Phenotypeca’s process of breeding and QTL analysis enables the selection of strains with enhanced secretory pathways (e.g., from the endoplasmic reticulum to the Golgi body), chaperone co-expression and ideal redox environments to improve folding capabilities in conjunction with targeted engineering. Engineering includes modifying chaperone expression and the unfolded protein response. A key aspect of the production in yeast of proteins with disulfide bonds is to optimise expression levels, since overexpression can induce improper folding. Two methods in this optimisation are the modification of gene copy number and the adjustment of promotor strength. Beyond this approach, the optimisation of culture conditions (including temperature, pH, aerobic conditions, etc.) and the development of protease deficiency are further techniques to reduce the frequency of improper folding. Characterisation by analytical techniques enables these techniques to be informed and quality control procedures to be implemented.