Production of tyrosinase by Auricularia auricula using low cost fermentation medium
Low cost fermentation media using agricultural by-products (wheat bran extract, rice bran extract and soybean meal extract) as a major nutrient source, were evaluated for the production of tyrosinase from the fungus Auricularia auricula in submerged culture. In single-factor experiments, three components (wheat bran extract, casein and CuSO4) were chosen to further optimize medium composition using response surface methodology (RSM). The central composite experimental results showed the following optimum medium composition: wheat bran extract 36.0 %, casein 1.1 g/l and CuSO4 0.13 g/l. Under these conditions, the highest tyrosinase activity was 17.22 U/ml, which was 2.1 fold higher than that obtained using the non-optimized medium. The present study is the first to report the statistical optimization of medium composition for production of tyrosinase by A. auricula using cheaper wheat bran extract as a major nutrient source. These results might provide a reference for the development of a cost-effective medium for commercial production of tyrosinase.
Optimization of Bacillus licheniformis MAL tyrosinase: in vitro anticancer activity for brown and black eumelanin
The influence of tyrosinase in catalyzes/stimulates the eumelanin production was studied. Accordingly, bacterial sp. was isolated and identified as Bacillus licheniformis based on 16S rRNA. It could grow and gave monophenolase and diphenolase productivity in medium contained tyrosin and Cu2+ only. The tyrosinase enzymes were optimized by studying different environmental and nutritional factors. The maximum monophenolase and diphenolase productivity were obtained at 60 °C, pH9, Cu2+(0.01g), liver extract (1 g/L) and the oxygen level fixed at 20%. Also, the mannose as a carbon source increased the monophenolase production 6.2 times. For the first time, two types of eumelanin were extracted by hydrochloric acid treatment. The black and brown eumelanin weighed (0.1 g/100 mL and 0.7 g/100 mL respectively) and characterized by using FTIR and UV/Vis spectroscopy techniques. Their morphological structure and its elemental composition were characterized by SEM and EDAX respectively. The black melanin showed promising anticancer activity towards HEPG-2 and HCT-116 cell lines with IC50 values (6.15, 5.54 μg) compared to Doxorubicin (4.05, 4.45 μg) respectively.
Phase characterisation of simulated high burn-up UO2 fuel
Abstract To determine the lattice constant variation with burn-up and the oxidation behaviour at high temperatures, simulated UO2-spent fuels with burn-ups up to 200 GWd tM−1 were prepared by cold pressing and sintering and characterised by X-ray diffraction analysis and thermogravimetry. The fcc-lattice parameter of the sintered samples determined at room temperature, showed a continuous decrease with the simulated burn-up. During oxidation the conversion of the simulated fuels to the (U,FP)4O9 and (U,FP)3O8-type phases was strongly delayed when the simulated burn-up exceeded 80 GWd tM−1. Also, at high burn-ups (>100 GWd tM−1), large fractions of the (U,FP)4O9-type phase remained untransformed to (U,FP)3O8 after prolonged exposure to air at 950–1000°C. This suggests a marked widening of the (U,FP)4O9-phase field when the amount of substituted uranium atoms exceeds values of about 8%.