Maltose is a disaccharide formed from two units of glucose joined with an α(1→4) bond, a reducing sugar. Maltose monohydrate can be used as an energy source for bacteria. It is the two-unit member of the amylose homologous series, which is the key structural motif of starch. When beta-amylase breaks down starch, it removes two glucose units at a time, producing maltose. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond.