Enhanced Heterologous Protein Production In Aspergillus niger Fermentation Through Protease Inhibition Using Bioprocess Enigneering Strategies

摘要

Filamentous fungal organisms such as A. niger are attractive hosts for the production of heterologous proteins due to their advantageous growth characteristics, their ability to perform correct posttranlational modification such as glycosylation, and to secrete high levels of protein production into the medium (van den Hombergh et al., 1997). However, heterologous protein secretion is often severely hampered by fungal proteases. Several biological strategies have been developed to increase these yields. Those employed include the introduction of a large number of gene copies (Withers et al., 1998), the use of strong promoters and efficient fungal secretion signals (Archer et al., 1997) and the developmetn of protease-deficient host strains (van den Hombergh et al., 1997). One of the most successful strategies involves the construction of gene fusion of the target gene to a highly expressed fungal gene, such as glucoamylase (Ward et al., 1990). The resulting fusion protein progresses through the fungal secretory pathway like the normal, homologous protein, before separation in the external medium. However, even with successful secretion of higher levels of heterologous proteins, the problem of proteolytic degradation by extracellular proteases still remains.