Journal of Dairy Research

Published by Cambridge University Press

Online ISSN: 1469-7629


Print ISSN: 0022-0299


Fig. 1. Structure of the DNA regions containing the goat CSN1S1 (A and 01 alleles) and CSN2 genes and location of primers. 
Fig. 2. Partial sequence of the 12th exon and 12th intron of the CSN1S1 A (EMBL acc.n8 AJ252127) and CSN1S2 01 (EMBL acc.n8 AJ252126) alleles. AS-PCR primers are underlined. 
Fig. 3. DNA electrophoretic patterns of the amplified fragments characterizing the goat CSN1S1 A and CSN1S1 01 alleles. M = Marker 50 bp (Promega); lane 1: CSN1S1 A/A ; lane 2: CSN1S1 A/0 1 ; lane 3: CSN1S1 0 1 /0 1 . 
Molecular characterization of the goat CSN1S1(01) allele
  • Article
  • Full-text available

June 2003


831 Reads


Rosa Illario





Caseins (α s1 , β, α s2 , e κ) represent about 80% of the whole protein content of ruminant milk. Each of these proteins is encoded by single copy genes ( CSN1S1 , CSN2 , CSN1S2 and CSN3 , respectively) clustered on a ∼200-kb segment of chromosome 6 (Ferretti et al. 1990; Gallagher et al. 1994) in the order: CSN1S1 , CSN2 , CSN1S2 and CSN3 (Mercier & Vilotte, 1993). Furthermore, in cattle and goat CSN1S1 and CSN2 are convergently transcribed (Leroux & Martin, 1996; Rijnkles et al. 1997) and are only 20 and 12 kb apart, respectively.

Structural features of a peptide corresponding to human κ-casein residues 84-101 by 1H-nuclear magnetic resonance spectroscopy

March 1999


27 Reads

The peptide Val-Arg-Arg-Pro-Asn-Leu-His-Pro-Ser-Phe-Ile-Ala-Ile-Pro-Pro- Lys-Lys-Ile, which corresponds to residues 84-101 of human kappa-casein, has been synthesized and its conformation preferences determined by 1H-nuclear magnetic resonance spectroscopy in dimethyl sulphoxide. The peptide adopted a largely extended chain conformation in solution and there was evidence for the presence of a beta-turn involving residues Pro87-His90 of human kappa-casein. The presence of a turn in this position would make the physiologically significant Arg85 residue of human kappa-casein (which is equivalent to Arg97 in bovine kappa-casein) unavailable for interaction with Asp249 of bovine chymosin, and may partly explain why human kappa-casein is hydrolysed more slowly than its bovine counterpart by bovine chymosin.

Isomerisation of cis-9 trans-11 conjugated linoleic acid (CLA) to trans-9 trans-11 CLA during acidic methylation can be avoided by a rapid base catalysed methylation of milk fat

September 2008


33 Reads

This study investigated the evolution of trans-9 trans-11 conjugated linoleic acid (CLA) from cis-9 trans-11 CLA during methylation and its avoidance through a rapid base methylation of milk fat. The study examined three conditions shown to result in loss of cis-9 trans-11 CLA during methylation namely: temperature, methylation time, water contamination in old reagents and acidic conditions. Three techniques currently used for the conversion of milk fat into fatty acid methyl esters for analysis of CLA content by gas liquid chromatography and a fourth procedure designed to eliminate acidic conditions and to limit methylation temperature and time were used. The four methods were: (i) acidic methylation (AM); (ii) acidic and basic bimethylation with fresh reagents (FBM); (iii) acidic and basic bimethylation with pre-prepared reagents (PBM) and (iv) basic methylation (BM). Each regime was carried out on six milk samples over two periods and methylated 1 ml freeze-dried milk (n=12 per regime). Total CLA was not different across methylation regimes (0.30 mg/ml). Isomer cis-9 trans-11 was higher (P<0.01) with BM than the other regimes and lowest with AM: 21.2, 17.8, 18.8 and 14.7 mg/100 ml for BM, FBM, PBM and AM, respectively. The inverse relationship was shown for trans-9 trans-11 with higher (P<0.001) amounts with AM than the other regimes and lowest with BM: 0.57, 2.55, 2.36 and 3.69 mg/100 ml for BM, FBM, PBM and AM, respectively. The trans-10 cis-12 isomer was also shown to alter with methylation procedure being higher (P<0.001) with AM than the other regimes: 0.43, 0.47, 0.29 and 1.20 mg/100 ml for BM, FBM, PBM and AM, respectively. Validation with known CLA free fatty acid and triacylglycerol standards confirmed that AM resulted in conversion of cis-9 trans-11 to trans-9 trans-11, and also elevated trans-10 cis-12 whilst BM of triacylglycerol CLA did not isomerise cis-9 trans-11 and was comparable to FBM.

