CHARACTERIZING FAVOURABLE METABOLITES IN PROBIOTIC YOGURT

The bioactivity of fermented milk products has been attributed to bioactive metabolites, mainly short-chain fatty acids (SCFA) and peptides generated during the fermentation process by starter and probiotic species. The SCFA are associated with various bioactivities such as anti-inflammatory, immunomodulatory, and gut barrier strengthening effects. Their production in dairy products during fermentation is influenced by the variability in probiotic strain or species type and metabolic interactions between different species or strains. Milk-derived peptides on the other hand are products of hydrolysis of caseins and whey proteins through the activities of native peptidases and microbial enzymes during fermentation. The bioactivities of these peptides include angiotensin-converting-enzyme (ACE) inhibition, dipeptidyl peptidase IV (DPP-IV) inhibition, antimicrobial, anti-oxidative, antithrombotic, antihypertensive, opioid agonist, mineral binding, and immune-modulatory properties. However, information on the peptide profiles produced in multi-probiotic species yogurt incorporating co-cultures of Bifidobacterium spp. and Lactobacillus rhamnosus is lacking. Therefore, the authors cited hypothesized that the incorporation of L. rhamnosus and Bifidobacterium spp. in yogurt will improve the degree of proteolysis and the diversity of generated peptides and increase bio-functional properties of the peptides and SCFA. This study, therefore, determined the bioactive peptide and SCFA profiles of mixed-species yogurt incorporating Bifidobacterium spp., namely, Bifidobacterium bifidum (B. bifidum) ATCC 11863, Bifidobacterium breve ATCC 15700, and Bifidobacterium animalis ssp. animalis ATCC 25527, and L. rhamnosus GG/ATCC 53103 with the aim of producing probiotic yogurt with enhanced functionality.

The methods employed were respectively ultra-performance liquid chromatography coupled to electrospray ionization quadrupole-time-of-flight MS and GC-MS.

Significantly higher proteolytic activities were observed in yogurt which incorporated either the probiotic species of B. bifidum ATCC 11863 or L. rhamnosus GG. The yogurt which incorporated B. bifidum ATCC 11863 contained more peptides with higher bioactivity. Bifidobacterium animalis ssp. animalis ATCC 25527 significantly enhanced the SCFA content (acetic acid) in yogurt, whereas L. rhamnosus GG increased the production of both bioactive peptides and SCFA in the yogurt when incorporated as a monoculture or co-culture with B. bifidum ATCC 11863 and B. animalis ssp. animalis ATCC 25527, respectively. In addition, novel short peptides (<10 amino acids) derived from minor milk serum proteins with potential antimicrobial properties were also identified in the different probiotic yogurts.

Conclusions: It was found that the profiles of bioactive peptides and SCFA were both influenced by the probiotic species or strain incorporated into the yogurt. B. bifidumATCC 11863 contributed more bioactive peptides either as a mono-probiotic culture or in co-cultures with L. rhamnosus GG in yogurt compared with other Bifidobacterium spp. On the other hand, B. animalis ssp. animalis ATCC 25527 enhanced the acetic acid content in the yogurt either as a mono-probiotic culture or in co-cultures with L. rhamnosus GG. The study further showed that minor milk serum proteins contributed novel short peptides with potential antimicrobial properties. Therefore, the selection of probiotic strains to be incorporated in yogurt is vital for enhanced functionality. This information could be used by the dairy and probiotic industries for the development of novel functional yogurt for health-oriented consumers.