The effects on fibre surface produced by the laccase-mediator system on softwood sulphite fibres were analysed in terms of surface crystallinity using thermogravimetric analysis. The starting pulp presented low content of lignin and hemicelluloses and these characteristics were clearly reflected on TGA graphs, indicating a clean and crystalline surface. Unbleached sulphite pulps were subjected to a biobleaching process using the well-know laccase-mediator system (LMS). From all studied mediators, violuric acid, VA, was the most efficient biobleaching compound. By contrast, HBT also provided a good delignification but affected negatively the fibre “surface”. The natural mediators, SA and PCA were not grafted on sulphite pulp unlike what have been observed with other raw materials. These observations led to the development of an extended biobleaching sequence named LVAQPo, using a laccase from Trametes villosa in combination with VA as a mediator. The characterization of treated pulp in terms of dissolving pulp characteristics showed that this enzymatic sequence could satisfy the market-like requirements. In addition, TGA results showed that the introduction of an enzymatic stage let to reduce the adverse effect caused by a hydrogen peroxide treatment in terms of pulp crystallinity