Effect of psychrotrophic post-pasteurization contamination on the keeping quality at 11 and 5 °C of HTST-pasteurized milk in the UK

December 1982


28 Reads

The keeping quality of commercial HTST-pasteurized milk and laboratory pasteurized milk from a common bulk raw supply has been investigated for 5 dairies. Spoilage occurred at levels of total bacterial counts around 10(7) colony forming units/ml, but with a slightly higher off-flavour threshold for the commercial milks than the laboratory pasteurized milks. The predominant microflora at spoilage and the type of off-flavour produced differed between the 2 types of milk. Raising the storage temperature from 5 to 11 degrees C caused a slight shift in the spoilage microflora and led to an average reduction in the shelf life of the laboratory pasteurized milk from 28 to 6 d and of the commercial pasteurized milk from 13 to 5 d. Changes in the level of post-pasteurization contamination (PPC) were reflected in changes in keeping quality, particularly at 5 degrees C. However, the greatest improvements were found in the absence of PPC.

Restrained molecular dynamics study of the interaction between bovine kappa-casein peptide 98-111 and bovine chymosin and porcine pepsin

September 1995


56 Reads

The cleavage of bovine kappa-casein at the Phe105-Met106 bond by chymosin or pepsin is the first stage in casein micelle coagulation and casein digestion. The nature of the interaction of the peptide His98-Pro-His-Pro-His-Leu-Ser-Phe105-Met-Ala-Ile-Pro-Pro- Lys111 with chymosin and porcine pepsin was investigated using molecular modelling and energy minimization techniques. This study verified and extended a proposed model that electrostatic binding (involving His98, His100, His102 and Lys111 or Lys112) at either end of the active site cleft of chymosin is important for the positioning of residues 103-108 in the cleft. The peptide conformation remained unchanged in going from solution to binding into the active site cleft, with the exception that optimum binding of substrate to chymosin required the isomerization of the His98-Pro99 peptide bond from the trans to the cis conformation. The study also identified an acidic region in porcine pepsin that is in a position to form strong electrostatic interactions with the histidines at the N-terminus of the peptide.

Fig. 1. Total viable count (TVC), Pseudomonas spp count (PSC) and Enterobacteriaceae count (ENC) in raw bovine milk (control) as supplemented with 0·5% (w/v) 7S and 11S soy globulin and kept at 4 °C for 30 d or at 25 °C for 48 h.
Fig. 3. Development of titratable acidity (% lactic acid) and lactose consumption in raw bovine milk during 30 d storage at 4 °C or 48 h at 25 °C, as supplemented with 0·5% (w/v) 7S and 11S globulin.
Fig. 4. Electrophoretic patterns of bovine milk (control) as supplemented with 0·5% (w/v) 7S and 11S soy globulin and kept at 4 °C for 16 d or at 25 °C for 48 h. 
Preservative action of 11S (glycinin) and 7S (β-conglycinin) soy globulin on bovine raw milk stored either at 4 or 25 °C

