Low Lactose Content Research Articles

The effect of lactose and inulin on intestinal morphology, selected microbial populations and volatile fatty acid concentrations in the gastro-intestinal tract of the weanling pig

AbstractTwenty piglets (21 days, 7·8 kg live weight (LW)) were used in a 2×2 factorial to investigate interactions between lactose and inulin on intestinal morphology, microbiology and volatile fatty acid (VFA) production of the weanling pig. The piglets were offered the following diets for 6 days and then sacrificed: (T1) 150 g/kg lactose, (T2) 150 g/kg lactose +15 g/kg inulin, ( T3) 330 g/kg lactose, and ( T4) 330 g/kg lactose +15 g/kg inulin. Tissue samples were taken from the duodenum, jejunum and ileum for morphological measurements. Digesta samples were taken from the ileum, caecum and colon. There was an interaction ( P<0·05) between lactose and inulin in villous height in the jejunum. The inclusion of inulin at 150 g/kg lactose increased villous height compared with 150 g/kg lactose without inulin. However, inulin had no effect on villous height at 330 g/kg lactose inclusion. There was a linear relationship between food intake and villous height in the duodenum (P<0·001, R2=0·45) and the jejunum (P< 0·01, R2=0·25). The inclusion of 330 g/kg lactose increased ( P<0·05) total VFA compared with 150 g/kg lactose in the caecum and the population of lactobacilli in the caecum and colon (P<0·1). There was an interaction (P<0·05) between lactose and inulin for total VFA concentration in the colon. The pigs receiving 330 g/kg lactose had a higher total VFA concentration compared with pigs on 150 g/kg lactose. However, there was no difference between 150 g/kg and 330 g/kg lactose when the diets were supplemented with inulin. In conclusion, the inclusion of high dietary concentrations of lactose resulted in increased lactobacilli and short-chain fatty acid concentrations. The inclusion of inulin with low dietary concentrations of lactose resulted in improved intestinal health through a reduction of intestinal pH and increases in villous height.

Statistical Modeling of β-galactosidase Inhibition During Lactose Hydrolysis

A statistical model approach called response surface methodology was used to describe the product and substrate inhibition effect on β-galactosidase enzyme during lactose hydrolysis. The effect of independent variables, namely the initial concentrations of lactose (73 – 146 mM), galactose (44 – 122 mM) and glucose (83 – 167 mM) on the reaction rate of β-galactosidase was evaluated. The enzymatic reaction rate was influenced by both combined and individual effects of all the substrate and products. Although, glucose acted as an activator at low lactose and low galactose concentrations, glucose caused the inhibition of β-galactosidase at higher concentrations of lactose and galactose. The effect of galactose concentration on β-galactosidase enzyme was in the direction of inhibition. At low lactose concentrations and high glucose concentrations, galactose concentration became more effective on the reaction rate.

Protein production by auto-induction in high-density shaking cultures

Inducible expression systems in which T7 RNA polymerase transcribes coding sequences cloned under control of a T7 lac promoter efficiently produce a wide variety of proteins in Escherichia coli. Investigation of factors that affect stability, growth, and induction of T7 expression strains in shaking vessels led to the recognition that sporadic, unintended induction of expression in complex media, previously reported by others, is almost certainly caused by small amounts of lactose. Glucose prevents induction by lactose by well-studied mechanisms. Amino acids also inhibit induction by lactose during log-phase growth, and high rates of aeration inhibit induction at low lactose concentrations. These observations, and metabolic balancing of pH, allowed development of reliable non-inducing and auto-inducing media in which batch cultures grow to high densities. Expression strains grown to saturation in non-inducing media retain plasmid and remain fully viable for weeks in the refrigerator, making it easy to prepare many freezer stocks in parallel and use working stocks for an extended period. Auto-induction allows efficient screening of many clones in parallel for expression and solubility, as cultures have only to be inoculated and grown to saturation, and yields of target protein are typically several-fold higher than obtained by conventional IPTG induction. Auto-inducing media have been developed for labeling proteins with selenomethionine, 15N or 13C, and for production of target proteins by arabinose induction of T7 RNA polymerase from the pBAD promoter in BL21-AI. Selenomethionine labeling was equally efficient in the commonly used methionine auxotroph B834(DE3) (found to be metE) or the prototroph BL21(DE3).

