Thermus thermophilus as source of thermozymes for biotechnological applications: Homologous expression and biochemical characterization of an alpha-galactosidase

Background: The genus Thermus, which has been considered for a long time as a fruitful source of biotechnological relevant enzymes, has emerged more recently as suitable host to overproduce thermozymes. Among these, ?-galactosidases are widely used in several industrial bioprocesses that require high working temperatures and for which thermostable variants offer considerable advantages over their thermolabile counterparts. Results: Thermus thermophilus HB27 strain was used for the homologous expression of the TTP0072 gene encoding for an ?-galactosidase (TtGalA). Interestingly, a soluble and active histidine-tagged enzyme was produced in larger amounts (5â mg/L) in this thermophilic host than in Escherichia coli (0.5â mg/L). The purified recombinant enzyme showed an optimal activity at 90â °C and retained more than 40% of activity over a broad range of pH (from 5 to 8). Conclusions:TtGalA is among the most thermoactive and thermostable ?-galactosidases discovered so far, thus pointing to T. thermophilus as cell factory for the recombinant production of biocatalysts active at temperature values over 90â °C.