Polypeptides with alkaline alpha-amylase activity and nucleic acids encoding them

Isolated polypeptide with alpha-amylase activity comprising the amino acid sequence of SEQ ID No. 2 and variants thereof having an amino acid sequence with at least 96% identity with amino acids 1 to 485 of SEQ ID NO. 2, where the variant has an improved washing performance compared to the progenitor alpha-amylase, where the washing performance is determined under the following washing conditions: test samples soiled with orange rice starch are washed for 15 minutes at 25 ° C at a pH of 10.5, a water hardness of 6 ° dH and a Ca: Mg ratio of 2: 1 in a solution of 3g / l of A / P model detergent consisting of: 20% tripolyphosphate sodium, 25% Na2SO4, 15% Na2CO3, 20% linear alkylbenzene sulphonate, 5% C12-C15 ethoxylated alcohol, 5% Na2Si2O5 and 0.3% NaCl, containing 1 mg / l of the polypeptide with alpha-amylase activity; After washing the samples are evaluated by measuring the remission at 460 nm and the washing performance is determined as the remission of the washed samples minus the remission of a washed sample under the same conditions but without a polypeptide with alpha-amylase activity.