**4. Conclusions**

**4. Conclusions** Overall, the present study provides a small local circular economy example in which one of the most abundant industrial wastes produced by small and medium regional companies could be easily valorized by configuring processes that generate value-added Overall, the present study provides a small local circular economy example in which one of the most abundant industrial wastes produced by small and medium regional companies could be easily valorized by configuring processes that generate value-added products using a bio-refining concept.

In particular, the implementation of a membrane-based process involving a ultrafiltration and a nanofiltration step was demonstrated to be sufficient to reduce the

organic load of whey resulting in a clean and reusable effluent.

products using a bio-refining concept.

In particular, the implementation of a membrane-based process involving a ultrafiltration and a nanofiltration step was demonstrated to be sufficient to reduce the organic load of whey resulting in a clean and reusable effluent.

Maybe even more importantly, this downstream process generates fractions differentially enriched with potentially interesting compounds. The concentrated UF retentate was investigated here and demonstrated (i) to be by itself a sufficient source of sugars and proteins to support the growth of a probiotic strain with known biomedical applications, and (ii) to stimulate epidermis (keratinocyte) regeneration and therefore meaning potential applicability as an ingredient in skincare products.

**Author Contributions:** C.S. conceived the study; D.C. and C.S. drafted the manuscript; A.A. conducted downstream processes; S.D. conducted bottle and fermentation experiments; A.D. conducted time-lapse experiments; R.F. conducted HPLC analyses. All authors have read and agreed to the published version of the manuscript.

**Funding:** The project was funded by MIUR PON03PE00060\_2 and PON BIONUTRA ARS01\_01166.

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data is contained within the article.

**Acknowledgments:** We kindly thank Maria D'Agostino and Michela Ventrone for helping with the time-lapse and fermentation experiments.

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