Cel7A hydrolysis of substrates with varying crystallinity

Esben Mortensen

Studenteropgave: Semesterprojekt

Abstrakt

In this experimental project the hydrolysis of cellulose substrates with varying crystallinity is catalysed by the processive cellobiohydrolase Cel7A and monitored real time by measuring the change of product concentration using an amperometric biosensor. The crystallinity variance is obtained by introducing a modified RAC method: using five different phosphate acid (PA) concentrations (77%, 79%, 81%, 83% and 85%) to modify the cellulose model Avicel. Data from two hydrolysis trials show a significant deviation in the hydrolysis rate between a pure Avicel sample and the five modified Avicel samples while no significant deviation among the five RAC-modified Avicel samples seems present. The crystallinity variance among all six samples is indicated by a Congo red dye adsorption study, which suggest that on a rough scale only three significantly crystallinity variances is obtained. Hereof sample 81, 83 and 85 (81, 83 and 85 % PA) represent the lowest crystallinity degree. These results compared with the hydrolysis results are equivocal as the literature prescribes the hydrolysis rate to increase with decreasing crystallinity (Hall, Bansal et al. 2010); (Lynd, Weimer et al. 2002). In the effort to understand this data a hypothesis is suggested on an arbitrary basis. This hypothesis suggests that the relatively low applied Cel7A concentration is exposed to an identical amorphous cellulose surface within all the modified Avicel samples and this cause the equivalent hydrolysis rates. It is important to make clear that this hypothesis has only been suggested and no thorough research on this area has been conducted. Finally an attempt of fitting the kinetic model, proposed by Praestgaard et al., to the hydrolysis data has been carried out. A large degree of noise and a lack of the ability of monitoring the so-called burst phase (an equivalent to the rate retardation) in the raw data have made the fitting impossible in this project.

UddannelserKemi, (Bachelor/kandidatuddannelse) Bachelor el. kandidat
SprogEngelsk
Udgivelsesdato22 jul. 2011

Emneord

  • Celullose crystillinity
  • Congo red
  • Cellulase kinetic
  • Cellulase
  • cellulose dying
  • Cel7a
  • Glucose Biosensor
  • RAC method