Cellulases production by <em>Aspergillus niger</em> and cellulase deactivation kinetic

Abstract

This work aimed to evaluate the kinetic for the cellulase production by Aspergillus niger and the deactivation kinetic of the cellulase enzymes. Cellulase were produced in three different batches using NaOH 4% (w v^-1) pre-treated sugarcane bagasse as the carbon source in the fermentation broth. The amount of the bagasse in each batch was 10, 50 and 100 g L^-1. The kinetic of the cellulase production was accomplished by periodically determining the cellulasic activity of the fermentation broth using pre-treated bagasse as the hydrolysis substrate. Changes in the pH also were determined. The cellulase deactivation kinetic was accomplished by periodically determining the cellulasic activity of the fermentation broth samples stored at 4°C and at -18ºC. One may conclude that Aspergillus niger produces cellulases when grown on medium with pretreated sugarcane bagasse as carbon source. The ideal time to collect the enzymatic broth was about seven days with maximum yield of 0.0013 U mL^-1∙h for the batch with 10 g L^-1, and 0.0018 U mL^-1∙h for the batches with 50 and 100 g L^-1. The cellulase complex does not suffer considerable deactivation when stored at -18°C (freezer) for 43 days, however, the activity drops by 40% within 48 hours when stored at 4°C (fridge).