Exploring the bacterial diversity of and#945;galactosidase producing isolates from hot springs and to study the production purification and characterization of and#945; galactosidase from high yielding isolate

Abstract

and#945;-D-Galactosidases are exoglycosidases, which works by hydrolyzing the terminal and#945;-galactosyl moieties from glycoproteins, oligosaccharides, galactomannans and galactolipids. Transgalactosylation reactions are also catalyzed by the enzyme using numerous substrates (natural and synthetic) transferring the galactose moiety to an acceptor instead of water. Geothermal springs were preferred as the source of thermophilic microorganisms to obtain thermostable enzymes which showed good tolerance to harsh industrial processes especially stability at higher temperatures. In this study, culture independent approach and next generation sequencing was used to analyze bacterial taxonomic and functional (and#945;-galactosidase) diversity of Manikaran hot springs, Himachal Pradesh, India. It revealed presence of dominant phyla/genera in 3 water and 2 soil samples using MG-RAST. A total of 997 bacterial strains were identified using SEED database on the basis of and#945;-galactosidase encoding genes. Culture dependent approach was used to screen 39 and#945;- galactosidase positive isolates and on the basis of high enzyme yield/temperature optima, one isolate was selected and identified as Bacillus flexus JS27. Maximum production of the enzyme from Bacillus flexus JS27 was achieved in guar gum (1.5% w/v) and soybean meal (1% w/v) after 72 h by using 2% v/v inoculum of 18 h at 150 rpm. Temperature/pH of production was optimized at 50 and#870; C and 7.0 respectively. Two isoenzymes (and#945;-gal I and II) were screened/ characterized on the basis of temperature/ pH optima and their stability. and#945;-Gal II was selected and further purified by using Sephacryl S-100 column chromatography. Final purification with specific activity (4234.3 U/mg), purification fold (11.54) and yield (48.27 %) was achieved. Native-PAGE and SDS-PAGE showed molecular weight of the enzyme as 86 and 41 kDa respectively. and#945;-Gal II used sugar/sugar alcohols, oligosaccharides and complex carbohydrates as substrates.