Kinetics of Aspergillus niger cellulase inhibition by reducing sugar produced by the hydrolysis of carboxymethylcellulose

Hydrolysis of two types of cellulose, namely, totally amorphous Carboxymethyl-cellulose (CMC) and highly crystalline wood shavings, by Aspergillus niger cellulase was studied in a stirred batch reactor at 50°C. Two kinetic models were devised to predict the rate of reducing sugar production assuming competitive and non-competitive product inhibition of the enzyme. The applicability of the models was tested by comparing experimental results with those predicted by the models. Both models followed the experimental data fairly well, giving standard deviation of 13.3 and 7.9 for the competitive and the non-competitive inhibition models, respectively. However the non-competitive inhibition model showed more realistic behaviour than the non-competitive model and represented better the experimental data. The significance of crystallinity was determined by comparing the production of reducing sugar from wood shavings to the production from CMC. At same initial substrate concentration, it was found that the production of reducing sugar ceased at much shorter times for wood shavings in comparison to that for CMC.