excretion reflects changes in biological activity of the mammary gland and gross changes in milk production, it is not a precise predictor of milk output.

Adult↗
PubMedDate not supplied

Lactose malabsorption and intolerance in Uruguayan population by breath hydrogen test (H2).

This study of 200 Uruguayans between 0 and 86 years old was designed to determine the prevalence of lactose malabsorption. Lactose intolerance is defined as a clinical syndrome of abdominal pain, diarrhea, flatulence, and bloating after the ingestion of a standard lactose tolerance test dose (2 g of lactose per kilogram of body weight or 50 g/m2 of body surface area, maximum 50 g in a 20% water solution). Lactose malabsorption refers to the state in which dietary lactose remains unhydrolyzed and subsequently unabsorbed from the gastrointestinal tract; symptoms may or may not result from lactose malabsorption. The technique of breath hydrogen (H2) was used after ingestion of 2 g/kg body weight to a maximum of 50 g in a 20% solution. There was no lactose malabsorption in children younger than 5 years old. The prevalence increases progressively after the age of 5, and in adolescence the percentage of malabsorption is similar to that in adults, who show 65% lactose malabsorption, with 25% asymptomatic and 40% intolerant. In 109 white adults, the prevalence of lactose malabsorption is 63%, with 24% asymptomatic and 39% intolerant. In 11 black adults, lactose malabsorption is 82%, with 27% asymptomatic and 55% intolerant. The difference between white and black adults is statistically significant (p less than 0.05). The H2 test is simple, reliable, noninvasive, and appropriate to study large populations.

Adolescent↗
PubMed1995

Review article: the treatment of lactose intolerance.

While about 50 million Americans malabsorb lactose, the colonic metabolism of this disaccharide may prevent the symptomatic state known as lactose intolerance. Elucidation of the clinical importance of lactose malabsorption requires comparison of symptoms after ingestion of lactose with those following an identical appearing lactose-free control. This paper reviews the extensive literature concerning lactose-induced symptoms and the value of lactose digestive aids. Poorly controlled studies have suggested that a cup of milk results in appreciable symptoms in the majority of lactase-deficient subjects. In contrast, controlled trials in unselected lactose malabsorbers of subjects claiming severe lactose intolerance indicate that symptoms from a cup of milk are no greater than that with a lactose-hydrolyzed control. An increasing fraction of subjects experience symptoms as the lactose load is increased, with the majority having symptoms when the equivalent of 1 L of milk is ingested as a single dose. Further studies are required to determine the tolerance to several cups of milk taken throughout the day. Available digestive aids include pre-hydrolyzed milk and lactase preparations that can be added to milk (which is then incubated) or ingested with milk. While these products are effective in reducing symptoms, it should be emphasized that there appears to be no need for these preparations when the dosage of milk is limited to one cup per day.

Humans↗
PubMed1986

Incomplete lactose absorption from breast milk during acute gastroenteritis.

The incidence and degree of incomplete lactose absorption was investigated in breast fed infants and children up to two years of age during acute gastroenteritis (GE). Lactose absorption was assessed in 50 patients by means of the hydrogen breath test (HBT), approximately 5.5 days after the admission to hospital. HBT detected incomplete lactose absorption of marked (lactose malabsorption) and probably mild degree in 8 and 6 patients respectively. Incomplete lactose absorption appeared to be transient in all 5 patients retested after discharge. HBT failed to identify 8 cases of lactose intolerance which were detected by investigation of the stools. In 31 breast fed controls of a similar age range incomplete lactose absorption of only mild degree was probably present in 2 and lactose intolerance in 1, which too was only detected by investigation of stools. During acute GE the use of HBT is appropriate to detect milder forms of incomplete lactose absorption than lactose intolerance. For the detection of lactose intolerance the measurement of pH and reducing substances in the stools remains the method of choice. The findings are in favour of the continuation of breast feeding during acute GE.

