Culture broth methanol concentration is the key parameter in the production of recombinant proteins by using Pichia pastoris (Komagataella phaffii) as a cell factory under the regulation of the methanol-inducible Alcohol Oxidase 1 (AOX1) promoter (PAOX1) or other alternative promoters induced directly or indirectly by methanol. Accordingly, the implementation of an efficient methanol monitoring and control system is critical to guarantee the proper methanol concentration toward achieving an efficient and robust production while assuring reproducible bioprocessing conditions.