Involved in the degradation of methyl tert-butyl ether (MTBE). Catalyzes the conversion of hydroxyisobutyraldehyde to hydroxyisobutyric acid (HIBA). 2-hydroxy-2-methylpropanal + H2O + NAD(+) = 2-hydroxy-2-methylpropanoate + 2 H(+) + NADH Induced in the presence of MTBE or tert-butyl alcohol (TBA). Belongs to the aldehyde dehydrogenase family.