Catalyzes the hydrolysis of alpha,alpha-trehalose into two molecules of D-glucose. alpha,alpha-trehalose + H2O = alpha-D-glucose + beta-D-glucose kcat is 1.60 sec(-1) at 50 degrees Celsius and pH 3.7. kcat is 3.43 sec(-1) at 70 degrees Celsius and pH 3.7. Optimum pH is 3.7. More than half of the maximal activity is observed over a range between pH 3.5 and 4.5. Optimum temperature is 70 degrees Celsius. Glycan degradation; trehalose degradation; D-glucose from alpha,alpha-trehalose: step 1/1. Belongs to the glycosyl hydrolase 15 family.