March 2013


257 Reads

Considerable inhibitory antibacterial actions were exerted by the soybean 11S subunit comparable with nisin on the proliferation of total viable count, Pseudomonas count and Enterobacteriaceae count in bovine milk stored at 4 or 25 °C for 30 d and 48 h, while 7S and lysozyme were much less effective. The maximum magnitudes of bacterial reduction by 11S and nisin were in the range 2-4 log CFU/ml. The proliferation of 3 pathogenic bacteria (Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7) artificially inoculated into raw milk stored at 4 or 25 °C were particularly and significantly (P<0·05) reduced by 11S subunit and nisin (0·5% w/v), but only slightly by 7S and moderately by lysozyme. Lactose consumption, acidity development and casein degradation during storage of bovine raw milk were attenuated during storage at 4 or 25 °C and sensorial traits were better maintained by supplementation with 11S (0·5% w/v). 11S subunit may be used a safely food preservative, if permitted.

Beta-Casein(94-123)-derived peptides differently modulate production of mucins in intestinal goblet cells

October 2014


125 Reads

We recently reported the identification of a peptide from yoghurts with promising potential for intestinal health: the sequence (94-123) of bovine β-casein. This peptide, composed of 30 amino acid residues, maintains intestinal homoeostasis through production of the secreted mucin MUC2 and of the transmembrane-associated mucin MUC4. Our study aimed to search for the minimal sequence responsible for the biological activity of β-CN(94-123) by using several strategies based on (i) known bioactive peptides encrypted in β-CN(94-123), (ii) in silico prediction of peptides reactivity and (iii) digestion of β-CN(94-123) by enzymes of intestinal brush border membranes. The revealed sequences were tested in vitro on human intestinal mucus-producing HT29-MTX cells. We demonstrated that β-CN(108-113) (an ACE-inhibitory peptide) and β-CN(114-119) (an opioid peptide named neocasomorphin-6) up-regulated MUC4 expression whereas levels of the secreted mucins MUC2 and MUC5AC remained unchanged. The digestion of β-CN(94-123) by intestinal enzymes showed that the peptides β-CN(94-108) and β-CN(117-123) were present throughout 1·5 to 3 h of digestion, respectively. These two peptides raised MUC5AC expression while β-CN(117-123) also induced a decrease in the level of MUC2 mRNA and protein. In addition, this inhibitory effect was reproduced in airway epithelial cells. In conclusion, β-CN(94-123) is a multifunctional molecule but only the sequence of 30 amino acids has a stimulating effect on the production of MUC2, a crucial factor of intestinal protection.

Solution conformation of a peptide corresponding to bovine κ-casein B residues 130–153 by circular dichroism spectroscopy and 1H-nuclear magnetic resonance spectroscopy

September 1997


21 Reads

The peptide Pro130-Thr-Ser-Thr-Pro-Thr-Ile-Glu-Ala-Val-Glu140- Ser-Thr-Val-Ala-Thr-Leu-GLu-Ala-Ser-Pro150-Glu-Val-Ile, which corresponds to residues 130-150 of kappa-casein B, was synthesized and the conformation of the peptide in solution investigated by circular dichroism (CD) spectroscopy, structure prediction algorithms and 1H-nuclear magnetic resonance spectroscopy. In a solution containing the structure-enhancing solvent trifluoroethanol the CD spectrum was typical of a peptide in the alpha-helical conformation and nuclear magnetic resonance showed that the amino acids between Ile136 and Ser149 (kappa-casein numbering) were predominantly in the alpha-helical conformation but that Pro130 to Thr135 and Pro150 to Ile153 were not. In addition, Thr133-Pro134 and Ser-149-Pro150 were primarily in the trans conformation, the residues from Thr131 to Thr135 were in unordered structures and the residues from Glu151 to Ile153 were in an extended conformation. Residues Glu137 to Glu140 and Thr145 to Ala148 also displayed some 3(10)-helix character. When the peptide was dissolved in 10 mM-cetyltrimethylammonium chloride solution at pH 6, the CD spectra indicated that the proportion of helical structure was comparable to that of the peptide in trifluoroethanol solution (400 ml/l), whereas when the peptide was dissolved in buffer alone in 10 mM-SDS solution, the CD spectra were consistent with a low helical content. Acidification of these solutions to pH 2.85 resulted in a slight increase in the helical content of the peptide in buffer and more markedly in buffer containing SDS. When the peptide was in 5 mM-CaCl2 solution at neutral pH, the CD spectrum indicated that some ordered structure was present. Taken together these results indicate that the ionizable residues Glu137, Glu140, Glu147 and Glu151 could be important in determining the stability of the putative helix. The structure predictions found that the sequence from Glu137 to Pro150 would be more likely to be in a helical than any other conformation in the intact bovine protein, but that pig, sheep and goat kappa-caseins did not give a prediction of a strongly helical region in this part of the molecule.

