Lactic acid bacteria (LAB) have been shown to prevent the growth and activity of several postharvest pathogen fungi in fruit and vegetables because of their ability to produce antimicrobial metabolites. Edible coatings (ECs) can be used as carriers of LAB and could provide an alternative natural preservation method. The effectiveness of Lactobacillus plantarum against fungal decay on grapes applied together with EC was studied. Different formulations with or without L. plantarum were considered, using pregelatinized potato starch (PS) or sodium caseinate (NaC) as main components of the coating matrices. In some of the formulations, oleic acid (OA) was added as a surfactant. The population dynamics of the bacterium and its ability to control fungal decay were studied together with the assessment of fruit quality. NaC-based formulations improved survival of L. plantarum on fruit surface after 7 days of storage in comparison with a water control. On the other hand, L. plantarum in PS-based formulation without OA reduced Botrytis incidence more than when applied in NaC formulation or in water. Coatings had little effect on berry quality (weight, color, firmness, and soluble solids content) of grapes throughout storage, although some of the coated samples maintained acidity and maturity index during storage better than others. Therefore, LAB applied in ECs could provide a viable biocontrol method for postharvest disease in grapes.

The in-field performance of microbial biocontrol agents (BCAs) against fungal pathogens in fruit is subject to considerable variability due to their sensitivity to both adverse environmental conditions and their fluctuations. Therefore, to achieve an adequate development and implementation of biological agent-based products, it is necessary to improve their resistance and ability to control fungal diseases under a wide range of conditions. In this review, an overview of the latest strategies for the enhancement of the action of BCAs is given. The combination of the antagonists with edible polymers able to form coatings is one of the approaches with the greatest potential and it is analysed in depth. This formulation approach of biocontrol products, including adequate microbial protectants, can yield stable products with high microbial viability, ready for field applications, with improved adherence and survival of the BCA once applied in plant. The most recent studies into this field are reviewed and summarised.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has gained attention as a possible substitute for conventional polymers that could be integrated into the organic recycling system. Biocomposites with 15% of pure cellulose (TC) and woodflour (WF) were prepared to analyze the role of lignin on their compostability (58 °C) by tracking the mass loss, CO₂ evolution, and the microbial population. Realistic dimensions for typical plastic products (400 µm films), as well as their service performance (thermal stability, rheology), were taken into account in this hybrid study. WF showed lower adhesion with the polymer than TC and favored PHBV thermal degradation during processing, also affecting its rheological behavior. Although all materials disintegrated in 45 days and mineralized in less than 60 days, lignin from woodflour was found to slow down the bioassimilation of PHBV/WF by limiting the access of enzymes and water to easier degradable cellulose and polymer matrix. According to the highest and the lowest weight loss rates, TC incorporation allowed for higher mesophilic bacterial and fungal counts, while WF seemed to hinder fungal growth. At the initial steps, fungi and yeasts seem to be key factors in facilitating the later metabolization of the materials by bacteria.

Biodegradable polymers offer a potential solution to marine pollution caused by plastic waste. The marine biofilms that formed on the surfaces of poly(lactide acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied. Bioplastics were exposed for 6 months to marine conditions in the Mediterranean Sea, and the biofilms that formed on their surfaces were assessed. The presence of specific PLA and PHBV degraders was also studied. PHBV showed extensive areas with microbial accumulations and this led to higher microbial surface densities than PLA (4.75 vs. 5.16 log CFU/cm²). Both polymers’ surfaces showed a wide variety of microbial structures, including bacteria, fungi, unicellular algae and choanoflagellates. A high bacterial diversity was observed, with differences between the two polymers, particularly at the phylum level, with over 70% of bacteria affiliated to three phyla. Differences in metagenome functions were also detected, revealing a higher presence of proteins involved in PHBV biodegradation in PHBV biofilms. Four bacterial isolates belonging to the Proteobacteria class were identified as PHBV degraders, demonstrating the presence of species involved in the biodegradation of this polymer in seawater. No PLA degraders were detected, confirming its low biodegradability in marine environments. This was a pilot study to establish a baseline for further studies aimed at comprehending the marine biodegradation of biopolymers.