What you need to know about Pichia pastoris

The methylotrophic yeast called Pichia pastoris has now become a crucial host for recombinant protein production. This organism can utilize methanol as its carbon source. You should note that the methanol utilization pathway tends to describe the catalytic reactions which occur during methanol metabolism. 

Remember that industrial production of recombinant therapeutic proteins, such as monoclonal antibodies happens to be one of the areas that has experienced significant improvements with the introduction of a wide range of novel technologies. To reduce the manufacturing timeline and cost, some technologies have been developed for other categories of drugs. These include an engineered production host, media and feed selection, and many more. This page discusses what you need to know about Pichia pastoris.

Use of Pichia pastoris

The yeast Pichia pastoris belongs to the genus called komagataella. This yeast was first used in biotechnology around the 1960s to produce single-cell protein for feed applications and food because it can metabolize methanol. 

The huge presence of fossil gas was the main driver that encouraged research on the use of methylotrophic microorganisms. Some experts then used Pichia pastoris to be the host for recombinant protein production based on its strong methanol-regulated promoters. 

Since then, this yeast has become a popular way of producing technical enzymes and pharmaceutical proteins. Methanol-based production can be quite effective, but it has some technical limitations because of the features of methanol assimilation. Methanol oxidation can use large quantities of oxygen and leads to the evolution of significant biochemical reaction heat. Both of these can reach the limits of large-scale bioreactors.

The development of new promoters has offered solutions to less intense bioprocesses that are based on glycerol or glucose as the carbon source. Some of these include a methanol-independent variant of the AOX1 promoters and the GTH1 which is a glucose transporter.

Producing the carbon catabolite repression systems or even transcriptional regulators that are responsible for methanol-dependent induction provides a good genetic chance that can allow you to do methanol-free expression using AXO1 promoter in Pichia pastoris.  

Also, engineering protein folding and secretion offered extra solutions to improve the production of recombinant proteins. Today, Pichia pastoris has also been used to produce metabolites. Keep in mind that metabolic engineering was utilized to make and improve native and heterologous pathways. Most metabolites that have been produced in Pichia pastoris are complex secondary molecules like terpenoids and carotenoids. It’s safe to assume that the regulated and limited carbon metabolism alongside the pentose phosphate pathway flux can help this yeast when it comes to the production of the complex reduced molecules unlike Saccharomyces cerevisiae that has high metabolic rates that cause fermented byproducts of primary metabolism. 

Using Pichia pastoris as a chassis cell

Synthetic biology tries to bring standardization and design principles of other engineering concepts into biotechnology. And, one of the elements of these design principles is called the chassis. This acts as a carrier for several modules that are specific for various production purposes.

You should remember that the chassis is considered to be an independently replicating cell that is designed to provide the required precursors, such as energy for a certain pathway. Some experts consider a chassis cell as a self-replicating minimal machine that aims at constituting a platform requiring further engineering so that it can produce specific biomolecules. In such cases, a chassis cell can be a platform you can use to produce either small molecule metabolites or proteins, or even both.

Many scientists believe that synthetic biology can depend on a few number of chassis organisms, which include bacteria like Escherichia coli and Bacillus subtilis as well as yeasts, such as S. cerevisiae. This yeast has the best chance of being used as a chassis because it has been used for a long time for bio-based production. Also, it has been utilized as an organism model in genetics for decades. It’s worth remembering that there are also many other yeast platform organisms that you can use for bioproduction.  

There are some features that make an organism a good chassis. These include its substrate use, nutrient demand, and metabolic by-products. A good chassis should also be stress tolerant and genetically stable, provide metabolic precursors, redox, and energy, and ease of accessibility and manipulation of genetic methods and parts. S. cerevisiae tends to fulfill most of these traits when it comes to producing direct metabolic byproducts like ethanol. But there are also some downsides, especially involving the metabolic network because it has now become unbalanced. As a result, there is usually too much by-product formation and metabolism

On the other hand, Pichia pastoris has a simple genetic makeup compared to S. cerevisiae because it didn’t go through genome duplication. It doesn’t show this overflow metabolism because it has a well-regulated carbon metabolism. Even better, Pichia pastoris has a low maintenance energy demand that leads to a slow growth. This happens to be a main feature of a good chassis. Also, one-carbon metabolism is regarded as the major feature in bio-refinery concepts. 

You should note that methanol can be derived from carbon dioxide by reducing renewable energy. And, it can be used for bio-production utilizing methylotrophic microorganisms. Alternatively, the assimilation of the methanol into the Pichia pastoris pathway was used as a chassis to produce an autotrophic, carbon dioxide assimilating yeast. Carbon dioxide can also be thought of as a co-substrate to make organic acids.  

As explained earlier, Pichia pastoris has been used for many years as a model organism for studies. The introduction of the methanol use pathway can now lead to a huge proliferation of peroxisomes. This makes it a great tool to help you to study formation. You can use it to study the accumulation and degradation of organelles that can be crucial for beta-oxidation of fatty acids in eukaryotic cells. 

The secretory pathway like the Golgi structure of Pichia pastoris resembles that of higher eukaryotic cells than S.cerevisiae. Therefore, you can use Pichia pastoris as a model organism to help you study human diseases and eukaryotic cell biology. The Golgi arrangement can also be a good reason why this yeast secretes recombinant proteins efficiently compared to S.cerevisiae.

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