One of the major concerns associated with human dietetics is the deficiency of protein content in the provided diet. It is also a common thing to notice that even though a good source of proteinaceous content is supplied through proper diet supplements, the host body is unable to convert them into proper absorbable form. As a result the body suffers from the basic building blocks the amino acids. A number of bacteria have been identified with higher efficiency of breaking down the protein content of our diet into the forms that are required for the growth, development, repair and regeneration of the body. Quite a few of the probiotic bacteria have been assessed for their protein hydrolyzing capabilities and the subsequent release of essential amino acids into the host body.
A good number of Lactobacillus species have been known to hydrolyze the milk casein and extract good nutritional value out of the fermented milk product. They are known to possess various cellular peptidases as well as proteinases, the enzymes required to bring about the fruitful metabolism of the protein of milk origin. There is very little knowledge available regarding the proteolytic ability of the probiotic bacteria from the genus Enterococcus.
However the strains from this genus are potent protein metabolizing agents. The first such report regarding the proteolytic activity of Enterococcus was made as early in the late 60s. In that study performed by Somkuti et al., it was found that the E. faecalis strain liquefaciens possess an extracellular protein degrading enzyme which could specifically hydrolyze casein. Later on, E. durans was also added to this list of protease producing strains. In addition to its ability to break down casein it was also able to metabolize h-lactoglobulin another of the milk proteins.
Later studies suggest that the efficiency of the Enterococcus strains to hydrolyze milk protein was dependent on the strain type chosen as well as the exposure time. In vitro studies have supported such claims which have shown that E. faecalis strains were more potent degrader of casein during the first 48 hours of their incubation in milk but not so at around 120 hours. Later on a strain of E. faecalis was identified that possessed the proteinases to breakdown h-lactoglobulin, α-lactalbumin and casein with similar efficiency. It is also evident from a multitude of research works that strains belonging to E. faecalis possessed greater proteolytic potential as compared to the strains from the E. faecium.
The strains of Lactobacillus genus have in their repertoire some excellent proteolytic enzymes that results in the production of peptides during the fermentation of milk that are biologically active and more bioavailable. The biologically active peptides have been associated with the inhibitory role against bacterial pathogenic peptides and other antagonistic peptides regarded as harmful for the human health. Some of the useful strains of this genus belong to the species like L. helveticus, L. delbrueckii, L. bulgaricus, L. lactis Cremoris and so on. Their effective mode of proteolytic activity can be applied in the regulation of blood pressure via the inhibition of enzyme required for Angiotensin-I conversion. As such these Lactobacillus strains have been associated with the maintenance of overall improved state of human physiological processes.
Recently an insight into the proteolytic activity of the Lactobacillus strains was found with the published result in the journal, Applied and Environmental Microbiology. In that study, it was found that the strains of Lactobacillus helveticus synthesize some proteinases of the cell wall that are involved in the proteolytic activities. The simultaneous expression of the two genes PrtH and PrtH2 was responsible for a greater degree of amino acid release from the substrates. As such the genes were associated with the better utilizing efficiency of the milk casein.
Strains isolated from Streptococcus thermophilus showed effectiveness in the utilization of the vegetable based proteins. They showed better activities of the break down of the proteins. In a study carried out by the group of Donkar et al., it showed that the Streptococcus strains were involved in the release of essential amino acids from fermented soymilk. Anti-ACE activities were also associated with the proteolytic cleavage of the proteins. It was also found that the probiotic strains from this group released bioactive peptides and that it was directly proportional to the specific strains as well as the time of their action on the substrates.
The Bifidobacterium bacterial strains either applied directly or through the fermented food products have shown increased bioavailability of amino acids and dipeptides. In particular they possess not only the proteinase activities to hydrolyze the proteins but also the peptidase of different types and of varied degrees to break down the amino acids into singular forms. Accordingly, the strains from B. breve were studied for these activities and some remarkable data came into the forth.
These probiotic bacterial strains possessed increased aminopeptidase activities. In addition, they had dipeptidase and tripeptidase activities that could breakdown the peptides of lengths two and three amino acids to bring them down to the basic constituent of the proteins. Besides, the beneficial bacteria from this genus possessed both intracellular as well as extracellular proteinase activities. There are also reports for their usefulness in the effective modulation of the protein metabolism in the colon. Oral administration of the strains of B. longum have resulted in the excretion of indoxyl sulfate which is the end product of metabolism of the essential amino acid tryptophan thereby suggesting a role for them even in the amino acid metabolism.
There are ever expanding evidences for the effectiveness of the application of the probiotic bacteria in the metabolism of proteins due to their higher efficiency to hydrolyze some proteins in a much better way than the human beings. The specific strains from the different genera of the probiotic bacteria can be applied for the release of absorbable amino acids from the proteins used as dietary supplements. Their effectiveness in this regard can alleviate a number of disorders that occurs due to protein deficiency.