Catalyzes the reversible phosphorolytic cleavage of trehalose. Phosphorolysis is specific for trehalose. alpha,alpha-trehalose + phosphate = beta-D-glucose 1-phosphate + D-glucose Optimum pH is 7.0-8.0. Optimum temperature is 75 degrees Celsius. Glycan degradation; trehalose degradation. Homodimer. Belongs to the glycosyl hydrolase 65 family.