5.5% (w/w) were examined at 40 U/g of laccase for 24 h. 2.5%
(w/w) and 3.5% (w/w) PCA concentration resulted in 11.6% and
30.0% biografting of coconut fibers due to the enzymatic copoly-
merization of lignin with PCA. There was an increase in the rate
of reaction with the increase in phenol concentration and maxi-
mum grafting (52.3%) was obtained at 4.5% (w/w) [CF-g-PCA(1)]
(Fig. 2a). Increased biografting with an increase in PCA concen-
tration was due to the availability of a large number of phenoxy
radicals. With the further increase in the PCA concentration, per-
centage biografting was decreased due to unavailability of enzyme
to form enzyme–substrate complex because of saturation point.
Laccase concentration was varied from 20 U/g to 80 U/g at an
optimized concentration of PCA for 24 h to analyze the effect of
enzyme concentration on biografting. Percentage biografting was
increased with increase in laccase concentration from 20 U/g (20%)
to 40 U/g (51.8%). Percentage biografting was decreased with fur-
ther increase in laccase concentration (Fig. 2b). 40 U/g of laccase
was the optimized concentration for maximum biografted sample,
i.e. CF-g-PCA(2) because a small amount of enzyme can catalyze the
reaction to its maximum. The incubation period was varied from
12 h to 36 h at optimized PCA and laccase concentration. 47.6%,
51.8% and 49.1% biografting was observed at 12 h, 24 h and 36 h,
respectively. Biografting was increased initially with an increase in
incubation time due to the formation of more enzyme–substrate
complex. Maximum percentage grafting (51.8%) was obtained at
an incubation period of 24 h [CF-g-PCA(3)] (Fig. 2c). Percentage
biografting was increased with an increase in incubation time due
to the accumulation of biografting at a longer incubation period.
After 24 h, the laccase-mediated depolymerization turned to be
predominant. Maximum grafted sample i.e. CF-g-PCA(3) was cho-
sen for the study of antibacterial and hydrophobic properties.