High-level expression of Aspergillus niger lipase in Pichia pastoris: Characterization and gastric digestion in vitro

The low expression level of acidic lipases from Aspergillus sp. remains a major obstacle for their use in industrial applications. In this study, fusion expression with three fusion partners was investigated to enhance the expression level of an acidic lipase from A. niger (ANL) in Pichia pastoris. When fused with a small ubiquitin-related modifier (SUMO), designated SANL, the highest activity reached 960 ± 40 U/mL in a 3 L fermenter, which was 1.85-fold higher than that of the parent ANL. SANL exhibited its maximum activity at pH 2.5 and had lower Km and higher kcat/Km values than those of ANL. In gastrointestinal digestion experiments, SANL was resistant to pepsin and had high hydrolytic activity against triolein from pH 3.0 to 6.0. However, SANL was significantly inhibited by NaTDC above its CMC, which may limit its application for intestinal digestion, but allow it to remain suitable for gastric digestion.