Glucose oxidase - Catalase Mixture (eukaryote)

Background: In recent years there has been a surge in the number of commercially available lactose‐free variants of a wide variety of products. This presents an analytical challenge for the measurement of the residual lactose content in the presence of high levels of mono‐, di‐, and oligosaccharides. Results: In the current work, we describe the development of a novel enzymatic low‐lactose determination method termed LOLAC (low lactose), which is based on an optimized glucose removal pre‐treatment step followed by a sequential enzymatic assay that measures residual glucose and lactose in a single cuvette. Sensitivity was improved over existing enzymatic lactose assays through the extension of the typical glucose detection biochemical pathway to amplify the signal response. Selectivity for lactose in the presence of structurally similar oligosaccharides was provided by using a β-galactosidase with much improved selectivity over the analytical industry standards from Aspergillus oryzae and Escherichia coli (EcLacZ), coupled with a ‘creep’ calculation adjustment to account for any overestimation. The resulting enzymatic method was fully characterized in terms of its linear range (2.3-113 mg per 100 g), limit of detection (LOD) (0.13 mg per 100 g), limit of quantification (LOQ) (0.44 mg per 100 g) and reproducibility (≤ 3.2% coefficient of variation (CV)). A range of commercially available lactose‐free samples were analyzed with spiking experiments and excellent recoveries were obtained. Lactose quantitation in lactose‐free infant formula, a particularly challenging matrix, was carried out using the LOLAC method and the results compared favorably with those obtained from a United Kingdom Accreditation Service (UKAS) accredited laboratory employing quantitative high performance anion exchange chromatography - pulsed amperometric detection (HPAEC‐PAD) analysis. Conclusion: The LOLAC assay is the first reported enzymatic method that accurately quantitates lactose in lactose‐free samples.

The effects of desugarization using glucose oxidase/catalase and spray‐drying conditions on gelling properties of duck albumen powder were studied. Gelling temperatures increased as spray‐drying inlet temperatures (140-180°C) were increased (p  < .05). ΔE*, a*‐, and b*‐ values of gel increased but L* and whiteness decreased when higher spray‐drying temperatures were used (p  < .05). However, whiteness and lightness of albumen gel were drastically increased after desugarization (p  < .05). Texture profile analysis showed that hardness, springiness, gumminess, and chewiness of gel decreased with increasing spray‐drying temperatures. Moreover, gel of freeze‐dried desugarized albumen powder had higher hardness, springiness, gumminess, and chewiness than that of spray‐dried nondesugarized counterpart (p  < .05). Albumen gel prepared from desugarized albumen powder showed the compact network with more connectivity and smaller voids than that from nondesugarized one as visualized by scanning electron microscopy, regardless of drying conditions. Prior desugarization could lower browning and increased gelling properties of duck albumen powder. Higher spray drying inlet temperature generally exhibited the adverse effect on properties of resulting albumen powder. Both desugarization and drying conditions had the profound influence on characteristics and textural property of duck egg albumen.

Microwave (MW) thermal heating has been proposed as an efficient method for honey liquefaction, while maintaining honey quality criteria. However, little is known about the effects of MW thermal heating on honey antibacterial activity. In this study, we aimed to determine the effects of MW heating on the antibacterial activity of raw rapeseed honeys against Pseudomonas aeruginosa and Staphylococcus aureus, with a particular focus on two major bee-derived antibacterial components, defensin-1 and hydrogen peroxide (H₂O₂). Our results demonstrated that MW thermal heating completely abolished honey antibacterial activity whereas conventional thermal treatment at 45 and 55°C did not affect the antibacterial activity of honey samples. A significant decrease in both glucose oxidase activity and H2O2 production as well as defensin-1 amount was observed in MW-treated samples. Given that defensin-1 and H₂O₂ are regular antibacterial components of all honeys, MW heating may have similar negative effects on every type of crystallized/liquid honey.

Glucose oxidase (GOX) from Aspergillus niger is a well-characterised glycoprotein consisting of two identical 80-kDa subunits with two FAD co-enzymes bound. Both the DNA sequence and protein structure at 1.9 Ǻ have been determined and reported previously. GOX catalyses the oxidation of D-glucose (C₆H₁₂O₆) to D-gluconolactone (C₆H₁₀O₆) and hydrogen peroxide. GOX is produced naturally in some fungi and insects where its catalytic product, hydrogen peroxide, acts as an anti-bacterial and anti-fungal agent. GOX is Generally Regarded As Safe, and GOX from A. niger is the basis of many industrial applications. GOX-catalysed reaction removes oxygen and generates hydrogen peroxide, a trait utilised in food preservation. GOX has also been used in baking, dry egg powder production, wine production, gluconic acid production, etc. Its electrochemical activity makes it an important component in glucose sensors and potentially in fuel cell applications. This paper will give a brief background on the natural occurrence, functions as well as the properties of glucose oxidase. A good coverage on the diverse uses of glucose oxidase in the industry is presented with a brief outline on the working principles in the various settings. Furthermore, food grade GOX preparations are relatively affordable and widely available; the readers may be encouraged to explore other potential uses of GOX. One example is that GOX-catalysed reaction generates significant amount of heat (~200 kJ/mol), and this property has been mostly neglected in the various applications described so far.