Searching for Novel Thermostable β-galactosidases

Abstract

β-galactosidases are biotechnologically interesting enzymes for the hydrolysis of lactose and GOS synthesis. The main objective of this work was to analyze the microbial community structure and the functional potential of As Burgas hot spring, focusing on the discovery of novel thermostable β-galactosidases in this thermal ecosystem. A novel thermostable β-galactosidase, named BWbg1, was discovered through functional screening of a metagenomic library from As Burgas water. The high thermal stability displayed by the enzyme, with an optimum temperature of 80 °C and optimum pH close to the pH of milk, coupled with its high GOS yield production, make BWbg1 a very suitable catalyst for the dairy industry. Proteobacteria are the main inhabitants of As Burgas hot spring. The functional analysis reveals the importance and correlation between carbon, nitrogen, sulfur, and hydrogen cycles in As Burgas. From the two β-galactosidases found by sequence annotation, only pTsbg showed hydrolytic activity towards ONPG, but was unable to hydrolyze lactose. The significant differences between As Burgas population and the nearby Muiño da Veiga hot spring are mostly associated with their variability in the geochemical water composition. Temperature and pH are two important factors shaping hot springs’ microbial community, as was determined by comparative analysis with other thermal springs.