Maximizing the utilization of all biomass components is essential for ensuring the long-term sustainability of biorefinery. In this presentation, we report the recent investigation of lignin properties obtained during microwave-assisted deep eutectic solvents (MW-DES) fractionation from spruce heartwood (HW) and sapwood (SW) before and after preliminary hot water extraction (HWE), i.e. from residue heartwood (RHW) and residue sapwood (RSW), respectively. It was found that whether it is pretreated by HWE or directly treated with DES, both DES lignins exhibit high phenolic hydroxyl content in the amount of 2.59/2.73 mmol/g (HW/SW) and 2.54/2.74 mmol/g (RHW/RSW) [1]. The phenolic hydroxyl groups are key functional groups enabling further molecular functionalization for specialized applications. In addition, HWE pretreatment of both HW and SW before MW-DES extraction gives an opportunity to obtain the lignin with the purity of 88% and the carbohydrate content below 0.5%. All solid residues, i.e. cellulose-rich fractions remaining after MW-DES fractionation were successfully used to make regenerated cellulose fibres through wet spinning. The residual cellulose-rich fractions exhibited varying molar mass and viscosity depending on the treatment protocol. The properties of the regenerated cellulose fibers were assessed and compared. The results of this comprehensive study offer a potential pathway for biorefinery and further contribution to the advancement of the sustainable economy.