**4. Conclusions**

To accelerate the use of lignocellulosic feedstocks in fermentative processes it is crucial to select the right biomass for the desired process. This study demonstrated that bleached cellulose pulp is a potential candidate for use on the production of itaconic acid by fermentation since it is highly rich in cellulose that can easily be converted into glucose by enzymatic hydrolysis without requiring a previous step of pretreatment. This is in fact an important aspect contributing to the economic feasibility of the fermentation process for itaconic acid production, since pretreatment is usually a very energy-intensive step and impacts significantly on the final costs of the process and the product.

Other important findings of this study were related to the fermentation of the glucose-rich hydrolysate produced from cellulose pulp. Due to the presence of glucose as the main component, no lignin or sugar degradation products in the medium that could negatively affect the strain performance, the only concern is to establish conditions that can direct the metabolism of the strain towards the product formation with minimum use of carbon source for biomass growth. Within this study, it was demonstrated that the C:N ratio and the oxygen availability play important roles in the production of itaconic acid by *A. terreus* from cellulose pulp hydrolysate and should be carefully considered in subsequent studies in a bioreactor setup. Increasing the initial carbon source was also a strategy able to result in better production of itaconic acid and should be further explored taking into account the use of an appropriate C:N ratio during the experiments. Finally, sterilization of the hydrolysate before fermentation is a required step that can also affect the medium composition leading to an unbalance in the C:N ratio, being the sterilization by membrane filtration the most recommended method to result in a better fermentation performance.

**Author Contributions:** Conceptualization, S.I.M.; Methodology, S.I.M., G.D., and C.K.Y.; Investigation, M.C. and P.D.; Resources: S.I.M.; Data curation, A.A.J.K., M.C., P.D., G.D., C.K.Y., and S.I.M.; Writing—original draft preparation, A.A.J.K., G.D., and S.I.M.; Writing—review and editing, S.I.M.; Supervision, S.I.M., G.D. and C.K.Y.; Project administration: S.I.M.; Funding Acquisition, S.I.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Novo Nordisk Foundation, Denmark (grant number NNF10CC1016517).

**Acknowledgments:** Special thanks to Suzano S/A (Brazil) for supplying the cellulose pulp used in this research, and to Novozymes (Denmark) for providing the enzyme concentrate Cellic® CTec2.

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