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.
Statistical optimization of chitosanase production by Aspergillus sp. QD-2 in submerged fermentation
Cultivation of chitosanase production by Aspergillus sp. QD-2 under submerged fermentation was optimized. Factors including (NH4)2SO4, inoculum size and initial pH were identified by two-level Plackett-Burman design (PBD) as significant for chitosanase production. The path of steepest ascent was undertaken to determine the optimal region of three significant factors. To determine the optimal values of the significant variables, Box-Behnken design (BBD) and response surface analysis were employed. The quadratic regression model of producing chitosanase showed that the optimal cultivation conditions ((NH4)2SO4 5.164 g/l, inoculum size 8.204% (v/v) and initial pH 4.074) resulted in the improvement of chitosanase activity (85.816 U/ml) as compared to the initial level (26.515 U/ml) after 72 h of fermentation. The optimal pH and temperature of the crude chitosanase were determined to be 5.6 and 55°C, respectively.
A model for predicting heat transfer through gypsum‐board/wood‐stud walls exposed to fire
To facilitate the development of cost-effective and flexible design options there is a need to develop models to predict the fire resistance of wood-frame building assemblies. Such assemblies often derive much of their fire resistance from a protective membrane composed of gypsum board. A simple two-dimensional computer model is presented to predict heat transfer through gypsum-board/wood-stud walls exposed to fire. Input data for the thermophysical properties of gypsum board were measured exploying standard bench-scale tests. Input data for wood were selected from the literature. Small-and full-scale fire resistance tests were conducted on gypsum-board/wood-stud wall assemblies to provide data for the validation of the model. The model is shown to predict heat transfer through these walls rather well.