Surface Modification of Cellulose Acetate with Cutinase and ...

Effect of the Agitation on the Adsorption and Hydrolytic Efficiency of Cutinases on Polyethylene Terephthalate fibres
(600 nm) as an average of five readings. The control samples were incubated in
phosphate buffer solution.
2.6. Protein adsorption and desorption
The remaining protein in the enzymatic treatment solution for different incubation
periods was measured to study the adsorption and desorption phenomena (Araújo et al.,
2007). For this adsorption/desorption studies the protein in solution was determined by
the Bradford method using bovine serum albumin (BSA) as standard (Bradford, 1976).
Different time samples of enzymatic treatment solution were measured (0, 1, 2, 3, 4 and
5 h). After 5 h of incubation, the enzymatic treatment solution was diluted (1:2) with the
same previously specified phosphate buffer and the mixture was subsequent incubated
for another 60 minutes, with the same agitation and temperature conditions, to verify the
desorption phenomena. Values had a standard deviation below 9%. The percentage of
adsorption was calculated by the following expressions as described in literature
(Azevedo et al., 2000):
A − B
× 100
% adsorption = A
D − C
× 100
% desorption = A
Where: A – initial protein concentration (at 0 h); B – protein concentration at time t (1,
2, 3, 4 and 5 h); C – dilution (dilution 1:2 with buffer solution); D – final protein
concentration (after the dilution and 60 more minutes of incubation).
3. Results and Discussion
The formation of terephthalic acid (TPA) and the protein adsorption for the two studied
cutinases, with a low agitation level (shaker bath, 2A) and strong agitation level
(Rotawash, 2B), is shown in figure 1. In table 1 the values of percentage of protein
adsorbed for the different incubation periods are shown for both modes of mechanical
agitation.
(1)
(2)
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