Acute Disease↗
PubMed1984

Lactose in plasma during lactogenesis, established lactation and weaning in sows.

The concentration of lactose in plasma was determined in different sows at all phases of their reproductive cycle and related to the compositional changes in mammary secretion during lactogenesis, established lactation and weaning. Lactose was present in low concentrations (3-4 microM) in the blood of virgin sows and pregnant sows up to 107 days of gestation. From day 4 pre-partum to day 1 pre-partum circulating lactose rose gradually to 34.5 +/- 7.7 microM (mean +/- S.E. of mean). Maximal concentrations of 262 +/- 168.4 microM were reached 6 h after parturition. The concentration of lactose in plasma was correlated with the amount of lactose in mammary secretion (r = 0.88, P less than 0.01) at the beginning of farrowing. During established lactation the concentrations of lactose, Na and K in milk, and of lactose in plasma (72-86 microM), were constant. The concentration of lactose in plasma did not vary significantly during periods of suckling, or after stimulation of milk ejection by oxytocin. However, the amount of lactose in plasma rose significantly (P less than 0.02) after the administration of oxytocin if milk ejection was not accompanied by suckling. The mean plasma concentration of lactose began to rise 36 h after weaning to a peak value of 241.8 +/- 53.6 microM at 48 h; thereafter it declined to 10.2 +/- 2.0 microM by 6 days. This study has shown that lactose concentrations in the plasma vary according to the secretory activity of the mammary gland. Its plasma concentration provides an earlier temporal measure of lactogenesis in individual sows than is obtained either from observation or analysis of mammary secretion.

Animals↗
PubMed1981

Properties of the lactose transport system in Klebsiella sp. strain CT-1.

Highly purified [D-glucose-1-14C]lactose has been used to study the transport of lactose by Klebsiella sp. strain CT-1. Strain CT-1 transports lactose by a lactose-inducible system that exhibited an apparent Km of 6 mM lactose and an apparent Vmax of 140 nmol/min per mg of cell protein. Lactose uptake was inhibited competitively by o-nitrophenyl-beta-D-galactoside with a Ki value of 8 mM, but was not inhibited by thio-beta-methyl-galactoside. D-Glucose, D-mannose, 2-deoxyglucose, and alpha-methyl-D-glucoside also inhibited lactose uptake. Phosphoenolpyruvate-dependent hydrolysis of o-nitrophenyl-beta-D-galactoside and lactose-dependent release of pyruvate from phosphoenolpyruvate by benzene-treated CT-1 cells showed that CT-1 transports lactose by a phosphoenolpyruvate:sugar phosphotransferase system. Correlations between the growth rate of CT-1 on lactose and properties of the transport system indicated that transport is the rate limiting step in utilization of lactose.

Biological Transport↗
PubMed1995

Novel products and new technologies for use of a familiar carbohydrate, milk lactose.

The cheese industry produces large amounts of lactose in the form of cheese whey and whey permeate, generating approximately 27 million tonnes/yr in the US alone. Many uses have been found for whey and lactose, including uses in infant formula; bakery, dairy, and confectionery products; animal feed; and feedstocks for lactose derivatives and several industrial fermentations. Lactose use in food products, however, is somewhat limited because of its low solubility and indigestibility in many individuals. For this reason, lactose is often hydrolyzed before use. Still, demand is insufficient to use all available whey lactose. The result is a low market value for lactose; almost half of the whey produced each year remains unused and is a significant waste disposal problem. Several approaches are possible for transforming lactose into value-added products. For example, galactooligosaccharides can be produce through enzymatic treatments of lactose and may be used as a probiotic food ingredient. Organic acids or xanthan gum may be produced via whey fermentation, and the fermented whey product can be used as a food ingredient with special functionality. This paper reviews the physical characteristics, production techniques, and current uses of lactose, whey, and lactose derivatives. Also examined are novel fermentation and separation technologies developed in our laboratory for the production of lactate, propionate, acetate, and xanthan gum from whey.

