Characterization and Development of Salt-Resistant Aspergillus oryzae for Marine-Derived Enzyme Expression

Marine-derived enzymes often show distinct physiological properties and great potential for industrial use. Salt ions may improve the stability and expression efficiency of marine enzymes, which requires salt-resistant host based expression platform. Aspergillus oryzae of good protein expression and secretion was evaluated and explored for this purpose. Growth, sporulation, secreted extracellular proteins and transcriptome-based metabolic characteristics under artificial seawater condition were analyzed. Also, genetic manipulation system was developed and compared in various strains. Finally, A. oryzae AS 3.487 was recognized as a dominant chassis host. Efficient constitutive and artificial seawater-inducible promoters were screened from the transcriptomic data, which were further evaluated using marine alginate lyase AlgI as the reporter. Medium and condition optimizations improved enzyme production subsequently. Multicopy expression strategy further achieved a maximum enzyme production of 797 U/mL in flask culture. This study provides new references for the heterologous expression of marine-derived enzymes under high-salinity culture conditions.