Lipase A from Candida antarctica (CalA) and β-glucosidase from Thermotoga maritima (bgl) were covalently co-immobilized onto the surface of chitosan-coated magnetic nanoparticles (CS-MNPs). Several parameters regarding the co-immobilization procedure (glutaraldehyde concentration, incubation time, CS-MNPs to enzyme mass ratio and bgl to CalA mass ratio) were evaluated and optimized. The developed nanobiocatalyst was characterized by various spectroscopic techniques. Biochemical parameters such as kinetic constants and thermal stability were also evaluated. The nanobiocatalytic system revealed an increase in the Km constant followed by a decrease in Vmax value compared with the native enzymes, while a significant increase (>5-fold higher) of the thermal stability of the immobilized CalA, both in individual and in co-immobilized form, was observed after 24 h incubation at 60 °C. Finally, the nanobiocatalyst was efficiently applied for the bioconversion of oleuropein to hydroxytyrosol, one of the most powerful naturally derived antioxidants, and it could be recycled for up to 10 reaction cycles (240 h of constant operation) at 60 °C, retaining more than 50% of its initial activity.

A series of polymers, including chitosan (CS), carboxymethylcellulose (CMC) and a chitosan–gelatin (CS–GEL) hybrid polymer, were functionalized with ferulic acid (FA) derived from the enzymatic treatment of arabinoxylan through the synergistic action of two enzymes, namely, xylanase and feruloyl esterase. Subsequently, the ferulic acid served as the substrate for laccase from Agaricus bisporus (AbL) in order to enzymatically functionalize the above-mentioned polymers. The successful grafting of the oxidized ferulic acid products onto the different polymers was confirmed through ultraviolet–visible (UV–Vis) spectroscopy, attenuated total reflectance (ATR) spectroscopy, scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) spectroscopy. Additionally, an enhancement of the antioxidant properties of the functionalized polymers was observed according to the DDPH and ABTS protocols. Finally, the modified polymers exhibited strong antimicrobial activity against bacterial populations of Escherichia coli BL21DE3 strain, suggesting their potential application in pharmaceutical, cosmeceutical and food industries.

Smart packaging of food products is a new promising technology aiming to the preservation of consumer’s health and safety while prolonging the products’ self-life in transport and mass storage. Smart packaging can be applied by using chemical and/or biological sensors for monitoring indicators associated with bacterial growth and spoilage, as well as pathogen contamination. Poultry meat is a nutrient-rich matrix which supports the growth of various micro-organisms and the extended storage time can allow the proliferation of different microbial species on meat surfaces. The nature of the packaging approaches and storage factors can dictate the nature of the spoilage that transpires, with respect to the dominant microflora of the end-product. In the present study an innovative approach is explored for the development of cost-effective 3D-printed biosensors for monitoring known indicators associated with bacterial growth and spoilage in poultry meat. Spoilage was also independently measured using MSI and FT-IR spectroscopic methods. The development of a protocol for pathogen screening was also investigated with real-time polymerase chain reactions (qPCR).