Production of xylanase activity by two different transformants overexpressing gene 77513. Transformants harboring the overexpression cassette as a single-copy (pMH15(S)) or as a double-copy (pMH15) were cultivated in shake flasks with lactose as a carbon source. Xylanase 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 xylanase activity, respectively.