Fig. 1. Newly identified SNPs in the bovine SLC27A1 gene by sequencing all the exons and flanking introns. Each SNP was assigned to its position in the reference sequence (AAFC03051286) taking into consideration that the gene is coded in the complementary sense. Also a correlative number was given to each of them. 
Fig. 2. Allele frequencies of the SLC27A1 SNPs (numbered from 1 to 14 according to Fig. 1) in the tails of Holstein-Friesian animals with highest (H) and lowest (L) EBV for milk fat content. For each SNP, bars correspond to frequencies of allele 1 (white) and allele 2 (black). Also the value of allele 1 frequency (p) is indicated below for the high and low Holstein-Friesian groups and the Asturiana de los Valles (p A ) and Menorquina (p M ) breeds. 
Identification of 14 new single nucleotide polymorphisms in the bovine SLC27A1 gene and evaluation of their association with milk fat content

June 2008


88 Reads

The solute carrier family 27 member 1 (SLC27A1) is an integral membrane protein involved in the transport of long-chain fatty acids across the plasma membrane. This protein has been implicated in diet-induced obesity and is thought to be important in the control of energy homeostasis. In previous reports, our group described the isolation and characterization of the bovine SLC27A1 gene. The bovine gene is organized in 13 exons spanning over more than 40 kb of genomic DNA and maps in BTA 7 where several quantitative trait loci for fat related traits have been described. Because of its key role in lipid metabolism and its genomic localization, in the present work the search for variability in the bovine SLC27A1 gene was carried out with the aim of evaluating its potential association with milk fat content in dairy cattle. By sequencing analysis of all exons and flanking regions 14 new single nucleotide polymorphisms (SNPs) were identified: 1 in the promoter, 7 in introns and 6 in exons. Allele frequencies of all the SNPs were calculated by minisequencing analysis in two groups of Holstein-Friesian animals with highest and lowest milk-fat content estimated breeding values as well as in animals of two Spanish cattle breeds, Asturiana de los Valles and Menorquina. In the conditions assayed, no significant differences between Holstein-Friesian groups were found for any of the SNPs, suggesting that the SLC27A1 gene may have a poor or null effect on milk fat content. In Asturiana and Menorquina breeds all the positions were polymorphic with the exception of SNPs 1 and 8 in which C allele was fixed in both of them.

Monospecificity of the antibodies to bovine alpha s1-casein fragment 140-149: application to the detection of bovine milk in caprine dairy products

March 1995


16 Reads

Comparison of the primary sequences of bovine, ovine and caprine alpha s1-casein shows a deletion of eight amino acid residues in the ovine casein region 141-148, which is identical in the bovine and caprine proteins except for a single difference in position 148 (Q or E). Polyclonal antibodies raised in rabbits against the bovine casein sequence 140-149 (QELAYFYPEL) appeared monospecific for bovine alpha s1-casein, since no antibody-antigen complex was formed with homologous ovine or caprine proteins. These antibodies remained unable to recognize the caprine sequence in the native protein even after extensive tryptic proteolysis. The lack of immunoreactivity of the antibodies against synthetic caprine alpha s1-casein peptide 138-149 (VNQELAYFYPQL) suggested that the glutamic acid residue in position 148 is essential for the antigenic character of the bovine peptide. From these observations, the use of these antibodies for the detection and quantitation of bovine milk present in ovine dairy products could be extended to caprine products.