Animal Feed↗
PubMed1982

The effect of lactose supplementation and source on feed intake and production characteristics of laying hens.

Three experiments involving a total of 550 laying hens were conducted to study the effects of low level lactose feeding on the egg production characteristics of laying hens. The specific purposes were to determine if lactose influenced calcium utilization and feed intake and if there were any important interactions between lactose and calcium. There was a consistent significant improvement in egg shell breaking strength as a result of lactose supplementation. One percent dietary lactose appeared to be adequate to achieve this improvement. The addition of 2 or 3% lactose did not result in any greater improvement than 1%. There were no consistent influences of lactose, lactose source, or calcium level on feed intake or any of the other variables examined in the three experiments. As was expected, 61-week-old hens laid significantly fewer and larger eggs with weaker shells than 47-week-old hens. There were four statistically significant interaction effects: lactose level X calcium level on egg production; lactose level X calcium level on egg shell strength; and age X lactose level on egg shell strength. Even though these effects were statistically significant, it is questionable whether or not they are of practical importance in feeding laying hens.

Animals↗
PubMed1992

Fermentation of [14C]lactose in broiler chicks by cecal anaerobes.

Volatile fatty acids and lactic acid were products of [14C]lactose metabolism in 10-day-old broiler chicks. The [14C]lactose and unlabeled lactose were given to chicks in combination with cultures of cecal anaerobes (direct fed microbials) from adult broiler chickens. Aliquots of these cecal anaerobes had been used previously to reduce Salmonella typhimurium colonization in broiler chicks. In the current study, chicks were treated with anaerobes and anaerobes plus lactose on the day of hatch. Chicks given lactose plus anaerobes also received unlabeled lactose in the drinking water. Chicks in all treatment groups received [14C]lactose on Day 10 posthatch. After 5 h, most of the radiolabel was detected in the foregut and intestine. Significantly lower concentrations of [14C]lactic acid were detected in the serum and foregut of chicks given anaerobes and anaerobes plus lactose than in the similar samples from control chicks. Additionally, significantly less [14C]lactic acid was detected in the feces of chicks treated with anaerobes plus lactose than in feces from control chicks and chicks receiving only anaerobes. Significant differences in the total content of volatile fatty acids and lactic acid were detected in the serum, liver, intestine, and ceca of chicks treated with anaerobes or anaerobes plus lactose. These data indicate that cecal flora utilize lactose to produce volatile fatty acids and lactic acid.

Animals↗
PubMed1989

[Selection of methods of detecting lactose-fermenting Salmonella strains and evaluating their usefulness for diagnostic studies].

Salmonella rods of subspecies I, lactose-fermenting were first isolated in Poland in 1980. They were isolated from a plus sample taken from a brain abscess of a child. Next strains were isolated from faeces of newborn and hospitalized children. Growth characteristic of colonies of lactose-fermenting Salmonella strains on selective-differentiating media (Mac Conkey's Levine, SS, Sołtys) recommended for inoculation of clinical material resembled Escherichia coli. So far these type of colonies were omitted in diagnostic examinations. Lactose-fermenting variants showed on Bismuth sulfate agar "Difco" (WB) typical for Salmonella growth pattern. They grew on this medium after 48 hr of incubation in a form of black, medium sized colonies, with some metallic brilliance and characteristic blackening of the medium undercolonies. Precise knowledge of biochemical properties of lactose-fermenting Salmonella allows to supplement so far used diagnostic scheme with additional tests permitting differentiation of lactose-fermenting variants of Salmonella from the other members of Enterobacteriaceae family. Taking into consideration biochemical variants in diagnostic procedure i.e. lactose-fermenting Salmonella, allowedns to isolate in the years 1983-1985 lactose-positive strains in 1305 out of 2773 (47%) individuals positive for S. agona. In 1987, 246 persons (28.3%) out of 869 with lactose-fermenting Salmonella of various serotypes were simultaneously infected with lactose-negative variant. Lactose-fermenting strains of Salmonella belonged most frequently to the following genera: S. agona, S. enteritidis, S. oranienburg, S. typhimurium, and S. goldcoast. It was found that the modified diagnostic procedure makes possible the isolation and the identification of lactose-positive varians of Salmonella.

