Abstract
Komagataella phaffii, also known as Pichia pastoris, is a powerful host for recombinant protein production, in part due to its exceptionally strong and tightly controlled P(AOX1) promoter. Most K. phaffii bioprocesses for recombinant protein production rely on P(AOX1) to achieve dynamic control in two-phase processes. Cells are first grown under conditions that repress P(AOX1) (growth phase), followed by methanol-induced recombinant protein expression (production phase). In this study, we propose a methanol-free approach for dynamic metabolic control in K. phaffii using optogenetics, which can help enhance input tunability and flexibility in process optimization and control. The light-responsive transcription factor EL222 from Erythrobacter litoralis is used to regulate protein production from the P(C120) promoter in K. phaffii with blue light. We used two system designs to explore the advantages and disadvantages of coupling or decoupling EL222 integration with that of the gene of interest. We investigate the relationship between EL222 gene copy number and light dosage to improve production efficiency for intracellular and secreted proteins. Experiments in lab-scale bioreactors demonstrate the feasibility of the outlined optogenetic systems as potential alternatives to conventional methanol-inducible bioprocesses using K. phaffii.