Kinetic studies on exploring lactose hydrolysis potential of ? galactosidase extracted from Lactobacillus plantarum HF571129.

ABSTRACT: A novel intracellular ?-galactosidases produced by Lactobacillus plantarum HF571129, isolated from an Indian traditional fermented milk product curd was purified and characterized. The ?-galactosidases is a hetrodimer with a molecular weight of 60 kDa (larger subunit) and 42 kDa (smaller subunit), as estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme was purified 7.23 fold by ultrasonication, ultrafiltration and gel filtration chromatography with an overall recovery of 30.41 %. The optimum temperature for hydrolysis of its preferred substrates, o-nitrophenyl- ?-D-galactopyranoside (ONPG) and lactose, are 50 °C (both), and optimum pH for these reactions is 6.5 and 7.5, respectively. The ?-galactosidases showed higher affinity for ONPG (Km, 6.644 mM) as compared to lactose (Km, 23.28 mM). Galactose, the end product of lactose hydrolysis was found to be inhibited (47 %). The enzyme activity was drastically altered by the metal ion chelators EDTA, representing that this enzyme is a metalloenzyme. The enzyme was activated to a larger extent by Mg(2+) (73 % at 1 mM), while inhibited at higher concentrations of Na(+) (54 % at 100 mM), K(+) (16 % at 100 mM) and urea (16 % at 100 mM). The thermal stability study indicated an inactivation energy of Ed?=?171.37 kJ mol(-1). Thermodynamic parameters such as ?H, ?S and ?G, were determined as a function of temperature. About 88 % of lactose was hydrolyzed at room temperature within 1 h. The study suggested that this enzyme showed its obvious superiority in the industrial lactose conversion process.

SUBMITTER: Selvarajan E 

PROVIDER: S-EPMC4573140 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature