Competent P. pastoris GS115 cells were prepared according to the method described by Invitrogen. The plasmid of pPIC9K-Hewl or pPIC9K-XynCDBFV-Hewl was linearized by BglII (TAKARA, Japan), followed by transformation into P. pastoris GS115 by electroporation [19 (link)]. Positive transformants were screened using MD plates without histidine, and high copy transformants were then screened by YPD plates containing 3.5 g/L geneticin G418 [20 ].