Abstract
Lactobacillus helveticus is one of the species of lactic acid bacteria (LAB) most commonly used in the production of fermented milk beverages and some types of hard cheese. The versatile nature of this bacterium is based on its highly efficient proteolytic system consisting of cell-envelope proteinases (CEPs), transport system and intracellular peptidases. Besides use of L. helveticus in cheese processing, the production of fermented milk preparations with health promoting properties has become an important industrial application. Studies have shown that fermented dairy products are able to decrease blood pressure, stimulate the immune system, promote calcium absorption, and exert an anti-virulent effect against pathogens. These beneficial effects are produced by a variety of peptides released during the hydrolysis of milk proteins by the proteolytic system of L. helveticus, which provides the bacterium with its nutritional requirements for growth. In recent years, studies have focused on understanding the factors that affect the kinetics of milk protein hydrolysis by specific strains and have concentrated on the effect of pH, temperature, growth phase, and matrix composition on the bacterial enzymatic system. This review focuses on the role of the proteolytic system of L. helveticus in the production of bioactive compounds formed during fermentation of dairy products. Taking advantage of the powerful proteolytic system of this bacterium opens up future opportunities to search for novel food-derived compounds with potential health promoting properties.
Highlights
Lactobacillus helveticus is a homofermentative, thermophilic lactic acid bacterium widely used in the manufacture of Swiss type and, Italian aged cheeses, and fermented milk drinks (Gatti et al, 2004; Vinderola et al, 2007a)
The industrial importance of L. helveticus depends on its effective proteolytic system, which seems to be the most efficient between lactic acid bacteria (LAB), as well as the specificity of different strains
Little is known regarding the specificity of the cell-envelope proteinases (CEPs) on caseins, the transport system of the peptides, and the factors that can affect both the individual components of the system and the proteolytic system as a whole
Summary
Lactobacillus helveticus is a homofermentative, thermophilic lactic acid bacterium widely used in the manufacture of Swiss type and, Italian aged cheeses, and fermented milk drinks (Gatti et al, 2004; Vinderola et al, 2007a). During milk fermentation only 1–2% of milk proteins undergo proteolysis and the principal substrate is casein but limited degradation of whey proteins may occur (Khalid et al, 1991; Szwajkowska et al, 2011) The effect of this proteolysis is that fermented milks have a higher content of peptides and free amino acids, especially valine, histidine, serine and proline, than non-fermented milk (Matar et al, 2003). In order to assure its nutritional requirements when grown in milk, L. helveticus counts on a potent proteolytic system capable of producing short peptides and liberating amino acids from the casein matrix. This explains why it has higher proteolytic activity than most other lactobacilli and why it hydrolyses more casein in culture media than other species (Savijoki et al, 2006). The proteolytic system of L. helveticus and the majority of LAB consists of proteinases which initially cleave caseins to large peptides, peptidases (intracellular), which further degrade these peptides to small peptides and amino acids, and specific transport proteins which transport amino acids and peptides across the cytoplasmic membrane (Kenny et al, 2003)
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