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Highlights-PLA nanoparticles loaded with Thymol were prepared for the first time.-The PLA was found to be the key variable in optimizing the nanoparticle preparation.-The nanoparticles exhibited a high storage stability over a wide range of pHs.-The antimicrobial activity of the nanoparticles was tested on apple pieces.

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Acid whey causes a major disposal problem for the dairy industry due to its low pH and high salt concentration. Lactobionic acid (LBA) production by whey fermentation is an inexpensive process. The goal of this work was to employ acid whey for LBA production. Acid whey was fermented in a bioreactor, adding Pseudomonas taetrolens LMG 2336 at 30°C and 6.5 pH, with 1.5-Lpm oxygen aeration and 350-rpm agitation. Three fermentation tests were carried out with a different amount of inoculum (10%, 30% and 10% three times within 24 h). Results indicated that repeatedly adding P. taetrolens inoculum to the acid whey substrate allows a complete lactose conversion into LBA, while the lactose oxidation process was insufficient in the sample where the inoculum was only added at the beginning of the fermentation process (only 29.7% LBA production with 10% inoculum). The physiological heterogeneity of P. taetrolens was determined by multiparametric flow cytometry, and results showed that there was a phenotypic adaptation of the microorganism due to the changes observed in its heterogeneity and physiological state. The results achieved will help to recycle acid whey for value-added product production such as LBA production.

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Cheese whey, one of the most abundant by-products of the dairy industry, causes economic losses and pollution problems. In this study, deproteinised sweet whey was fermented by Pseudomonas taetrolens LMG 2336 to produce a prebiotic compound (lactobionic acid, LBA). Endotoxins produced by these microorganisms were successfully removed using microfiltration techniques, allowing the fermented whey permeate to be used in the food industry. The fermented whey permeate was used to develop prebiotic edible films by adding two different concentrations of gelatine (0.45 and 0.9 g gelatine g−1 LBA; LBA45 and LBA90). Furthermore, Lactobacillus plantarum CECT 9567 was added as a probiotic microorganism (LP45 and LP90), creating films containing both a prebiotic and a probiotic. The mechanical properties, water solubility, light transmittance, colour, and microstructure of the films were fully characterised. Additionally, the LBA and probiotic concentration in LP45 and LP90 were monitored under storage conditions. The strength and water solubility of the films were affected by the presence of LBA, and though all these films were homogeneous, they were slightly opaque. In LP45 and LP90, the presence of LBA as a prebiotic improved the viability of L. plantarum during cold storage, compared to the control. Therefore, these films could be used in the food industry to coat different foodstuffs to obtain functional products.