Synthesis, effectiveness and metabolic fate in cows of the caesium complexing compound ammonium ferric hexacyanoferrate labelled with 14C

March 1988


72 Reads

Adding ammonium ferric hexacyanoferrate (AFCF) to cows' fodder produced after the Chernobyl nuclear accident prevented milk contamination by increasing the faecal elimination of 137Cs. Synthesis of ammonium ferric hexa[14C]-cyanoferrate (AF14CF) and its purification were performed for the study of the metabolic fate of this complex, and the evaluation of the possible release of cyanide. The stability of this colloidal product, tested by anaerobic incubation in rumen juice in vitro, showed no release of free cyanide from AF14CF, but hexacyanoferrate was identified in the rumen juice and 0.13% of the added radioactivity was converted to labelled CO2. AF14CF administered per os to two cows showed a nearly quantitative excretion of radioactivity in faeces during the first 3 d (91-95%). A very low but significant level of radioactivity appeared in plasma, blood cells, expired CO2 and was detected in organs taken 9 d after administration. Total cumulative radioactivity in urine and milk amounted to 0.19-0.47% and 0.068-0.071% respectively for the two cows. Labelled hexacyanoferrate and thiocyanate were identified in the urine and also in faeces. In spite of this relative instability of AFCF in the rumen of cows, the poor absorption of AF14CF degradation products showed that AFCF constitutes an efficient and safe food additive to prevent the absorption of radioactive caesium from ruminant feed and its secretion in milk.

Metabolism of [U-14C; 2,3-3H]-L-valine by the isolated perfused goat udder

February 1979


9 Reads

Two lactating mammary glands excised from 2 goats were perfused for several hours in the presence of [U-14C; 2,3-3H]-L-valine and received adequate quantities of glucose, acetate and amino acids. In the synthesized milk 96 and 89% respectively of the casein valine was derived from free plasma valine. Valine was extensively catabolized by mammary tissue, resulting in a considerable 14CO2 production and in the incorporation of 14C into milk citric acid and to a lesser extent into casein aspartic acid and glutamic acid. About 30% of the valine molecules which were taken up by the mammary gland were oxidized to CO2 and 70% were incorporated in casein as valine residues. About 10% of the plasma valine molecules were reversibly transaminated during one passage through the udder. An important amount of radioactivity of plasma was present in unknown metabolites. Only 7% of this activity was localized in isobutyrate. The radioactivity of total milk fat was very low. Mainly iso-14:0, iso-16:0 and 15:0 were labelled.

The metabolism of [14C]bicarbonate by Streptococcus lactis: the synthesis of succinic acid

November 1978


10 Reads

Whole cells of Streptococcus lactis C10, when incubated with an energy source, converted fumarate to succinate and malate to lactate. Cell-free extracts of Str. lactis C10 contained fumarate reductase, but no aspartase, adenylosuccinate synthetase and lyase or argininosuccinate synthetase and lyase activity could be detected. Cells grown in the presence of [14C]bicarbonate produced labelled succinate during the synthesis of purine bases. However, the amount of succinate produced by this pathway only accounted for approximately one-sixth of the succinate produced by the cells.

The metabolism of [14C]bicarbonate by Streptococcus lactis: the fixation of [14C]bicarbonate by pyruvate carboxylase

November 1978


7 Reads

The fixation of [14C]bicarbonate into aspartate by Streptococcus lactis C10 was achieved by the combined reactions of pyruvate carboxylase (E.C. and glutamate-oxaloacetate transaminase (E.C. The pyruvate carboxylase from Str. lactis C10, which was most active at pH 8.0, was activated by the divalent metal ions Mn2+, Mg2+ and Co2+, and inhibited by sulphydryl reagents. The enzyme was inhibited non-competitively by aspartic acid and competitively by oxaloacetate.

