Monday, May 4, 2009
5-08
Cellulolytic enzyme production and response to pH and temperature by Trichoderma reesei
Trichoderma reesei has long been considered to be the most efficient producer of cellulases and it is currently used for production of commercial cellulolytic enzymes. However, further improvements in enzyme production are necessary to reduce costs sufficiently to make second generation bioethanol production economically feasible. T. reesei is well characterised on a molecular level and the genome has been sequenced, but little has been done to transfer this knowledge to process relevant conditions. Therefore, a physiological characterisation of T. reesei was conducted, focusing on the enzyme profile and levels produced under different process conditions.
T. reesei RutC30 was studied in a series of 4L batch fermentations at different temperatures (from 23°C to 33°C) and different pH values (from 3.0 to 6.0) using Avicel PH-101 (25 g/L) as carbon source. It was observed that germination time and growth rate increased greatly with increasing temperature, and the highest μmax of 0.25h-1 was reached at pH 4.5 and 33°C. In contrast, cellulolytic enzyme activity as well as total protein production was increased when the cultivation temperature was lowered. The maximum amount of filter paper activity units (FPU) was 7.36 FPU/ml reached after 180 h of cultivation at pH 4.5 and 23°C. Sporulation was observed in all cultivations at pH 6.0, which also foamed excessively. Analysis of the different fermentations by SDS-PAGE revealed that the same bands were seen for the enzymes secreted into the media, but that the concentrations of them (and thus the profile) were different when pH and temperature were changed.
T. reesei RutC30 was studied in a series of 4L batch fermentations at different temperatures (from 23°C to 33°C) and different pH values (from 3.0 to 6.0) using Avicel PH-101 (25 g/L) as carbon source. It was observed that germination time and growth rate increased greatly with increasing temperature, and the highest μmax of 0.25h-1 was reached at pH 4.5 and 33°C. In contrast, cellulolytic enzyme activity as well as total protein production was increased when the cultivation temperature was lowered. The maximum amount of filter paper activity units (FPU) was 7.36 FPU/ml reached after 180 h of cultivation at pH 4.5 and 23°C. Sporulation was observed in all cultivations at pH 6.0, which also foamed excessively. Analysis of the different fermentations by SDS-PAGE revealed that the same bands were seen for the enzymes secreted into the media, but that the concentrations of them (and thus the profile) were different when pH and temperature were changed.
PDF file