Suman Singh
Kurukshetra University
India
Title: Studies of probiotic attributes and membrane proteins of Pediococcus acidilactici: A facultative anaerobe with great probiotic potential
Biography
Biography: Suman Singh
Abstract
Lactic acid bacteria (LAB) are generally regarded as safe (GRAS) and being widely used as probiotics. Pedicoccus acidilactici is a LAB with advantage of being facultative anaerobe, non pathogenic and of dairy origin. In vitro studies confirmed the essential basic probiotic properties viz., bile salt tolerance and percent hydrophobicity. Antioxidant activity, wide spectrum of proteolytic activities and β-galactosidase activity are promising for conferring health benefits. Its resistance to lysozyme suggests it to be a useful strain for infants and newborns being fed on mother’s milk. β-galactosidase activity and lactic acid production by P. acidilactici also confer industrial significance to the strain in addition to probiotic attributes. Genome studies of P. acidilactici revealed about 60 unidentified peptidase or protease. Protease, particularly membrane proteases are implicated in bacterial host interaction. Two high molecular weight membranes bound metallo-exopeptidases viz., DPP-III and aminopeptidases were purified from P. acidilactici. DPP-III hydrolyzed Arg-Arg-4mβNA and aminopeptidase B hydrolyzed Arg-4 mβNA. DPP-III worked optimally at pH 8.5 and 37o C. It was tetrameric with different subunits (Mol wt. 120.24 kDa). It was serine protease, activated by Co2+ and exhibited micromolar affinity (Km 9.1 µM) for its substrate. Aminopeptidase B worked optimally at pH 7.5 and 40o C. It was a heterotrimer of 101.36 kDa. It also exhibited micromolar affinity with Km 26 µM for Arg-4mβNA. It was a thiol protease. Both enzymes are expected to generate bioactive peptides, an important contribution by probiotic bacteria. Extracellular enzymes of probiotic bacteria help host as well as bacteria itself. One extracellular casein hydrolyzing endoprotease was purified from P. acidilactici which had sequence similarity to DING proteins. This enzyme was a monomer of 38.9 kDa and also possessed phosphatase activity. This enzyme was a thiol protease, inhibited by EDTA and stable up to pH 12.0 and 50o C and it was resistant to organic solvents. These studies suggest P. acidilactici to be a potential probiotic for human. Further studies of enzymes will be useful in gaining insight in mechanism of action of this bacteria and thus therapeutic significance. Further studies are in progress for biochemical and molecular characterization of strain.