Identification of a single nucleotide polymorphism at intron 16 of the caprine Acyl-Coenzyme A: Diacylglycerol acyltransferase 1 (DGAT1) gene

March 2007


205 Reads

The DGAT1 gene encodes a microsomal enzyme that catalyses the only committed step in triacylglycerol synthesis by joining diacylglycerol and fatty acyl coenzyme A. In cattle, a K232A substitution in the DGAT1 molecule has a significant effect on enzyme activity and milk fat content. The prominent role of this gene in lipid metabolism led us to undertake the structural characterization of DGAT1 in goats. In this way, we have sequenced a 1552 bp fragment of the goat DGAT1 cDNA, which encompasses most of the coding sequence (from exon 1 to 17), and a genomic fragment covering exons 12 to 17. Multiple alignment of the goat DGAT1 sequences revealed the existence of a single nucleotide polymorphism (SNP) involving a T to C substitution at intron 16. We optimized a primer extension based genotyping method that allowed us to determine that the C variant is a minority allele with frequencies ranging from 0.062 (Murciano-Granadina) to 0.109 (Malagueña). This SNP, although not expected to have any functional effect, might be useful as a genetic marker in association studies to detect additional DGAT1 polymorphisms which might influence fat milk content and other traits of economic interest.

Molecular methods for identification of Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus using methionine biosynthesis and 16S rRNA genes

August 2008


185 Reads

Yoghurt and starter culture producers are still searching strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus to produce healthier yogurt with longer shelf life, better texture, taste and quality. However, selective identification of Lb. delbrueckii subsp. bulgaricus and Strep. thermophilus from a mixed population using microbiological and biochemical methods is difficult, time consuming and may not be accurate. In this study, a quick, sensitive and accurate method is proposed to identify both Lb. delbrueckii subsp. bulgaricus and Strep. thermophilus using PCR. The method is comprised of two parts. In the first part, methionine biosynthesis genes, known to be present in both species were partially amplified by designed primers (cysmet2F and cysmet2R). Partial amplification of the methionine biosynthesis gene which gives 700 bp fragment resulted in selective identification of Lb. bulgaricus and Strep. thermophilus. All 16 Lb. bulgaricus and 6 Strep. thermophilus isolates assessed by this method gave the expected amplification. On the other hand, further analysis of other closely related species with the same primers have indicated that the same product was also amplified in two more lactobacilli namely, Lb. delbrueckii subsp. lactis and Lb. helveticus species. Thus, in the second part of the method, further differentiation of Lb. delbrueckii subsp. bulgaricus and Strep. thermophilus from each other and these species was achieved using restriction analysis of 16S rRNA gene with EcoRI.

Resistance of 17 mesophilic lactic Streptococcus bacteriophages to pasteurization and spray-drying

March 1980


33 Reads

For 17 phages active against Streptococcus cremoris, Str. lactis and Str. lactis subsp. diacetylactis, the killing efficiency of pasteurization (log No/N) at 72 degrees C for 15 s in skim-milk showed large variations from greater than 6 to 0; the efficienty of killing during spray-drying ranged from 3.7 to 0.2 and phages survived well storage of milk powder at room temperature. Destruction in a heat exchanger was found to be greater than that calculated from biphasic curves obtained by heating phages in sealed ampoules. No relationship was established between lytic classification of phages and their heat resistance.

