To develop an effective fermentation system for producing Escherichia coliphytase AppA2, we expressed the enzyme in three inducible yeast systems: Saccharomyces cerevisiae (pYES2), Schizosaccharomyces pombe (pDS472a), and Pichia pastoris (pPICZ alphaA), and one constitutive system: P. pastoris (pGAPZalphaA). All four systems produced an extracellular functional AppA2 phytase with apparent molecular masses ranging from 51.5 to 56 kDa. During 8-day batch fermentation in shaking flasks, the inducible Pichia system produced the highest activity (272 units ml(-1) medium), whereas the Schizo. pombe system produced the lowest activity (2.8 units ml(-1)). The AppA2 phytase expressed in Schizo. pombe had 60-75% lower K(m)for sodium phytate and 28% higher heat-stability at 65 degrees C than that expressed in other three systems. However, all four recombinant AppA2 phytases had pH optimum at 3.5 and temperature optimum at 55 degrees C and similar efficacy in hydrolyzing phytate-phosphate from soybean meal.
A tremendous amount of plastic and tire waste is generated every day. Pyrolysis gives a sustainable plastic and tire waste management solution by transforming them into high-value carbonaceous materials (i.e., char). Char made from plastic or tire waste can be used as a modifier for asphalt binder (i.e., bitumen), in order to improve the properties and performance of base bitumen. In most cases, the char is produced from waste feedstock at ≤300°C, most likely due to the high volatile matter content in feedstock. These chars have been proven experimentally to enhance the deformation resistance, rutting resistance, stiffness, and elasticity of bitumen. The optimal dosage of char in the modification process is highly associated with the kind of waste feedstock and pyrolysis conditions under which the char is made. The present review highlights the promise of the char materials derived from plastic and tire waste for use in materials applied to civil and construction industries, which is aimed specifically at expanding the application of chars made from plastic and tire waste beyond their typical applications, such as in environmental remediation and catalysts.
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