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Less is more: genome-reduced Bacillus subtilis for protein production

PhD ceremony:R. (Rocío) Aguilar Suarez, PhD
When:December 09, 2020
Start:14:30
Supervisor:prof. dr. J.M. (Jan Maarten) van Dijl
Co-supervisor:dr. ing. G. (Girbe) Buist
Where:Academy building RUG
Faculty:Medical Sciences / UMCG

Bacteria  are nowadays widely used as cell factories for production of enzymes and pharmaceutical products that, respectively, replace wasteful chemical processes and support human health and wellbeing. However, not all societal demands can be adequately met with current bacterial production strains. Genome engineering could offer the possibility to create novel strains with the desired properties. The present PhD thesis describes research on genome-minimised strains of the popular bacterial cell factory Bacillus subtilis, a non-pathogenic soil bacterium that is often used to produce enzymes and vitamins at industrial scale. The results show that strains lacking 26%, 31% or even 35% of the genome gained the ability to efficiently secrete antigens of the major human pathogen Staphylococcus aureus. This is an important observation, as it opens up the possibility to apply engineered strains for large-scale vaccine production, which is not possible with current production strains. To pinpoint the cellular changes underlying the enhanced properties, the total protein composition and metabolic features of genome-reduced Bacillus strains were investigated. This revealed that the new strains have a higher capacity for the synthesis and secretion of proteins, while suffering less from the detrimental effects of so-called ‘protein production stress’. The enhanced protein secretion allows for easy downstream product purification. Moreover, some of the genome-minimised strains show enhanced fermentation properties. To conclude, the results described in this thesis highlight the great potential of genome engineering to develop new-generation bacterial cell factories for industrial applications that satisfy the ever-increasing demands for high quality enzymes and pharmaceutical proteins.