Fig. 2.

Chi18H8 expression levels in insoluble fractions from E. coli BL21 Star™(DE3)/pET24b(+)::chi18H8 grown in LB medium. Protein expression was induced at the early exponential phase of growth by adding 0.4 mM IPTG, cells were then incubated at 37, 25 or 20 °C, respectively, and harvested after 0, 1, 2, 4 or 24 h. Chi18H8 production (mg/g cell) was determined by densitometric analysis of SDS-PAGE; chitinase activity (U/g cell) was measured fluorimetrically using 4-MU-(GlcNAc)₂ as a substrate. The values represent the mean of three experiments. Standard error never exceeded 5%