An inducible Komagataella phaffii system for protein expression using sorbitol dehydrogenase promoter

The aim of the present work was to develop a methanol-independent Komagataella phaffii (K. phaffii) strain using a non-methanol promoter.

In this study, the food grade enzyme xylanase from Aspergillus niger ATCC 1015 was used as the reporter protein, a recombinant K. phaffii containing a cascade gene circus was designed and constructed using sorbitol as inducer. Sorbitol induced P_SDH leading to MIT1 expression firstly, and heterologous protein xylanase expression finally. This system showed 1.7 fold of xylanase activity at the condition of single copy number of extra MIT1, and 2.1 fold of xylanase activity at condition of multi-copy extra MIT1 gene.

This sorbitol-induced expression system of K. phaffii avoided toxic and explosive methanol. It was a novel cascade gene expression and a food safety system.