PC28 EFFECT OF A NEW INFANT FORMULAE ENRICHED PREBIOTICS, PROBIOTICS, NUCLEOTIDES AND LC-PUFA???S ON INFANTS RECOVERY AFTER AN INFECTION

Introduction: During first years of life, infections are one of the main causes of pathology. In this population, infections can produce lack of appetite, decrease in nutrients absorption and disturbances in fecal microflora. The aim of the study was to evaluate the effect of a new infant formulae enriched with prebiotics, probiotics, nucleotides and LC-PUFA’s with a low lactose content in infant recovery after different kind of infections (respiratory, digestive. . .). Methods: A multicentric, randomised, prospective outpatients clinical trial was conducted. 68 infants younger than 12 months with a non-severe infectious process were included in the study and distributed in 2 groups: control group and RE group. Infants younger than 4 months were fed with an infant formulae and infants from 5 to 12 months with a follow-on formulae. Control group infants were fed standard infant and follow-on formulae. RE group infants were fed with infant and follow-on formulae enriched with prebiotics (galactooligosaccharides, nucleotides and LC-PUFA’s and with a low level of lactose. Follow-on formula used in the feeding of infants of RE group contained also probiotics (Lactobacillus rhamnosus and Bifidobacterium infantis). Clinical symptoms and duration if the infection was recordered at days 0, 5, 10 and 15 to know the evolution of infants recovery. Results: The time of recovery of appetite was lower in RE group than in Control group (p<0,001) and also the weight recovery (p<0,0001). Appetite was recovered in day 6 in infants of RE group and in day 11 in Control group. Weight recovery took place in the 5th day in RE group and in day 12 in the Control group. Group RE showed a statistically significant reduction in the duration of digestive symptoms like vomiting and diarrhoeas (p=0,04) in comparison with Control group. The mean duration of diarrhoeas in Control group was of 9 days and 4,8 in RE group. Taken into account all the variables analysed, the global recovery of infants need a shorter period of time in group RE than in Control group (7,5 days for group RE and 11,7 days for Control group, p=0,0003). Conclusion: The new range of infant formulae enriched with prebiotics (galactooligosaccharides), probiotics (Lactobacillus rhamnosus and Bifidobacterium infantis), nucleotides and LC-PUFA’s with a low level of lactose has demonstrated to be useful in infant feeding for achieve a complete and fast recovery of infants suffering digestive or respiratory infections.

A new kinetic model of recombinant β-galactosidase from Kluyveromyces lactis for both hydrolysis and transgalactosylation reactions

Previous models based on the Michaelis–Menten kinetic equation, that glucose was not used as an acceptor, did not explain our experimental data for lactose conversion by a recombinant β-galactosidase from Kluyeromyces lactis. In order to create a new kinetic model based on the data, the effects of galactose and glucose on β-galactosidase activity were investigated. Galactose acted as an inhibitor at low concentrations of galactose and lactose, but did not inhibit the activity of β-galactosidase at high concentrations of galactose (above 50 mM) and lactose (above 100 mM). The addition of glucose at concentrations below 50 mM resulted in an increased reaction rate. A new model of K. lactis β-galactosidase for both hydrolysis and transgalactosylation reactions with glucose and lactose as acceptors was proposed. The proposed model was fitted well to the experimental data of the time-course reactions for lactose conversion by K. lactis β-galactosidase at various concentrations of substrate.

Use of Dry Milk Protein Concentrate in Pizza Cheese Manufactured by Culture or Direct Acidification

