Influence of agitation on the morphology of Trichoderma reesei and its correlation with the protein production

Abstract

In search for a more sustainable source of fuel, bioethanol has been considered as a primary candidate to achieve this objective. To overcome the competition between food and fuel that is currently developing, bioethanol from lignocellulosic source especially from agricultural residues instead than from corn or sugar cane should be favoured. To hydrolyze the cellulose into fermentable sugars so that they can be used to produce ethanol, cellulase enzyme must be produced efficiently and economically. The objective of the present research is to contribute toward this goal and, in particular, to study the effect of agitation on cellulase production and on the morphology of Trichoderma reesei, the microorganism used to produce this enzyme. A series of eight experiments were conducted in a stirred tank bioreactor (STB) and in a reciprocating plate bioreactor (RPB) at various agitation speeds ranging from 200 to 500 RPM and 0.25 to 1.0 Hz, respectively. For each experiment, image analysis was used to determine changes in morphology of Trichoderma reesei throughout the fermentation. The protein productivity was correlated to one morphological parameter, the hyphal growth unit. It was found that in the STB, low agitation (200 and 300 RPM) resulted in lower protein productivity whereas high agitation (500 RPM) was detrimental to the microorganisms. The optimal speed of agitation was determined to be 400 RPM where the highest productivity was achieved. In the RPB, higher agitation speed resulted in a higher productivity and the highest productivity was achieved at 1.0 Hz. As a second objective, a quick and economical off line method using conventional home blood glucose monitors was developed to measure the glucose concentration during the fungal fermentation of T. reesei. Two monitors, OneTouch Ultra and Ascensia Contour, were tested and implemented for the monitoring of the glucose concentration during both flask and bioreactor fermentations of T. reesei. OneTouch monitor was found to be more suitable.