#FEMSmicroBlog: Making the world greener (with yeast)

11-05-2021

In the search for green energy sources, researchers often look at microbial cell factories generating bioproducts. Yeast is a promising cell factory platform able to assimilate and degrade sugars from lignocellulosic biomass present in renewable plant waste. The new study “Identification of novel pentose transporters in Kluyveromyces marxianus using a new screening platform” published in FEMS Yeast Research sheds light on how yeast imports pentose sugars from plant waste for their degradation. Lorena Donzella presents for the #FEMSmicroBlog how the identification of sugar transporters in yeast can help develop sustainable biorefinery platforms. #FascinatingMicrobes

 

Plant waste to overcome environmental challenges

We are currently facing environmental challenges like energy demand, the limited availability of fossil fuel reserves, and a growing world population. These led to the development of the concept of bioeconomy and the search for new renewable energy sources.

Lignocellulosic biomass (LCB) is a promising feedstock that has greatly attracted attention for being an abundant and renewable waste from plants. It allows circular economy growth and bioproducts production due to its sustainability and its carbon-neutral nature. Nowadays, microbial cell factories have been used to convert LCB waste into useful, high-added value products like biochemicals and biofuel. Until now, these were produced by means of fossil resources.

About 60% of the sugars derived from LCB are hexoses like glucose, and microbes can easily degrade those. The remaining 40% are pentose sugars, namely xylose and arabinose, which are more problematic. However, for the development of next-generation biorefineries in the context of a bioeconomy development, it is important that microbes degrade all available sugars.

For an efficient and sustainable biorefinery, it is important that the involved microbe can assimilate and degrade all available sugars in the waste sample.

 

A yeast platform for a greener environment

The uptake of pentose into the microbial cell is one of the main bottlenecks that complicates sugar utilization. Microbial metabolism prevents the simultaneous consumption of hexoses and pentoses, which has a negative impact on the productivity and yields of the entire degradation process. Thus, the capacity to assimilate pentoses strongly depends on the presence and activity of membrane transporters to import these sugars.

The yeast Kluyveromyces marxianus is a very promising yeast cell factory that is able to produce lots of interesting products, from bioenergy (bioethanol) to biochemicals (aromatic compounds, drugs and nutraceuticals) and lytic enzymes (inulinase, β-galactosidases and pectinases). While the yeast is naturally able to assimilate the pentoses in lignocellulosic biomass, K. marxianus has also advantageous traits as rapid growth and thermotolerance.

 

Novel sugar transporters from a yeast cell factory

The paper “Identification of novel pentose transporters in Kluyveromyces marxianus using a new screening platform” published in FEMS Yeast Research expands the knowledge on sugar transporters in this promising yeast cell factory. Using new genome engineering and synthetic biology tools, the study introduces a novel screening platform to investigate pentose transporters in a native pentose-utilising yeast.

 Phylogenetic comparison of potential sugar transporters from different yeast strains
Phylogenetic comparison of potential sugar transporters between different yeast strains. From Donzella et al. (2021).

With the introduced screening platform, the study shows that yeast uses several pentose transporters to overcome the limiting capacity to grow on inexpensive carbon sources. One can imagine that these new pentose transporters could serve as the foundation to engineer protein transporters with new kinetic functionalities.

This study expands the knowledge of the evolution of sugar transporters in yeasts and increases the set of native pentose transporters in an industrially relevant species. Hopefully, this set the first stone to build an industrial platform to be applied in biorefineries.

 

About the author of this blog

Lorena Donzella holds a Bachelor and a Master in Environmental and Industrial Biotechnology from the University Aldo Moro di Bari (Italy). She is currently involved in the ITN YEASTDOC doing her PhD in Microbial Biotechnology at the Universidade do Minho in Portugal and at the University College Cork in Ireland. She is passionate about environmental problems and the huge potential of yeasts that can help to solve them. She believes industrial biotechnology is the key to obtain new interesting yeast strains with sustainable and green applications.

About this blog section

The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.

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