Production of cellulase and xylanase activity by the 77513 deletion strain. Del77513 was cultivated in shake flasks in lactose containing medium in parallel with the parental strain QM9414Δmus53. Enzyme activity was measured at four different time points (3, 5, 7 and 9 days). The values are means of three biological replicates. Error bars show the standard error of the mean. Panels A and B show the volumetric and production per biomass dry weight of total cellulase activity against MUL substrate, respectively. Panels C and D show the volumetric and production per biomass dry weight of xylanase activity, respectively. MUL, 4-methylumbelliferyl-β-D-lactoside.