**5. Conclusions**

The purity and the recovery of both glucan and lignin from OPEFB could be obtained through a series of sequential steps of ethanol organosolv pretreatment. Lignin purity and recovery of ca. 71% and 65%, respectively, were obtained, opening the potential for higher-value applications. Furthermore, high-purity glucan fraction was also obtained that showed ca. 94% digestibility within 18 h of enzymatic treatment. The study shows that high delignification of OPEFB (of ca. 90%) and consequent recovery of high-purity lignin- and glucan-rich fractions can be obtained at remarkably lower acid concentration (0.07%) in comparison to previous studies within the area as result of an increase in the solid loading used.

**Author Contributions:** Conceptualization, R.M., W.B., C.N., and M.J.T.; methodology, K.M., M.J.T. and J.A.F.; formal analysis, K.M. and J.A.F.; investigation, K.M. and J.A.F.; writing—original draft preparation, K.M. and J.A.F.; writing—review and editing, M.J.T., R.M., W.B., C.N.; supervision, R.M., W.B., C.N., J.A.F., and M.J.T.; project administration, R.M., W.B., C.N., and M.J.T.; funding acquisition, R.M., C.N., and M.J.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Program Menuju Doktor Sarjana Unggul (PMDSU) Batch III of the Ministry of Research, Technology and Higher Education of the Republic of Indonesia (Kemenristekdikti RI) (grant number 5844/DUN1.DITLIT/DIT-LIT7LT/2018) and Swedish Reseach Council (VR).

**Acknowledgments:** The authors would like to acknowledge PMDSU Scholarship from the Ministry of Research, Technology and Higher Education, Indonesia and Swedish Reseach Council (VR) for the administrative and funding support.

**Conflicts of Interest:** The authors declare no conflict of interest.
