For instance, in the case of ozone the presence of lignin implies an inevitable depolymerisation of polysaccharides throughout the in-situ generation of free radicals, rather than by a direct attack of ozone ). The MMD of the Ko-ZEo series in Figure show the apparition of a shoulder in the high-M r end with increasing ozone charge. This is foreshadowing the presence of a C High-Mr peak. But unlike that of the Fb-ZEo pulps, the peak is now contracting towards lower Mw values with increasing ozone dose. The similarity with the effect described for the Fb-H series (Figure ) may confirm that the contraction of the C High-Mr peak is a phenomenon attributed to the cleavage of cellulose crystallites. Indeed, this contraction of the high-Mr end was also observed for Fb-Ccell pulps (Figure ), with Celluclast® having the ability of attacking crystalline regions . We assume that this high M r cellulose is mostly present in the fibre outer parts (P+S1, S3, outer S2) as ozone bleaching follows a shrinking-core reaction model , which was further exemplified by the macrofibrillation index of Ko increasing with the ozone charge (Table ). Alternatively, "Z alk ", an ozone treatment in alkaline conditions was performed (pH 12.5), followed by alkaline extraction E and illustrated in Figure . At this pH, the oxidation mechanisms taking place are almost exclusively due to free radicals issued from the rapid ozone decomposition. During the Z alk 3)E treatment the very reactive radicals unselectively affected polysaccharides in their immediate vicinity. The resulting MMD was somehow similar to that of Ko-Z(2)Eo sample but seemed to hold longer cellulose chains. In fact, the Z alk E treatment produced a pulp with the highest Đ M (C) value by far in this work vs. maximum 2.8 for other samples, see Supplementary file for more details). This result is rather surprising since one could expect a more homogeneous degradation such as HOCl oxidation, due to the high fibre swelling at alkaline pH and the presence of radicals that should provoke random chain scissions. A possible explanation is that lignin being a good radical scavenger the C High-Mr peak in Ko-Z alk 3)E would, in this case, represent protected cellulose chains which are adjacent to residual lignin in Ko rather than cellulose located in highly organised domains. Interestingly, the H treatment degraded less the low-M r polysaccharides on the Odelignified Ko pulp than on fully-bleached Fb pulp (cf. Figure ), a possible consequence of the oxidation quenching effect of lignin.