Milk protein concentrate (MPC) contains high concentrations of casein and calcium and low concentrations of lactose. Enrichment of cheese milk with MPC should, therefore, enhance yields and improve quality. The objectives of this study were: 1) to compare pizza cheese made by culture acidification using standardized whole milk (WM) plus skim milk (SM) versus WM plus MPC; and 2) compare cheese made using WM + MPC by culture acidification to that made by direct acidification. The experimental design is as follows: vat 1 = WM+ SM + culture (commercial thermophilic lactic acid bacteria), vat 2 = WM + MPC + culture, and vat 3 = WM + MPC + direct acid (2% citric acid). Each cheese milk was standardized to a protein-to-fat ratio of ∼1.4. The experiment was repeated three times. Yield and composition of cheeses were determined by standard methods, whereas the proteolysis was assessed by urea polyacrylamide gel electrophoresis (PAGE) and water-soluble N contents. Meltability of the cheeses was determined during 1 mo of storage, in addition to pizza making. The addition of MPC improved the yields from 10.34±0.57% in vat 1 cheese to 14.50±0.84% and 16.65±2.23%, respectively, in vats 2 and 3 and cheeses. The percentage of fat and protein recoveries showed insignificant differences between the treatments, but TS recoveries were in the order, vat 2>vat 3>vat 1. Most of the compositional parameters were significantly affected by the different treatments. Vat 2 cheese had the highest calcium and lowest lactose contencentrations. Vat 3 cheese had the best meltability. Vat 1 cheese initially had better meltability than vat 2 cheese; however, the difference became insignificant after 28 d of storage at 4°C. Vat 3 cheese had the softest texture and produced large-sized blisters when baked on pizza. The lowest and highest levels of proteolysis were found in vats 2 and 3 cheeses, respectively. The study demonstrates the use of MPC in pizza cheese manufacture with improved yield both by culture acidification as well as direct acidification.

Effects of Standardization of Whole Milk with Dry Milk Protein Concentrate on the Yield and Ripening of Reduced-Fat Cheddar Cheese

Commercial milk protein concentrate (MPC) was used to standardize whole milk for reduced-fat Cheddar cheesemaking. Four replicate cheesemaking trials of three treatments (control, MPC1, and MPC2) were conducted. The control cheese (CC) was made from standardized milk (casein-to-fat ratio, C/F ∼1.7) obtained by mixing skim milk and whole milk (WM); MPC1 and MPC2 cheeses were made from standardized milk (C/F ∼1.8) obtained from mixing WM and MPC, except that commercial mesophilic starter was added at the rate of 1% to the CC and MPC1 and 2% to MPC2 vats. The addition of MPC doubled cheese yields and had insignificant effects on fat recoveries (∼94% in MPC1 and MPC2 vs. ∼92% in CC) but increased significantly total solids recoveries (∼63% in CC vs. 63% in MPC1 and MPC2). Although minor differences were noted in the gross composition of the cheeses, both MPC1 and MPC2 cheeses had lower lactose contents (0.25 or 0.32%, respectively) than in CC (0.60%) 7 d post manufacture. Cheeses from all three treatments had ∼109 cfu/g initial starter bacteria count. The nonstarter lactic acid bacteria (NSLAB) grew slowly in MPC1 and MPC2 cheeses during ripening compared to CC, and at the end of 6 mo of ripening, numbers of NSLAB in the CC were 1 to 2 log cycles higher than in MPC1 and MPC2 cheeses. Primary proteolysis, as noted by water-soluble N contents, was markedly slower in MPC1 and MPC2 cheeses compared to CC. The concentrations of total free amino acids were in decreasing order CC>MPC2>MPC1 cheeses, suggesting slower secondary proteolysis in the MPC cheeses than in CC. Sensory analysis showed that MPC cheeses had lower brothy and bitter scores than CC. Increasing the amount of starter bacteria improved maturity in MPC cheese.

Effect of mastitis and related-germ on milk yield and composition during naturally-occurring udder infections in dairy cows

The effect of mastitis and related-germs on milk chemical composition (protein and lac- tose contents) and milk somatic cell count (SCC) was investigated in 501 milk quarter samples during two consecutive years in cows from three experimental herds. Each infected quarter was matched by a healthy one in the same udder, as a control. Milk protein and mineral assays were performed in a sub- sample of 128 milks. Staphylococci were the most frequently isolated germs (Staphylococcus aureus: 27%, coagulase-negative Staphylococci: 26%, Streptococci: 21%). Major milk pathogens (Staphylococcus aureus, Streptococcus uberis or Escherichia coli) associated with clinical signs of mastitis were accompanied by higher SCC (+1.6 log·mL -1 , P < 0.01), lower lactose concentration (-7.6 g·kg -1 , P < 0.01), higher protein concentration (+3.3 g·kg -1 , P < 0.01) and higher soluble protein concentrations (IgG and BSA), hence a sharp decrease in the casein/protein ratio (-10 percentage points, P < 0.01). Changes were more marked when Escherichia coli was present. Corynebacterium bovis did not alter milk chemical composition whereas coagulase-negative Staphylococci slightly re- duced lactose concentration (-1.8 g·kg -1 ) and increased SCC (+0.37 log·mL -1 ). Calcium and phos- phorus milk contents were hardly modified by the presence of microorganisms. The decrease in milk yield during clinical mastitis varied from 1.6 kg·d -1 in the presence of Staphylococcus aureus to 15 kg·d -1 in the presence of Escherichia coli.

