Bioprocesses need to be optimized to meet economical and production requirements. Large-scale processes present numerous perturbations that make the fermentation unpredictable and suboptimal. Therefore, it is paramount to develop strains exhibiting consistent functionality, even when exposed to varying conditions e.g. robust strains. Illustration: Luca Torello Pianale
Fermentation processes are commonly used for the production of a broad range of products that we know from daily life, for instance baker’s yeast, yoghurt, lactic acid, ethanol, enzymes, and pharmaceutical proteins. While transitioning to a fossil-free society, bioprocesses using biomass and waste materials as a starting material receive increasing attention. Microorganisms can be used in such processes – they have adapted and evolved in nature to achieve the best potential for survival in certain ecological niches.
“However, when we take a microorganism and bring it into a bioprocess, it works under completely different conditions and its tolerance and performance might be far from optimal due to the different and harsh conditions it has to work under. In this view, microbial robustness is an essential feature which industries strive for”, says Lisbeth Olsson, Professor in Industrial Biotechnology at Chalmers.
Robustness can be described as the stable performance of a system despite perturbations in the environment.
“I have long been fascinated by investigating microbial robustness to understand its fundamental and apply the knowledge towards bioprocesses”, says Lisbeth Olsson.
Measuring microbial robustness will improve processes
In a newly published study, her research group explains the value of microbial robustness for industrial fermentation processes. When establishing or developing industrial processes, you select the microorganism to do the right job. For instance, if you want to produce beer, you choose a beer yeast, and not a wine yeast. The same consideration needs to be done with respect to microbial robustness when choosing a strain for a new bioprocess. However, it is difficult to evaluate differences in robustness between different microbes.
“We foresee that being able to measure and quantify the robustness of microorganisms will be a cornerstone in efficiently choosing strains for bioprocesses”, says Cecilia Trivellin, PhD student at the Division of Industrial Biotechnology at Chalmers.
The researchers study how the concept of measuring the robustness of microorganism properties (e.g., if a yeast has a stable production of ethanol) can be used for industrial purposes.
“Different microorganism candidates can be challenged with a set of key industrial conditions in a high-throughput setup and the robustness of different properties measured. Thereby, it is possible to predict which of the microorganisms will be more stable when exposed to large scale industrial environments.”, says Cecilia Trivellin.
New toolbox to investigate importance of subpopulations
One of the players in establishing the performance stability of a strain might be the ability of a specific strain to form subpopulations. In the last years, an increasing number of papers highlighting this phenomenon has been published. Although all the cells in a bioprocess should be the same, subpopulations with different physiological behaviours can be seen and the explanation for these differences might hide inside the cell. So far, investigation of the intracellular environment in cell factories during bioprocesses has been poorly explored. In order to achieve that, it is possible to use fluorescent biosensors, i.e., tools able to detect variations in compounds or conditions inside the cell.
“In my latest publication, I focused on the development of a toolbox of biosensors able to sense different key intracellular parameters to explore their connection with robustness. This sets the basis for the investigation and a deeper understanding of large-scale bioprocesses and the role of subpopulations,” says Luca Torello Pianale. PhD student at the Division of Industrial Biotechnology at Chalmers.
In the researchers continued work, they will focus more on single-cell aspects as part of how a cell population develop.
“Some situations where we will apply the tools that we have built will include strain analysis during development using laboratory adaptive evolution and for probiotic yeast,” says Lisbeth Olsson.
Read the full review by the authors Lisbeth Olsson, Peter Rugbjerg, Luca Torello Pianale and Cecilia Trivellin: Robustness: linking strain design to viable bioprocesses
Lisbeth Olsson, Peter Rugbjerg, Luca Torello Pianale and Cecilia Trivellin at the Division of Industrial Biotechnology.
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