Multiple amino acid substitutions significantly improve the thermostability of feruloyl esterase A from Aspergillus niger.

Feruloyl esterase A from Aspergillus niger (AnFaeA) is one of the most important feruloyl esterases of industrial relevance. Previous work aided by the PoPMuSiC algorithm has identified two beneficial mutants (D93G and S187F) with thermostabilization effect. In this work, twelve additional amino acid substitutions were identified to be beneficial to the thermostability of AnFaeA after screening a random mutagenesis library constructed in Pichia pastoris. Combination of these mutations resulted in a mutant with 80% residual activity after heat treatment at 90 °C for 15 min and a half-life increasing from 15 min to >4000 min at 55 °C. The thermostabilized mutant displayed significantly enhanced performance compared to the parental AnFaeA when applied to the treatment of steam-exploded corn stalk at 60 °C together with an xylanase, demonstrating its great potential for industrial application.