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Summary: Bioactive peptides generated from food proteins have gained much interest as functional foods. Recently, the application of lactic acid fermentation has developed rapidly thanks to the discovery of probiotic functions in lactic acid bacteria (LAB). Aside from converting a fermentable carbohydrate into lactic acid, many strains of LAB were found to possess proteolytic activity, which is essential for many fermentation processes. The protease enzymes produced from the proteolytic fermentation breakdown proteins in food and generate a variety of high‐value products which are discussed in this review. These substances give rise to the production of functional food that exerts diverse health benefits including antioxidant, antihypertension, antihyperglycaemic, antiinflammation, antimicrobial, and anticancer effects. The effects of proteolytic fermentation on the physicochemical and functional properties, biological activities, and sensory attributes of foods are elaborated in this review article. The application of proteolytic fermentation in various food industries, mainly the dairy industry, meat industry, bakery industry, and brewing industry, improved the technological, nutritional, biological, and sensory characteristics, as well as increased the shelf life of food. Ultimately, this review summarises in‐depth knowledge of proteolytic fermentation by LAB and generates additional interest in the development of novel proteolytically fermented products. [ABSTRACT FROM AUTHOR]

Pyranose dehydrogenase (PDH) is a quinone‐dependent extracellular flavoglycoprotein mainly produced by litter‐decomposing fungi and contributes to the degradation of lignocellulose. PDH in terms of structure and catalytic features pertains to the glucose methanol‐choline oxidoreductase family and oxidizes a wide substrate range of aldopyranoses including hexoses, pentoses, disaccharides and oligosaccharides with a high degree of regioselectivity. The purpose of this study was to rationalize the preference of PDH immobilized on an electrode with the structural features of various substrates and thus the kinetic constants were measured for various sugars. PDH was co‐immobilized on the electrode with an osmium redox polymer. Response currents for different sugars were measured using flow injection amperometry at +0.3 V vs. Ag|AgCl, KCl (0.1 M). The Michaelis‐Menten constants, the turnover numbers and the catalytic efficiency were calculated and revealed that type, orientation and configuration of the substituent play a major role on substrate preference. An OH‐group at C‐1 and C‐6 are not essential and substrate specificities are little affected by the substitution at C‐1. The presence and orientation of OH− at C‐2 and C‐3 are relevant for reactivity. Orientation of OH− at the C‐4 position has little effect, and sugars with a substitution below the plane at C‐5 are not suitable as substrate. Highest activity for oxidation of glucose, mannose and sucrose was detected at pH 8.5. Substrate Preference Pattern: the kinetic constants are used to rationalize the preference of AmPDH with the structural features of various substrates. All substrates have a hydroxyl group below and above the plane of the ring at C‐2 and C‐3, respectively and there is a preference for a hydroxyl group at C‐4 without a certain superiority in orientation. Sugars with substitutions below the plane of the ring at C‐5 do not show activity and a free hydroxyl group at C‐1 and C‐6 is not required. [ABSTRACT FROM AUTHOR]

Enzymatic fuel cells (EFCs) utilize enzymatic catalysts to convert chemical energy to electrical energy, typically by performing a 2e- oxidation of saccharides. In the case of sugars, a single 2e- oxidation does not fully exploit this energy-dense fuel that is capable of producing 24e- from its complete oxidation to CO2. Here, we propose an efficient approach to design a versatile EFC that can produce electrical energy from 12 (oligo)saccharides by combining two enzymes that possess diverse substrate specificities: pyranose dehydrogenase (PDH) and a broad glucose oxidase (bGOx). Additionally, PDH is able to perform single or two sequential oxidations of glucose (at C2 and/or C3) yielding up to 4e-, whereas bGOx only performs a single 2e- oxidation at the anomeric (C1) position. By combining PDH and bGOx, we demonstrate the ability to achieve deep oxidation of glucose and xylose, whereby each is able to undergo sequential oxidations by PDH and bGOx. Additionally, we demonstrate that this deep oxidation can yield improved performances of EFCs. For example, an EFC comprised of a bi-enzymatic PDH/bGOx bioanode using xylose as a fuel yields a maximum current density of 586 ± 3 µAcm-2 whereas mono-enzymatic PDH or bGOx EFC bioanodes result in current densities of 440 ± 4 µAcm-2 and 120 ± 1 µAcm-2, respectively. [ABSTRACT FROM AUTHOR]