FIG. 7.

β-Glycosidase activity test of isolated clones transformed with pEXlacOP. (A) Four independent transformants were picked from lactose plates, propagated in hygromycin selective medium, and seeded onto fresh plates (1, 2, 3, and 4). After growth, the colonized areas showed β-glycosidase activity, developing blue color upon being stained with the chromogenic substrate X-Gal. Wild-type Gθ and the deficient mutant GθW were used as positive and negative controls for enzyme detection, respectively. Cultures of the same clones were grown to early stationary phase and reinoculated for a subsequent four-step scaling up. Cells were harvested at the early stationary phase of growth for each step, and extracts were assayed for cytosolic β-galactosidase activity (in enzyme units per milligram of total cytosolic proteins). (B) Results for cultures (1, 2, 3, and 4) in both yeast extract-Casamino Acids-glucose (open bars) and tryptone-lactose (solid bars) media at the first (Y1 and T1) and the fourth (Y2 and T2) step of propagation. Activities in the cell extracts of Gθ and GθW (w) cultures were used as reference points for 100 and 0% activity, respectively, in every set of measures.