Making Enzymes With Fungus
Trichoderma reesei Rut C-30 is a branched cellulase producing fungus that has been mutated to ensure continuous cellulase enzyme production. These cellulase enzymes are important for the paper and clothing industry to make smooth fabric surfaces. In the future, a very low cost cellulase enzyme can be used to digest waste biomass (leaves, tree branches, grasses, etc.) into simple sugars (glucose) for fermentation. We can ferment yeast with these sugars to make alcohol. If the alcohol is cheap enough, we can burn it for energy – or drink it.
In the wild, the fungus (Trichoderma) will grow on a solid substrate (a cotton tent, dead tree, grass, etc.). In the lab we grow the T. reesei in a submerged fermenter with waste milk sugars (lactose). We can control the nitrogen and carbon sources, pH, temperature, dissolved oxygen, and mixing. This highly controlled environment allows for daily sampling and accurate measurement of the growth, cellulase production, and food consumption. You can think of the Trichoderma as small factories that produce the enzyme from sugar and proteins.
The goal of my PhD work was to convince the T. reesei to grow into a compact pellet and then stop growing and keep making enzyme for us. The premise of this research has been published in Enzyme and Microbial Technology. Basically, certain surfactants can be used, under specific growth conditions, to make the cells grow into a pellet. These pellets can be harvested by settling and then reused to make more enzyme. The main focus of my current work is controlling the growth, understanding how to keep the pellet for long-term fermentations, and what cost advantages can be realized with this method. The full work appears in my PhD dissertation… and should be public soon.