**4. Conclusions**

Biodegradable antioxidant bilayer films were successfully developed by using an outer layer based on a compression-molded PHVB/PBAT-based material and an inner antioxidant layer based on plasticized PLA-PHB electrospun fibers loaded with catechin. Plasticized electrospun PLA-PHB fibers encapsulating catechin were successfully obtained by means of the electrospinning technique. The addition of 1 wt% of Cat was enough to improve the mechanical properties of the electrospun mats, while 3 wt% produced some structural defects reducing the mechanical performance of the final materials. The obtained mats were used as inner layers for PHBV-based bilayer systems, where a PHBV/PBAT-based material provided the mechanical resistance to the final packaging film. The bilayer systems presented antioxidant activity in a fatty food simulant showing their potential as active food packaging materials. Meanwhile, they were totally disintegrated under composting conditions highlighting their potential application in the sustainable food packaging industry.

**Author Contributions:** M.P.A. and L.P. conceived and designed the paper structure. M.P.A. and A.D.G. performed the experiments, measurements and data analysis. M.P.A. and L.P. wrote the manuscript. S.F. synthesized the O.L.A. plasticizer and co-wrote the manuscript. D.L. supervises the rheological measurements and co-wrote the manuscript. L.P. and D.L. performed the project administration.

**Funding:** This research was funded by the Ministerio de Ciencia, Innovación y Universidades (MICINN, Spain), the Agencia Nacional de Investigación (AEI, Spain) and el Fondo Europeo de Desarrollo Regional (FEDER, EU), project number MAT2017-88123-P. M.P. Arrieta thanks Universidad Complutense de Madrid for her postdoctoral contract (Ayuda posdoctoral de formación en docencia e investigación en los Departamentos de la UCM). L. Peponi thanks MICINN for her "Ramon y Cajal" contract RYC-2014-15595.

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