Sunday, April 29, 2007

Temperature and pH stability of Trichoderma reesei RUT C30 cellulolytic complex

Ayla Santana Silva, Felipe Moura Knopp, and Elba Bon. Biochemistry - Chemistry Institute, Federal University of Rio de Janeiro, Instituto de Quimica, sala 539 - Cidade Universitaria, Ilha do Fundao, Rio de Janeiro, Brazil

In 2005, Brazil imported US$ 1million (204.2 tons) of cellulases, which corresponded to 3% of imported enzymes. Cellulases have been utilized in food, animal feeds, textile production and laundering, having potential application in the production of ethanol from biomass. The industrial use of cellulolitic enzymes requires the knowledge of its profile for temperature and pH activity and stability that allow the design of adequate conditions for each process. This study evaluated the use of low-cost substrates (wheat brain, dried distilled grains (DDG) and sugar cane bagasse (SCB), to induce the cellulase complex production by Thichoderma reesei RUTC30. Growth medium presented 3.0% of the aforementioned substrates and 0.6% yeast extract, 0.6% (v/v) corn steep liquor plus salts. The results showed that wheat bran provided better production of cellulolytic enzymes, corresponding to 26700 UI/L CMCases, 1200 UI/L FPases and 460 UI/L b-glicosidase. These results were 2-fold higher than that obtained on SCB or DDG. The supernatant from optimized conditions was used to evaluate the effect of the pH and temperature on the activities. The optimum activity was found to be at pH 4,8 and in the range of 60°C-70ºC. Enzymes were stable at 50ºC, as 80% of the activities were retained after 24h of incubation and at 60ºC as 65% of the initial activity was measured after 5h of incubation. Enzymes were stable for 24h in the pH range 4,0-4,8 (50ºC). These results, besides confirming T.reesei RUTC30 as a cellulolytic strain points out to the temperature activity and stability of its enzymes.