Production of Oligosaccharides in Yogurt Containing Bifidobacteria and Yogurt Cultures

Yogurts were prepared by using yogurt cultures combined to mixed cultures of bifidobacteria (Bifidobacterium animalis, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium infantis, and Bifidobacterium longum) and by adding a preincubation step (1.5h at 50°C) with bifidobacteria to the conventional method of manufacture in order to produce oligosaccharides. The survival of bifidobacteria was drastically affected during storage of yogurts, except for products containing B. animalis, in which viable counts remained at >106 cfu/g after 28 d of storage at 4°C. Oligosaccharides with a degree of polymerization of 3 were produced during the preincubation step (0.31 to 0.68%), and the amount in the final products varied according to the species of bifidobacteria inoculated during the preincubation step or the concentration of bifidobacteria used as second inoculum during the fermentation process. In fact, the higher concentration of oligosaccharides measured at the end of the fermentation process (0.72%) and the 28 d-storage period (0.67%) was obtained for yogurts containing B. infantis. However, yogurts containing B. breve showed higher β-galactosidase activities and had lower lactose concentrations after the fermentation process and the storage period than the other yogurts. The use of a mixed cultures of bifidobacteria (B. animalis, B. infantis, or B. breve) thus allows the production of yogurts in which bifidobacteria can survive in relatively high cell numbers and contain appreciable amount of oligosaccharides.

A novel approach to the pulmonary delivery of liposomes in dry powder form to eliminate the deleterious effects of milling

The effect of lyophilization and jet‐milling on liposome integrity was investigated as a function of their ability to retain the encapsulated model drug on reconstitution of the dry products. The encapsulation efficiencies of the lyophilized and jet‐milled formulations were determined at various concentrations of lactose. Lyophilization resulted in considerable leakage of the model drug at lower concentrations of lactose, and jet‐milling further augmented the leakage for all the lyophilized formulations, with optimum retention obtained for formulations containing at least 10:1 molar ratio of lactose/lipid. In an attempt to overcome the deleterious effects of lyophilization and jet‐milling, the feasibility of formulating phospholipid‐based powders that result in spontaneous formation of liposomes in an aqueous environment has been investigated. Partitioning of three model drugs (viz., ciprofloxacin, CM3 peptide, and salbutamol sulfate) between the aqueous phase and spontaneously formed liposomes was determined in terms of encapsulation efficiency. The effects of several parameters, including lactose concentration, lipid composition, and lipid concentration on the encapsulation efficiency of these model drugs were investigated. The spontaneous formation of liposomes on dispersion of phospholipid‐based powder formulations was further evidenced by freeze–fracture scanning electron microscopy. This novel approach for the delivery of liposomes in dry powder form appears promising because lyophilization is not involved and jet‐milling of these powder formulations did not impact encapsulation efficiency. Jet‐milled phospholipid‐based powder formulations showed high encapsulation efficiencies of 96.2 ± 1.4% for ciprofloxacin, 100% for CM3 peptide, and 45.3 ± 3.1% for salbutamol sulfate compared with a high amount of leakage (> 50%) observed due to jet‐milling of lyophilized liposome formulations encapsulating ciprofloxacin.

Once-a-day milking: possible and profitable?

Once-a-day (OAD) milking offers a major opportunity to improve labour output on New Zealand farms. However few full lactation studies have been undertaken to investigate the effect of this strategy on the productivity of the farm system. A trial was established in 2000 to measure the effect of milking frequency and breed in farm systems where stocking rate was adjusted to equalise per hectare feed demand in different herds. There were four treatments: two herds of 35 Friesian and 42 Jersey cows, at 3.5 and 4.2 cows/hectare respectively, were milked OAD for the entire season. Another two herds of 30 Friesian and 36 Jersey cows, at 3.0 and 3.6 cows/ hectare respectively, were milked twice a day. A higher stocking rate was used for the two OAD herds in an attempt to compensate for the effects of the expected decrease in feed eaten. In the Jersey herd, milking OAD resulted in decreased milksolids (MS) yield per cow and per hectare of 22% and 9% respectively. In the Friesians the corresponding decrease was 31% per cow and 19% per hectare. OAD milking resulted in significantly higher protein and milksolids concentrations, and lower lactose concentration. Mean individual somatic cell count was significantly increased by OAD milking, despite the absence of any differences in levels of bacterial infections between herds. The reduction in MS yield per cow and per hectare was smaller for the Jersey herd than the Friesian herd, indicating that the Jersey cow is perhaps better suited to OAD milking. Keywords: farm system, Friesians, Jerseys, milksolids, milk composition, once-a -day milking, somatic cell count

