Development of an active bio-based coating for corrugated cardboard with waterproofing and antimicrobial properties

The inherent perishability of high-value fresh horticultural commodities, such as strawberries, renders them highly susceptible to significant postharvest losses, underscoring a critical need for innovative preservation strategies that are aligned with circular economy principles. Therefore, this PhD thesis addresses this challenge by developing a sustainable, bio-based antimicrobial coating for cardboard, utilizing bacterial cellulose (BC) functionalized with natural essential oil compounds. Initially, high-yield Komagataeibacter strains were isolated and characterized for cellulose production. Then, to improve sustainability, cultivation process shifted from synthetic media to cost-effective agro-industrial byproducts. Among these, beet molasses emerged as optimal especially after process refinement, yielding BC with dense nanofibrillar structure and enhanced mechanical properties. Due to BC’s inherent hydrophilicity, surface modification was required. While conventional alkaline treatment proved ineffective, a green approach employing a deep eutectic solvent successfully increased the water contact angle to approximately 80°. Subsequently, functionalization was achieved using a patented blend of essential oil components (citral, hexanal, (E)-2-hexenal). The results showed that the casting of a BC slurry with direct incorporation of essential oils generated a porous matrix enabling sustained, biphasic release of active compounds over ten days at 15 °C. Final evaluation assessed BC-coated cardboard for strawberry packaging. Under ambient conditions, the active packaging system reduced fruit decay by 10% relative to control and demonstrated significant antimicrobial activity against enterobacteria. Nevertheless, its overall efficacy was constrained by suboptimal release kinetics, marginally inadequate to fully inhibit yeasts and moulds throughout the five-day storage period at 22 °C. This research establishes a robust framework for the sustainable production and functionalization of BC for active packaging applications. While demonstrating clear bioactivity, the findings underscore critical needs for optimizing release kinetics and hydrophobicity to translate this promising biomaterial into a commercially viable solution for mitigating food waste.