Production and optimization of a kiwi pectin methylesterase inhibitor in Pichia pastoris GS115

Gene sequence coding of a kiwi pectin methylesterase inhibitor was optimized, synthesized, and expressed in Pichia pastoris GS115 based on P. pastoris preferred codon usage. The expression level of the recombinant protein (kwPMEI) increased by 89.74% after codon optimization. Expression conditions of recombinant strains were optimized. The highest production of kwPMEI was achieved using 0.8% sorbitol (added every 24 h), 0.05% oleic acid (added at the beginning of induction), and 0.5% methanol (added every 12 h). kwPMEI was purified using Ni²⁺ chelating affinity chromatography and 17 mg of the protein was harvested from 60 mL of a culture supernatant. Activity analysis showed that kwPMEI efficiently inhibited the activity of different plant PMEs. High expression levels and purification of kwPMEI will promote applications in fruit and vegetable juices.