High-efficiency synthesis of oligosaccharides with a truncated beta-galactosidase from Bifidobacterium bifidum.

An exceptionally large beta-galactosidase, BIF3, with a subunit molecular mass of 188 kDa (1,752 amino acid residues) was recently isolated from Bifidobacterium bifidum DSM20215 [Møller et al. (2001) Appl Environ Microbiol 67:2276-2283]. The BIF3 polypeptide comprises a signal peptide followed by an N-terminal beta-galactosidase region and a C-terminal galactose-binding motif. We have investigated the functional importance of the C-terminal part of the BIF3 sequence by deletion mutagenesis and expression of truncated enzyme variants in Escherichia coli. Deletion of approximately 580 amino acid residues from the C-terminal end converted the enzyme from a normal, hydrolytic beta-galactosidase into a highly efficient, transgalactosylating enzyme. Quantitative analysis showed that the truncated beta-galactosidase utilised approximately 90% of the reacted lactose for the production of galacto-oligosaccharides, while hydrolysis constituted a 10% side reaction. This 9:1 ratio of transgalactosylation to hydrolysis was maintained at lactose concentrations ranging from 10% to 40%, implying that the truncated beta-galactosidase behaved as a "true" transgalactosylase even at low lactose concentrations.

Nutritional Supplements Used in Weight-reduction Programs Increase Intestinal Gas in Persons Who Malabsorb Lactose

Objective To determine if ingestion of 2 doses of milk-based dietary supplements produce gaseous symptoms in subjects who malabsorb lactose. Design Randomized, controlled, crossover trial. Subjects/setting Ten community-based subjects who malabsorb lactose. Intervention Ingestion of 2 standard servings of milk-based supplements (a powder reconstituted in fat-free milk or a ready-to-drink preparation) or low-lactose control preparations. Main outcome measures Frequency of flatus passage and subjective impression of bloating, flatulence, and abdominal discomfort. Statistical analysis Wilcoxon signed-rank test. Results The high lactose content (27 g) of 2 servings of the powder-based supplement ingested without other food resulted in a marked increase in daily flatus passages from the basal level of 9.7±8.2 to 30±14 (mean ±SD), and a significant increase in the subjects’ perception of gas. In contrast, the lower lactose content (18.4 g) of 2 servings of a ready-to-drink supplement resulted in a flatus frequency of 17±10 (P=.14 vs baseline) and no significant increase in the perception of increased gas. Neither supplement resulted in a significant increase in bloating, abdominal pain, or diarrhea. The lactose content of the liquid supplement was reduced by 80% following overnight incubation with an over-the-counter lactase preparation. Applications/conclusions Persons who malabsorb lactose should be aware that sizable increases in rectal gas commonly occur when milk-based powders reconstituted in milk are used as meal replacements. In contrast, gas problems probably will be minor following ingestion of 2 doses of a ready-to-drink, milk-based supplement. The lactose content of these supplements can be markedly reduced by overnight incubation with over-the-counter lactase preparations, and this manipulation should be beneficial for subjects troubled by the increased gas caused by the consumption of lactose-containing supplements. J Am Diet Assoc. 2001;101:1447–1452.

Improved oligosaccharide synthesis by protein engineering of beta-glucosidase CelB from hyperthermophilic Pyrococcus furiosus.

