Abstract: In order to construct a plasmid with the hygromycin phospotransferase gene as a selectable marker to express antimicrobial peptide LL37 in Picha pastori,Zeocin resistance gene in pGAPZαA was replaced by the hygromycin phospotransferase gene through EcoRⅤ, BamHⅠ restriction enzyme digestion,the new plasmid was named as pGAPHαA. LL37 gene was designed and synthesized to include the partiality codons of P.pastoris,then it was cloned into the pGAPHαA vector and transformed into P.pastoris SMD1168 by electroporation. The transformants were screened with hygromycin B. Up to 167 mg/L LL37 was produced in culture medium. Expression product of heat resistance. Agrose diffusion assay showed that LL37 had potent antibacterial activity against both Gram-negative and Gram-postive bacteria,with MIC of 2.94 μg/mL, 7.06 μg/mL against E.coli DH5α and Streptococcus suis,respectively.

Key words: hygromycin phospotransferase gene; pGAPHαA; antimicrobial peptide LL37; P.pastoris