Bacteriological Techniques↗
PubMed1985

Lactose malabsorption in Israeli children.

Lactose malabsorption during childhood was studied in 110 Jewish children in Israel, using the lactose hydrogen breath test. Sixty-eight subjects (61.8%) were lactose malabsorbers, 41 (60.3%) of whom were lactose-intolerant with symptoms evidenced during or following the tests, whereas 27 (39.7%) were symptom-free (tolerant malabsorbers). In the youngest age-group (4 months to 3 years), no lactose malabsorption was detected, whereas in the higher age-groups the prevalence of lactose malabsorption increased with age. The percentages of lactose malabsorption in the age-groups 3 to 6, 6 to 12 and 12 to 16 years were 56.5, 65.2 and 75.0%, respectively. The percentages of lactose-intolerant subjects also increased in the same age-group, to 26.5, 39.1 and 65.0%. There were no significant differences in lactose malabsorption and tolerance between the various ethnic groups tested. The peak values of breath hydrogen were higher in lactose-intolerant than in lactose-tolerant malabsorbers.

Adolescent↗
PubMed1997

Phylogenetic analysis of the evolution of lactose digestion in adults.

In most of the world's population the ability to digest lactose declines sharply after infancy. High lactose digestion capacity in adults is common only in populations of European and circum-Mediterranean origin and is thought to be an evolutionary adaptation to millennia of drinking milk from domestic livestock. Milk can also be consumed in a processed form, such as cheese or soured milk, which has a reduced lactose content. Two other selective pressures for drinking fresh milk with a high lactose content have been proposed: promotion of calcium uptake in high-latitude populations prone to vitamin-D deficiency and maintainance of water and electrolytes in the body in highly and environments. These three hypotheses are all supported by the geographic distribution of high lactose digestion capacity in adults. However, the relationships between environmental variables and adult lactose digestion capacity are highly confounded by the shared ancestry of many populations whose lactose digestion capacity has been tested. The three hypotheses for the evolution of high adult lactose digestion capacity are tested here using a comparative method of analysis that takes the problem of phylogenetic confounding into account. This analysis supports the hypothesis that high adult lactose digestion capacity is an adaptation to dairying but does not support the hypotheses that lactose digestion capacity is additionally selected for either at high latitudes or in highly arid environments. Furthermore, methods using maximum likelihood are used to show that the evolution of milking preceded the evolution of high lactose digestion.

Adult↗
PubMed1989

Breath hydrogen excretion after lactose and whole milk ingestion. A prospective comparison in lactase deficiency.

As the 50 g of lactose in the usual clinical test is unphysiologic both because it is equivalent to 1 L milk and because the usual dietary intake is not the purified sugar, but milk, we undertook a prospective comparison of the absorption of lactose after both lactose and milk ingestion with an equivalent lactose content. We studied 51 healthy volunteers, using the hydrogen breath test technique. All patients received 25 g lactose in aqueous solution. Subjects with an abnormal test had the test repeated with 500 ml whole cow's milk, whereas subjects with a normal test repeated the test after ingesting the unabsorbable sugar lactulose to detect the capacity of their colonic flora to produce the gas. Symptoms of gastrointestinal intolerance were also recorded. Compared to an equivalent lactose amount, milk lactose is better absorbed (8% of the entire population malabsorbed 500 ml whole milk, whereas 33.33% malabsorbed 25 g lactose) and induces intolerance in fewer subjects. We conclude that milk rather than pure lactose must be used in clinical evaluation of lactose malabsorption and intolerance.

Adult↗