Macroscopic modelling of the growth and substrate consumption of wild type and genetically modified Pichia pastoris.

Pichia pastoris is a popular yeast platform to generate several industrially relevant products which have applications in a wide range of sectors. The complexities in the processes due to the addition of a foreign gene are not widely explored. Since these complexities can be dependent on the strain characteristics, promoter, and type of protein produced, it is vital to investigate the growth and substrate consumption patterns of the host to facilitate customised process optimisation. In this study, the growth rates of P. pastoris GS115 wild type and genetically modified strains grown on glycerol and methanol in batch cultivation mode were estimated and the model providing the best representation of the true growth kinetics based on substrate consumption was identified. It was observed that the growth of P. pastoris exhibits Haldane kinetics on glycerol rather than the most commonly used Monod kinetics due to the inability of the latter to describe growth inhibition at high concentrations of glycerol. Whereas, the Cardinal Parameter Model, a newly proposed model for this application, was found to be the best fitting to describe the growth of P. pastoris on methanol due to its ability to describe methanol toxicity. Interestingly, the findings from this study concluded that in both substrates, the genetically engineered strain exhibited a higher growth rate compared to the wild type strain. Such an observation has not been established yet in other published works, indicating an opportunity to further optimise the carbon source feeding strategies when the host is grown in fed-batch mode. This article is protected by copyright. All rights reserved.