GH61 Polypeptide Variants and Polynucleotides Encoding Same

A variant GH61 polypeptide having cellulolytic enhancing activity, comprising a substitution at one or more positions corresponding to positions 105, 154, 188, 189, 216, and 229 of the mature polypeptide of SEQ ID NO:

• 30, wherein the substitution at corresponding position 105 is with Pro or Lys, the substitution at corresponding position 154 is with Ile or Leu, the substitution at corresponding position 188 is with Ala, Phe, Met, or Trp, the substitution at corresponding position 189 is with His or Lys, the substitution at corresponding position 216 is with Leu or Tyr, and the substitution at corresponding position 229 is with Trp, His, Ile, or Tyr, wherein the variant has cellulolytic enhancing activity, wherein the variant has increased thermostability relative to a GH61 polypeptide without the substitution at the one or more positions corresponding to positions 105, 154, 188, 189, 216, and 229 of the mature polypeptide of SEQ ID NO:
• 30, and wherein the variant has at least 95% sequence identity, but less than 100% sequence identity, to the mature polypeptide of SEQ ID NO:
• 2, 4, 6, 8, 10, 12, 16, 18, 20, 22, 24, 26, 28, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 166, 168, 170, 172, 174, 176, 178, 180, 182, 184, 186, 188, 190, 192, 194, 196, 198, 200, 202, 204, 206, 208, 210, 212, 214, or 216.