Enzymatic transglycosylation of lactose into oligosaccharides was studied using wild-type beta-glucosidase (CelB) and active site mutants thereof (M424K, F426Y, M424K/F426Y) and wild-type beta-mannosidase (BmnA) of the hyperthermophilic Pyrococcus furiosus. The effects of the mutations on kinetics, enzyme activity, and substrate specificity were determined. The oligosaccharide synthesis was carried out in aqueous solution at 95 degrees C at different lactose concentrations and pH values. The results showed enhanced synthetic properties of the CelB mutant enzymes. An exchange of one phenylalanine to tyrosine (F426Y) increased the oligosaccharide yield (45%) compared with the wild-type CelB (40%). Incorporation of a positively charged group in the active site (M424K) increased the pH optimum of transglycosylation reaction of CelB. The double mutant, M424K/F426Y, showed much better transglycosylation properties at low (10-20%) lactose concentrations compared to the wild-type. At a lactose concentration of 10%, the oligosaccharide yield for the mutant was 40% compared to 18% for the wild-type. At optimal reaction conditions, a higher ratio of tetrasaccharides to trisaccharides was obtained with the double mutant (0.42, 10% lactose) compared to the wild-type (0.19, 70% lactose). At a lactose concentration as low as 10%, only trisaccharides were synthesized by CelB wild-type. The beta-mannosidase BmnA from P. furiosus showed both beta-glucosidase and beta-galactosidase activity and in the transglycosylation of lactose the maximal oligosaccharide yield of BmnA was 44%. The oligosaccharide yields obtained in this study are high compared to those reported with other transglycosylating beta-glycosidases in oligosaccharide synthesis from lactose.

Effect of feeding before, during and after milking on milk production and the hormones oxytocin, prolactin, gastrin and somatostatin.

Feeding during milking has been shown to influence milk production, milk flow and milking time as well as the secretion of the pituitary hormones oxytocin and prolactin, and the gastrointestinal hormone somatostatin. However, it is not known whether feeding before or after milking has any effect. The aim of the present study was to investigate how the timing of feeding relative to milking influences milk production and flow, milking time and hormone secretion. The trial was carried out over 9 weeks with 24 cows at varying stages of lactation. Each treatment period lasted for 3 weeks, including one registration week. The cows were fed ad lib. and were exposed to three treatments: feeding 1.5 h before milking (FBM), feeding at exactly the same time as milking (FDM) and feeding 1.5 h after milking (FAM). The most marked treatment effect was observed during morning milking. FDM resulted in higher milk production and higher yields of protein and lactose. FAM produced a lower fat yield and a lower fat content compared with FDM, and a lower lactose content than either FBM and FDM. Milking time was longer when cows were fed during milking, but no significant effects on milk flow were found. The amount of milk collected during the first 2 min of milking was lower when cows were fed after milking. Milking-related oxytocin and somatostatin secretion was lower in FAM than in FDM. The level of prolactin was lower when cows were fed before or after than during milking. More studies are needed to elucidate whether there is a long-term effect on milk production related to the discussed milking routines.

Non-equilibrium thermodynamics analysis of the transport properties of formed-in-place Zr(IV) hydrous oxide-polyacrylate membranes: III. Ternary lactose-NaCl-water solutions

A non-equilibrium thermodynamics approach using practical transport coefficients has been used to evaluate frictional coefficients for the dominant solute near infinite dilution of the minor solute in the high pressure nanofiltration of ternary lactose-NaCl-water solutions with Zr(IV) hydrous oxide-polyacrylate membranes at pH 8.0. In terms of the frictional coefficients, the observed increase in the passage of NaCl with increasing lactose concentration at low concentrations of lactose is attributed to larger decreases in the NaCl-membrane and NaCl-solvent couplings than the decrease in the solvent-membrane coupling. The observed small decrease in the passage of lactose with increasing NaCl concentration at low concentrations of NaCl is attributed to a larger increases in the lactose-membrane and lactose-solvent couplings than the increase in the solvent-membrane coupling. The use of practical transport coefficients to evaluate the frictional coefficients by this method is limited to solutions with large differences in the concentrations of the two solutes.

