One unit of cellobiase activity (CBU) was defined as the amount of enzyme
that produced 2 mmol of glucose per minute. The b-glucosidase was determined
using p-nitrophenyl-b-D-glucopyranoside (pNPGlc, Sigma) as a substrate at 50C for
10 min. Reactions were stopped by the addition of 1 M sodium carbonate, and the
released p-nitrophenol was detected by spectrometry at 410 nm. One unit of enzyme
activity was defined as the amount of enzyme that produced 1 mmol of pNP per
minute.