Based on the theory of intermolecular forces and the Hildebrand relation, a generalized equation in terms of refractive index is proposed to estimate viscosity, thermal conductivity and diffusion coefficients of liquid non-polar compounds at various temperatures. Analytical equations are provided to estimate transport properties of n-alkanes in terms of molecular weight. Average deviations for all three properties of various hydrocarbons from Cs to CZ0 are within I % for a large number of data points. The proposed equation also predicts transport properties of some polar compounds with a reasonable degree of accuracy.

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We report our attempts to increase ethanol production from Zymomonas mobilis PTCC 1718, by optimization of the components of growth medium and culture conditions. First, low cost substrates, carbon and nitrogen sources, temperature and initial pH were optimized by one-factor-at-a-time method. Then, nutritional improvement was performed using Taguchi method. Amongst the different selected sources, sucrose and wheat bran have significant effects on ethanol production. The optimum temperature, inoculum-size and pH were 50°C, 12% (v/v) and 5.5, respectively. The optimal concentrations of nutritional components for improved ethanol production were‫׃‬ 2.5 g/L sucrose, 1.5 g/L whey, 0.25 g/L wheat bran extract, 0.5 g/L yeast extract, 0.25 g/L peptone, 0.7 g/L KH 2 PO 4 , 0.1 g/L (NH 4) 2 SO 4 and 0.05 g/L MgSO 4. Ethanol production, which was 14.49 g/L (w/v) in the basal medium, increased to 41.67 g/L (w/v) and 86.26 g/L (v/v); about 2.8 and 5.9-fold higher than that in the basal medium, after optimization with one-factor-at-a-time and Taguchi method, respectively. Bioreactor fermentation was carried out in a 15 L stirred fermentor under optimal condition. Maximum ethanol production in 15 L fermentor indicated 91.22 g/L (w/v), about 6.3 fold higher than the basal medium.

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