Fig. 1. High resolution optical microscopy showing haematoxylin and eosin stained from representative epithelial tissue sample of bovine mammary gland canal after intrammamary inoculation with Lactobacillus perolens CRL 1724. (a) and (b) non-inoculated with Lb. perolens CRL 1724. Presence of keratin superficial layer (K) and connective tissue with presence of empty blood vessel (black arrow) (20 × and 40, respectively). (c) and (d) epithelial tissue samples and connective tissue from inoculated quarter without change compared with controls (20 × and 40, respectively). The bar in each panel is equivalent to 10 μ M . 
Fig. 2. High resolution optical microscope photographs showing haematoxylin and eosin stained from representative epithelial tissue sample of bovine mammary gland cistern after intrammamary inoculation with Lactobacillus perolens CRL 1724. (a) non-inoculated (100 ×). (b), (c) and (d) epithelial tissue of inoculated quarter. (b) and (c) presence of neutrophils near to the epithelial zone (black arrows) (100 ×). (d) bacterial adhered to the surface of epithelial tissue (greys arrows) (100 ×). The bar in each panel is equivalent to 10 μ M . 
Fig. 3. Transmission electron micrographs showing representative sample of teat canal epithelial cells after intrammamary inoculation with Lactobacillus perolens CRL 1724 (a) non-inoculated, nucleus (n), nucleolus (white arrows) and nuclear membrane (black arrows) of epithelial cells (4000 ×). (b) epithelial cells of inoculated quarter with nucleus (n), nucleolus (white arrows) and membrane nuclear (black arrows) without modifications (6000 ×). (K): Keratin. 
Fig. 4. High resolution optical microscope photographs showing toluidine blue stained of representative sample of tissue cells of bovine mammary gland cistern after intrammamary inoculation with Lactobacillus perolens CRL 1724. (a) non-inoculated, mammary cells (black arrows) and blood vessel with scarce presence of blood cells (white arrow) (100 ×). (b) mammary tissue cells of inoculated quarter without morphological modifications in nucleus, nucleolus or membrane nuclear (black arrows); full blood vessel (white arrow) (100 ×). The bar in each panel is equivalent to 10 μ M . 
Histological examination of non-lactating bovine udders inoculated with Lactobacillus perolens CRL 1724

November 2012


394 Reads

The effect of intramammary inoculation of Lactobacillus perolens CRL 1724 on bovine udders at drying off was evaluated through histological examination of the canal and cistern tissues. The persistence of the strain in the udder 7 d post inoculation was also determined. Lb. perolens CRL 1724 was recovered from all mammary quarters and no clinical signs or teat damage were observed after inoculation of 106 cfu/ml. The udders showed a normal structural aspect and there were no modifications of the milk appearance. Lb. perolens CRL 1724 cells were evidenced on the surface of the epithelial cells of the cistern without causing any morphological modifications or cell alterations. Lb. perolens CRL 1724 produces a mild inflammatory reaction, characterized by recruitment of neutrophils to the epithelial zone and a slight hyperaemia into blood vessels. This preliminary study provides important information for further studies directed towards the inclusion of Lb. perolens CRL 1724 in the design of probiotic products for preventing bovine mastitis in non-lactating dairy cows.

Technological characterization and survival of the exopolysaccharide-producing strain Lactobacillus delbrueckii subsp lactis 193 and its bile-resistant derivative 193+in simulated gastric and intestinal juices

August 2011


143 Reads

The capacity of lactic acid bacteria to produce exopolysaccharides (EPS) conferring microorganisms a ropy phenotype could be an interesting feature from a technological point of view. Progressive adaptation to bile salts might render some lactobacilli able to overcome physiological gut barriers but could also modify functional properties of the strain, including the production of EPS. In this work some technological properties and the survival ability in simulated gastrointestinal conditions of Lactobacillus delbrueckii subsp. lactis 193, and Lb. delbrueckii subsp. lactis 193+, a strain with stable bile-resistant phenotype derived thereof, were characterized in milk in order to know whether the acquisition of resistance to bile could modify some characteristics of the microorganism. Both strains were able to grow and acidify milk similarly; however the production of ethanol increased at the expense of the aroma compound acetaldehyde in milk fermented by the strain 193+, with respect to milk fermented by the strain 193. Both microorganisms produced a heteropolysaccharide composed of glucose and galactose, and were able to increase the viscosity of fermented milks. In spite of the higher production yield of EPS by the bile-resistant strain 193+, it displayed a lower ability to increase viscosity than Lb. delbrueckii subsp. lactis 193. Milk increased survival in simulated gastric juice; the presence of bile improved adhesion to the intestinal cell line HT29-MTX in both strains. However, the acquisition of a stable resistance phenotype did not improve survival in simulated gastric and intestinal conditions or the adhesion to the intestinal cell line HT29-MTX. Thus, Lb. delbrueckii subsp. lactis 193 presents suitable technological properties for the manufacture of fermented dairy products; the acquisition of a stable bile-resistant phenotype modified some properties of the microorganism. This suggests that the possible use of bile-resistant derivative strains should be carefully evaluated in each specific application considering the influence that the acquisition of a stable bile-resistant phenotype could have in survival ability in gastric and intestinal conditions and in technological properties.

