Pichia pastoris is a constitutive as well as inducible model for recombinant protein. P. pastoris glyceraldehyde 3-phosphate dehydrogenase (GAP) gene promoter provides strong constitutive expression on glucose at a level. While AOX1 gene results in repression and depression mechanism which is dependent on methnol for induction.

The use of methanol to induce gene expression may not be appropriate for the production of food products since methane, a petroleum-related compound, is one source of methanol. Also, methanol is a potential fire hazard, especially in quantities needed for large-scale fermentations