Sulphydryl oxidase: Properties and applications

Activation of Inert Supports for Enzyme(s) Immobilization Harnessing Biocatalytic Sustainability for Perennial Utilization

Although Nature's evolution and intelligence have gifted humankind with noteworthy enzyme candidates to simplify complex reactions with ultrafast, overselective, effortless, mild biological reactions for millions of years, their availability at minute-scale, short-range time-temperature stability, and purification costs hardly justify recycling/or reuse. Covalent immobilization, particularly via multipoint bonds, prevents denaturing, maintains activities for long-range time, pH, and temperature, and makes catalysts available for repetitive usages; which attracts researchers and industries to bring more immobilized enzyme contenders in science and commercial progressions. Inert-support activation, the most crucial step, needs appropriate activators; under mild conditions, the activator's functional group(s) still present on the activated support rapidly couples the enzyme, preventing unfolding and keeping the active site alive. This review summarizes exciting experimental advances, from the 1950s until today, in the activation strategies of various inert supports with five different surface activators, the cyanogen bromide, the isocyanate/isothiocyanate, the glutaraldehyde, the carbodiimide (with or without N-hydroxysuccinimide (NHS)), and the diazo group, for the immobilization of diverse enzymes for broader applications. These activators under mild pH (7.5 ± 0.5) and temperature (27 ± 3 °C) and ordinary stirring witnessed support activation and enzyme coupling and put off unfolding, harnessing addressable activities (CNBr: 40 ± 10%; -N═C═O/-N═C═S: 32 ± 7%; GA: 70 ± 15%; CDI: 60 ± 10%; -N+≡N: 80 ± 15%), while underprivileged stability, longevity, and reusabilities keep future investigations alive.

Discovery of novel secreted fungal sulfhydryl oxidases with a plate test screen

Sulfhydryl oxidases (SOX) are FAD-dependent enzymes capable of oxidising free thiol groups and forming disulphide bonds. Although the quantity of scientific papers and suggested applications for SOX is constantly increasing, only a limited number of microbial SOX have been reported and are commercially available. Hence, the aim of this study was to develop a fast and reliable qualitative plate test for screening novel secreted fungal SOX. The screening was based on the Ellman's reagent, i.e. 5,5'-dithiobis[2-nitrobenzoic acid]. Altogether, 32 fungal strains from an in-house culture collection were screened. A total of 13 SOX-producing strains were found positive in the plate test screen. The novel SOX producers were Aspergillus tubingensis, Chaetomium globusum, Melanocarpus albomyces, Penicillium aurantiogriseum, Penicillium funiculosum, Coniophora puteana and Trametes hirsuta. Six of the discovered SOX were partially characterised by determination of isoelectric point, pH optimum and substrate specificity. A. tubingensis was identified as the most efficient novel SOX producer.

Effect of Various Dairy Packaging Materials on the Shelf Life and Flavor of Pasteurized Milk

Milk from three different dairies (each a separate trial: 1, 2, and 3) was standardized to 2% fat and pasteurized at 92.2, 84.0, and 76.4 degrees C (temperatures 1, 2, and 3, respectively) for 25 s and packaged into six different packaging boards, [standard (A) milk boards with standard seam; juice boards with standard (B) and J-bottom (D) seams; barrier boards with standard (C) and J-bottom (E) seams; and foil (F) boards with J-bottom seam], resulting in 18 different treatments. Standard plate count (SPC) was used to test for microbial quality, and taste a panel was employed for flavor acceptability and difference on the milk stored at 6.7 degrees C at 1, 2, 3, and 4 wk. Statistical analysis of taste panel data showed that the flavor of milk samples A2, B2, and D2 deteriorated faster than the blind control (freshly high temperature, short time pasteurized low fat milk processed at 80.6 degrees C for 25 s). The flavor of milk packaged in standard (A) and juice (B and D) boards deteriorated at a faster rate than milk packaged in barrier (C and E) and foil (F) boards. Microbial counts showed that milk samples stored at 6.7 degrees C in trials 2 and 3 produced high SPC at wk 3 (ranges of bacteria in cfu/ml for trial 2: 9.9 x 10(1)-1.8 x 10(6) and trial 3: 2.5 x 10(5)-5.5 x 10(8)). In trial 1, high SPC began at wk 4 (9.9 x 10(1)-5.5 x 10(5) cfu/ml). Milk processed at 76.4 degrees C had the lowest bacterial growth rate, and milk processed at 84.0 degrees C had the highest bacterial growth rate. Different boards had no effects (P > 0.05) on the bacterial growth rates. It appeared that the lower the SPC of the raw milk, the slower the bacterial growth rate after 2 wk of storage. Milk samples stored at 1.7 degrees C maintained low SPC at wk 4, with counts of 0 to 40 cfu/ml for trial 2 and 0 to 200 cfu/ml for trial 3.