A 1H-NMR study of bovine casein micelles; influence of pH, temperature and calcium ions on micellar structure

February 1989


26 Reads

The influence of pH, temperature and Ca depletion on bovine casein micelle suspensions in D 2 O containing simulated milk ultrafiltrate was studied by ¹ H-NMR spectroscopy. In the pH range of 5·8–7·5 the spectrum of the micelles showed very little pH dependence, indicating that no changes occurred in the dynamic behaviour of the proteins constituting the micelle. The NMR spectrum of casein micelles was strongly temperature dependent, particularly in the temperature range of 60–98 °C. Increase in temperature resulted in a strong increase in spectral intensity concomitant with changes in the spectral characteristics. In micelle suspensions these changes were reversible, and indicated that at clevated temperatures the rigid structure of the casein micelle started to melt, leading to an increased mobility of appreciable parts of the proteins in the micelle. Ca depletion of the casein micelles by addition of EDTA resulted in an increase in spectral intensity, which arose from the presence of casein components in the serum phase, The spectrum of these serum phase particlcs resembled closely the spectrum of a solution of total casein in simulated milk ultrafiltrate and was quite different from the spectrum of casein micelles. The implications of these results with respect to models of the structure of bovine casein micelles are discussed.

Structural features of bovine caseinomacropeptide A and B by 1H nuclear magnetic resonance spectroscopy

March 2002


64 Reads

Samples of bovine caseinomacropeptide (CMP) were isolated from kappa-casein A and kappa-casein B and fractionated to give aglycosylated CMP A and CMP B and monoglycosylated CMP A. The secondary structures of these three peptides were compared under neutral and acidic (pH 4.2) conditions, using two-dimensional (2D) 1H nuclear magnetic resonance (NMR) spectroscopy. The differences between the spectra at pH 4.2 and 7.0 and the spectra of the aglycosylated and glycosylated CMP A were subtle, indicating little change in backbone conformation with these changes. These results Suggest that differences in the coagulation properties of milks containing either kappa-casein A or kappa-casein B are more likely to be related to factors, such as micelle size or charge, than to structural differences arising from altered backbone conformation of the macropeptide segments of the kappa-caseins.

Lactobacillus reuteri DSM 20016: purification and characterization of a cystathionine gamma-lyase and use as adjunct starter in cheesemaking

June 2002


69 Reads

A homo-tetrameric [similar]160-kDa cystathionine γ-lyase was purified to homogeneity from Lactobacillus reuteri DSM 20016 by four chromatographic steps. The activity was pyridoxal-5′-phosphate dependent and the enzyme catalyzed the α,γ-elimination reaction of L-cystathionine, producing L-cysteine, ammonia and α-ketobutyrate. The enzyme was active towards a range of amino acids and amino acid derivatives, including methionine. The pH and temperature optima were found to be 8.0 and 35 °C, respectively. Isoelectric pH (pI) was [similar]5.0 as determined by two-dimensional electrophoresis. Sensitivity to chemical inhibitors was typical of lactococcal cystathionine γ- and β-lyases, except it was inhibited by sulphydryl reagents. The N-terminal sequence was MKFNTQLIHGGNSED, which had 100% homology with cystathionine β-lyase of Lb. reuteri 104R (Accession Number CAC05298). Lb. reuteri DSM 20016, together with 10 other strains of non-starter lactic acid bacteria, was used as adjunct starter in the production of miniature Canestrato Pugliese-like cheeses. After 40 d ripening, the water-soluble extract of the cheeses with added Lactobacillus fermentum DT41 and Lb. reuteri DSM 20016 contained the highest enzyme activities on cystathionine and methionine substrates. Determinations of methanethiol, dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide in the miniature cheeses confirmed the findings of enzyme activities.

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