Chitinase activity was assessed using a colorimetric method to
detect N-acetyl-d-glucosamine (NAG) produced by the combined
hydrolytic action of chitinase and -glucuronidase (Sigma–Aldrich)
on non-radioactive colloidal chitin (Molano et al., 1977) used as
substrate (Boller, 1992; Reissig et al., 1995). The concentration
of NAG was determined by spectrophotometry at 585 nm against
a standard curve of NAG (Sigma–Aldrich), ranging from 100 to
600 mM. The chitinase activity was expressed in nanokatal per milligram of protein (nkat/mgP). One nkat is equivalent to 1.0 nmol of
NAG released/mL/s, under the assay conditions