Ta0-a, the gene encoding the mature antimicrobial peptide tachyplesin II, was engineered to optimize the coding sequence according to codon usage bias in yeast. Ta0-a was efficiently expressed in the methylotrophic yeast Pichia pasTOris strain SMD1168. The recombinant peptide to reached 150 mg/L after methanol induction for 6 d. Ta0 was rapidly purified to homogeneity by a single step of size-exclusion chromatography. The minimal lethal concentrations of Ta0 to the Escherichia coli strain K12 was 30 mu g/mL. Ta0 exhibited a wide range of antimicrobial activity: the growth of 26 bacterial and fungal strains, including some typical food/feed spoilage microorganisms, was all substantially inhibited. This result indicates the potential practical application of the recombinant peptide in various industrial products. (C) 2007 Elsevier Inc. All rights reserved.