Oligosaccharide and alkyl β-galactopyranoside synthesis from lactose with Caldocellum saccharolyticum β-glycosidase

The synthetic utility of the thermostable β-glycosidase from Caldocellum saccharolyticum was investigated. The ability of the enzyme to catalyze oligosaccharide and β-galactopyranoside synthesis from lactose was compared with that of the readily commercially available, moderately thermostable β-galactosidase (β- d-galactoside galactohydrolase, EC 3.2.1.23) from Aspergillus oryzae. Generally, the C. saccharolyticum enzyme showed significantly greater resistance to inactivation by heat and organic solvent and better yields of product. Although the A. oryzae enzyme gave better oligosaccharide yields at lower lactose concentrations, at higher concentrations (above 50% w/w) the C. saccharolyticum enzyme was significantly better, yielding a sugar mixture containing 42% by weight of tri- plus tetra-saccharides, from a 70% w/w lactose solution, compared with 31% by weight of oligosaccharides with the A. oryzae enzyme. In ethyl galactoside synthesis from ethanol and lactose, neither enzyme appeared to hydrolyze the product to any great extent. Under all conditions tested, the product yield did not peak, even at long reaction times, when most of the lactose had been consumed. The C. saccharolyticum enzyme, however, gave slightly higher product yields and could be used at higher ethanol concentrations without serious loss of activity.

Evaluation of bulk milk analyses of acetone, urea, and the fat-lactose-quotient as diagnostic aids in preventive veterinary medicine.

The purpose of this study was to evaluate the use of additional acetone and urea analyses to the established milk quality system (protein, fat, lactose, and somatic cell count) in bulk milk samples twice a month. Samples were obtained from 44/93 herds in a lowland/highland area. When ranging herds with most acetone values over 0.24mmol/1 (90th percentile), only two out of 10 herds would be on a corresponding list when ranged for highest ketosis treatment incidence. Most high acetone values occur after periods with concentrated calvings, but also in periods without calvings, presumably because of feeding with inferior silage high in butyric acid. Milk fat concentration, milk lactose concentration and the interaction term between these, the fat-lactose-quotient, show the largest absolute values in all three models with ketosis treatment incidence, milk protein concentration, and milk yield as dependent variables in general linear analyses on standardized variables. Acetone and urea concentrations in bulk milk show only small absolute values or are omitted from the models. The practical conclusion from these analyses on bulk milk samples to be used by advisory personnel is small, but it seems that high bulk milk fat concentrations and low lactose concentrations are unfavourable when it comes to ketosis treatment incidence, but favourable when it comes to milk protein concentration. Bulk milk acetone concentrations as a measure of the energy supply in herds must only be interpreted after calving intensity and silage quality are assessed.

Physical and storage properties of high milk protein powder

Abstract High milk protein powder (HMPP) was prepared by ultrafiltration and diafiltration of skim milk to 21% protein and spray drying. The HMPP had lower loose and packed densities than non-fat dry milk (NDM) but the true densities of both powders were similar. The solubility index (SI) rose in HMPP when stored above 10 °C but remained unchanged in NDM, regardless of storage temperatures. No hydroxymethylfurfural (HMF) was detected in HMPP stored at −20 to 45 °C for up to 3 1 2 months, however, HMF increased in NDM. The absence of HMF in HMPP may be in part attributed to its low lactose content.

Changes in bovine mammary-secretion composition during early involution following intramammary infusion of recombinant bovine cytokines.

This study was designed to determine whether intramammary infusion of recombinant bovine interleukin-1 beta or interleukin-2 had any adverse influence on bovine mammary function during the early non-lactating period. Mammary glands of eight Jersey cows were infused with either 10 micrograms of interleukin-1 beta or 1.0 mg of interleukin-2 following abrupt cessation of milking. Mammary secretions from each gland were collected from cows frequently during early involution and evaluated for changes in secretion composition. Percentage of milk fat and solids-not-fat during the experimental period was variable for all treatments. Percentage of protein increased throughout the study for all treatments, but mammary glands treated with interleukin-1 beta had higher protein percentages. All interleukin-treated mammary glands had lower concentrations of lactose than controls. Mammary secretions from interleukin-1 beta treated glands had higher concentrations of lactoferrin at 7 and 14 days of involution. Similarly, mammary secretions from interleukin-2 treated glands had higher concentrations of serum albumin on day 3 of involution and throughout the remainder of the study. Concentration of citrate and the citrate: lactoferrin molar ratio generally decreased throughout the study for all treatment groups. Concentration of alpha-lactalbumin in mammary secretions decreased throughout the study and was not different between treatment groups. Though significant changes in mammary secretion composition due to the presence of cytokines were observed in this study, resulting in an apparent acceleration of involution, there was no indication that these changes adversely affected normal bovine mammary function during the early non-lactating period.