The acetyl xylan esterases (EC 3.1.1.72) (AXEs) could hydrolyse the ester linkages of the acetyl groups in position 2 and/or 3 of the xylose moieties of natural acetylated xylan present in the plant cell wall and play an important role in the plant cell wall hemicellulose biodegradation.A new Volvariella volvacea gene encoding an acetyl xylan esterase (designated as Vvaxel) was cloned.In an attempt to obtain high level expression of VvAXE1,we replaced all codons by the most-or second-preferred frequently used in Pichia pastoris genes without modifying the protein sequence.The GC content of the eodon-modified Vvaxel was reduced from 55.49 % to 48.62 %.