**4. Conclusions**

The present findings demonstrate that the biosurfactant produced by *Bacillus cereus* UCP 1615 grown in a medium containing waste frying oil has the potential for use as a bioemulsifier in food systems because it has been shown to be an effective emulsifying agent for various vegetable oils. The addition of the biosurfactant did not drastically affect the final product as the biosurfactant-containing formulations showed energetic and physical characteristics similar to those of the standard formulation, indicating the feasibility of applying this biomolecule in the formulation of cookies. The biosurfactant was non-toxic, which suggested its safe use, and had a considerable antioxidant activity. The biosurfactant demonstrated promising results as an ingredient for a flour-based product in terms of the physical, physicochemical and textural properties of the cookies formulated. The biosurfactant also ensured a good preservation of the cookies. Based on the results obtained in this study, the bacterial surfactant could be tested in other products as a green additive in the food industry. However, further studies are needed to enhance the economic viability of the production of this microbial surfactant on an industrial scale for its use as an emulsifier in food.

**Author Contributions:** Conceptualization, L.A.S.; methodology, I.J.B.D., B.G.R. and J.S.A.; validation, L.A.S.; A.C. and R.D.R.; formal analysis, L.A.S.; investigation, I.J.B.D. and B.G.R.; resources, L.A.S.; data curation, I.J.B.D., B.G.R. and R.D.R.; writing—original draft preparation, I.J.B.D. and R.D.R.; writing—review and editing, L.A.S. and A.C.; visualization, L.A.S. and A.C.; supervision, L.A.S.; project administration, L.A.S.; funding acquisition, L.A.S. and R.D.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was funded by the Brazilian fostering agencies Fundação de Apoio à Ciência e Tecnologia do Estado de Pernambuco (FACEPE), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) (Finance Code 001).

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors are grateful to the laboratories of Universidade Católica de Pernambuco (UNICAP), Universidade Federal de Pernambuco (UFPE) and Instituto Avançado de Tecnologia e Inovação (IATI), Brazil.

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