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A quick and simple method, based on elemental and moisture analyses, is proposed for estimating the mean molecular weight of alkylpolyglucosides and fatty alcohol ethoxylates, which are nonionic surfactants that are attracting growing interest for their ease of biodegradation. Analyses for the water content and the elemental composition were carried out for three alkylpolyglucosides (Henkel-Cognis): Glucopon 215, Glucopon 600, and Glucopon 650, as well as for five fattyalcohol ethoxylates (Kao Corporation): FINDET 10/15, FINDET 10/18, FINDET 1214N/16, FINDET 1214N/23, and FINDET 1618/A18. Application of the method requires knowing the mean number of carbons in the fatty acid chains of the surfactant. This number, in the case of the alkylpolyglucosides assayed here, has been determined experimentally by high-performance liquid chromatography.

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The enzymatic hydrolysis of soluble starch with an alpha-amylase from Bacillus licheniformis (commercial enzyme Termamyl 300 L Type DX) have been experimentally studied at pH 7.5, within the temperature range of 37-75 degrees C, at initial substrate concentrations of between 0.25 and 2.00 g/L, and enzyme concentrations of between 0.575 x 10(-4) and 13.8 x 10(-4) g/L. To follow the reaction a procedure based on the iodometric method for measuring alpha-amylase activity was used. The kinetics of the enzymatic hydrolysis was fitted to the Michaelis-Menten equation using the integral method, taking into account that the thermal deactivation of the enzyme follows a second-order kinetic. These parameters were fitted to the Arrhenius equation obtaining activation energies of 24.4 and 41.7 kJ/mol and preexponential factors of 734.9 g/L and 1.74 x 10(8) min(-1) for K(M) and k, respectively.