Hydrolysis of (1->4)-beta-D-galactosidic linkages in agarose, giving the tetramer as the predominant product. Optimum pH is 8.0. Active from pH 6.0 to 10.0. Optimum temperature is 40 degrees Celsius. Active at temperatures up to 50 degrees Celsius. Belongs to the glycosyl hydrolase 16 family.