Figures & data
Figure 1. Multiple alignments of representative β-galactosidases from thermophiles.
Note: GenBank accession numbers: YP003842858.1 (Clostridium cellulovorans 743B), YP003993284.1 (Caldicellulosiruptor hydrothermalis 108), YP004027282.1 (Caldicellulosiruptor kristjanssonii 177R1B), YP003839732.1 (Caldicellulosiruptor obsidiansis OB47) and YP002251501.1 (Dictyoglomus thermophilum H-6-12).
Figure 2. Purification of the recombinant β-galactosidase.
Note: protein marker (M); total proteins from control bacterium (containing only vector), non-induced (lane 1); total proteins from control bacterium (containing only vector), induced (lane 2); total proteins from recombinant bacterium (containing β-galactosidase gene), non-induced (lane 3); total proteins from recombinant bacterium (containing β-galactosidase gene), induced (lane 4); purified GST-β-galactosidase fusion protein (lane 5).
Figure 3. Effects of temperature on recombinant β-galactosidase activity (A) and stability (B).
Note: The recombinant β-galactosidase activity was evaluated in a 0.05 mol/L sodium phosphate buffer (pH 7.0) at various temperatures (35, 45, 55 , 65, 75, 85 and 95 °C) (A); to assess the stability of the enzyme, the enzyme solution was preincubated in 0.05 mol/L sodium phosphate buffer (pH 7.0) at 75, 80, 85, 90 and 95 °C for 30 min (B). The assayed activity under the conditions 75 °C and pH 7.0 was defined as 100% relative activity.
Figure 4. Effects of pH on β-galactosidase activity (A) and stability (B).
Note: The optimum pH was assayed at 75 °C using buffer solutions with various pH values ranging from 4.0 to 10.0 (A); in order to assess stability, the enzyme was incubated in different pH buffers (pH 4.0–10.0) at 75 °C for 30 min (B). The assayed activity under the conditions 75 °C and pH 7.0 was defined as 100% relative activity.
Figure 5. Effects of metal ions (A) and additives, and detergents (B) on β-galactosidase activity.
Note: The recombinant β-galactosidase activity was evaluated in 0.05 mmol/L sodium phosphate buffer (pH 7.0) at 75 °C in the presence of the described metal ions (A), additives and detergents (B). The assayed activity under the conditions 75 °C and pH 7.0 without the added metal ions, additives and detergents was defined as 100% relative activity.
