Bile salt hydrolases were purified to electrophoretic homogeneity from Bifidobacterium bifidum ATCC 11863, Bifidobacterium infantis KL412, Bifidobacterium longum ATCC 15708, Bifidobacterium longum KL507, and Bifidobacterium longum KL515. Three different types (A, B, and C) of bile salt hydrolase (BSH) were revealed during the purification study, exhibiting the type-specific characteristics in their electrophoretic migration and elution profiles from anion exchange and hydrophobic interaction chromatographic columns. The subunit molecular mass estimated by sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) was around 35 kDa, and the native molecular mass in all five Bifidobacterium strains was estimated to be between 130 and 150 kDa by gel filtration chromatography, indicating that all BSH enzymes have tetrameric structure. From the isoelectric focusing, an isoelectric point value of 4.45 was obtained with BSH (type B) from B. bifidum ATCC 11863 and the other BSH (types A and C) showed the similar pI values around 4.65. N-Terminal amino acid sequencing for the proteins of types A and C revealed that 6 out of 20 amino acid residues were different, and highly conserved residues were identified in both N-terminal sequences of types A and C. All BSH enzymes from five strains hydrolyzed six major human bile salts, and they showed a better deconjugation rate on glycine-conjugated bile salts than on taurine-conjugated forms.

Antihypertensive peptides inhibiting angiotensin I-converting enzyme have been isolated from enzymatic hydrolysates of various food materials, but no information is available on the isolation of antihypertensive peptides from enzyme-modified cheese. In this study, several bioactive peptides, mainly potential antihypertensive peptides from enzyme-modified cheese prepared by commercial and Lactobacillus casei enzymes, were purified and identified. Enzyme-modified cheese samples were prepared by combination of Neutrase (1883.0 U/ml), L. casei enzymes (amino peptidase activity 86.4 leucine aminopeptidase U/g), and Debitrase (22.0 leucine aminopeptidase U/g). The water-soluble fractions of the enzyme-modified cheeses that were prepared by different enzymes were subjected to reverse-phase HPLC on a Delta Pak C18 column. Each peak was purified on the same column using a binary gradient. One peak from the Neutrase digest, five peaks from the Neutrase-Debitrase digest, and two peaks from the Neutrase-Lactobacillus enzyme digest were purified and identified by API mass spectrometry. On the basis of their molecular masses, amino acid sequences of purified peptides were identified. beta-Casomorphin with a sequence like that of beta-casein (YPFPGPI f 60-66) was found after the Neutrase digest. All of the peptides purified from the digests with combination of Neutrase and Debitrase or Neutrase and L. casei enzymes contained active sites in their sequences. The presence of sites containing potential antihypertensive peptides suggests that the purified peptides may have antihypertensive properties. Thus, the enzyme-modified cheese process, mainly designed to produce flavor ingredients, may simultaneously produce bioactive peptides, which are considered to be of physiological importance.

Aims:  To study the ability of the probiotic culture Lactobacillus acidophilus La‐5 to produce conjugated linoleic acid (CLA), which is a potent anti‐carcinogenic agent. Methods and Results:  The conversion of linoleic acid to CLA was studied both by fermentation in a synthetic medium and by incubation of washed cells. Accumulation of CLA was monitored by gas chromatography analysis of the biomass and supernatants. While the fermentation conditions applied may not be optimal to observe CLA production in growing La‐5 cells, the total CLA surpassed 50% of the original content in the washed cells after 48 h under both aerobic and micro‐aerobic conditions. The restriction of oxygen did not increase the yield, but favoured the formation of trans, trans isomers. Conclusions:  The capability of L. acidophilus La‐5 to produce CLA is not dependant on the presence of milk fat or anaerobic conditions. Regulation of CLA production in this strain needs to be further investigated to exploit the CLA potential in fermented foods. Significance and Impact of the study:  Knowledge gained through the conditions on the accumulation of CLA would provide further insight into the fermentation of probiotic dairy products. The capacity of the nongrowing cells to produce CLA is also of great relevance for the emerging nonfermented probiotic foods.