The invention relates to uses of polypeptides having amylase activity, nucleic acids encoding them, and methods for making and using them. For example, in one aspect, the invention provides methods for making alcohol using polypeptides of the invention. In one aspect, the polypeptides having amylase activity have increased activity and stability at acidic, neutral and alkaline pH and increased temperature. In one aspect, the invention provides methods for producing an alcohol, for producing a high-maltose or a high-glucose syrup or a mixed syrup, for liquifying a starch-comprising composition, for hydrolyzing a starch, comprising use of polypeptides of the invention, or polypeptides encoded by the nucleic acids of this invention.