Biocontrol Potential of Poly(3-hydroxybutyrate) Fibers Functionalized with Chitooligosaccharide/Bacillus subtilis Using Electrospinning and Electrospraying

Sustainable agriculture increasingly relies on biocontrol agents as eco-friendly solutions to combat plant diseases while improving soil health. In this context, species of the genus <i>Bacillus</i>, particularly <i>Bacillus subtilis</i>, have shown promise as effective biocontrol agents for plant diseases. This study demonstrates the successful fabrication of biohybrid materials by decorating electrospun poly(3-hydroxybutyrate) (PHB) fibers with electrosprayed chitooligosaccharide (COS) and <i>Bacillus subtilis</i> using simultaneous electrospinning and electrospraying. During electrospraying, COS formed a uniform film over the PHB fibers, serving as both an adhesive and a protective coating that maintained the viability and functionality of the embedded bacteria. SEM confirmed that bacterial spores were uniformly spread across the COS-coated biopolymer fibers. ATR-FTIR spectroscopy verified the successful deposition of COS on the fibers, while mechanical assay demonstrated enhancement in mechanical characteristics after the COS film formation on the PHB fibers compared to uncoated PHB. In addition, COS improved the wetting properties of the fibrous PHB material, creating a favorable environment for bacterial growth and development. Microbiological tests showed that the embedded <i>B. subtilis</i> remained viable and proliferated normally after 48 h under suitable conditions at 28 °C on agar medium. Furthermore, the biohybrid COS/<i>B. subtilis</i>-<i>on</i>-PHB materials also effectively inhibited the growth of pathogenic fungi, including species of <i>Alternaria</i> and <i>Fusarium</i>. These findings highlight the potential of dual electrospinning/electrospraying techniques for the fabrication of eco-friendly biocontrol formulations. The integration of COS coatings with <i>B. subtilis</i> provides a promising approach for sustainable agriculture by combining enhanced material properties with effective antifungal activity.