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A dynamic mathematical model for liquid-phase polymerization in loop reactors was de®eloped and implemented in language C using S-functions in a MATLABrSIMU

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We studied the utilization of protein-hydrolyzed sweet cheese whey as a medium for the production of beta-galactosidase by the yeasts Kluyveromyces marxianus CBS 712 and CBS 6556. The conditions for growth were determined in shake cultures. The best growth occurred at pH 5.5 and 37 degrees C. Strain CBS 6556 grew in cheese whey in natura, while strain CBS 712 needed cheese whey supplemented with yeast extract. Each yeast was grown in a bioreactor under these conditions. The strains produced equivalent amounts of beta-galactosidase. To optimize the process, strain CBS 6556 was grown in concentrated cheese whey, resulting in a higher beta-galactosidase production. The beta-galactosidase produced by strain CBS 6556 produced maximum activity at 37 degrees C, and had low stability at room temperature (30 degrees C) as well as at a storage temperature of 4 degrees C. At -4 degrees C and -18 degrees C, the enzyme maintained its activity for over 9 weeks.

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Catalytic dehydration of ethanol is a key step in the production of polyethylene from renewable raw materials. Obtaining a mathematical model to optimize the ethanol-to-ethylene reactor setup is of great interest to the industry, allowing the optimal design of larger plants and improvements to existing plants. This work presents a phenomenological model of an ethanol dehydration reactor that takes into account 8 chemical reactions and 10 chemical species, considering nonidealities in the reaction rates and axial catalyst activity profile. Additionally, the axial variation of pressure, velocity, and thermodynamics properties are considered in the proposed model. Model validation at different operating conditions shows that the predicted temperature and composition profiles match the data from an industrial plant with relative deviations below 5% and from a pilot plant with relative deviation below 0.4%.

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