**4. Conclusions**

The results of the present study indicate the successful development of a novel cheese whey valorization approach within the concept of circular bioeconomy. More specifically, a two-stage operation was established to generate crude enzymatic consortia via fungal solid state fermentations with *A. awamori*. Fermentation conditions were optimized and a novel biocatalyst was effectively secreted, and subsequently implemented to hydrolyze whey lactose formulating a nutrient substrate for fermentative bioconversions. BC production was conceptualized as a transitional compound for subsequent functional food formulations, along with the protein fraction to complement sustainability and circularity of the process.

**Author Contributions:** Conceptualization, N.K.; methodology, I.K.L., V.K., A.P., E.E. and N.K.; investigation, I.K.L., V.K., A.S. and D.L.; resources, A.P., E.E. and N.K.; writing—original draft preparation, I.K.L., A.P. and V.K.; writing—review and editing, I.K.L., V.K. and N.K.; supervision, A.P. and N.K.; project administration, N.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study is part of the project "Valorization of cheese dairy waste for the production of high added-value products" (MIS 5007020) which is implemented under the Action "Targeted Actions to Promote Research and Technology in Areas of Regional Specialization and New Competitive Areas in International Level", funded by the Operational Programme "Ionian Islands 2014–2020" and co-financed by Greece and the European Union (European Regional Development Fund).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data sharing not applicable.

**Acknowledgments:** We acknowledge A. Koutinas (Agricultural University of Athens, Greece) for kindly providing the *A. awamori* strain, as well as M.N. Efthymiou and F. Sereti for the laboratory assistance.

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