Effect of temperature and enzyme origin on the enzymatic synthesis of oligosaccharides.

The aim of this research is to quantify the effect of temperature and enzyme origin on the enzymatic synthesis of oligosaccharides. Quantification of these effects is important because temperature and enzyme origin are important process parameters. A kinetic model was used to describe the concentrations in time. The kinetic parameters were determined by using data obtained in batch experiments at various temperatures (20, 30, 40, and 50 degrees C) and by using beta-galactosidases from Bacillus circulans, Aspergillus oryzae, Kluyveromyces lactis, and Kluyveromyces fragilis. The effect of temperature on the kinetic parameters could be described with the Arrhenius equation, except for the inhibition parameter. Slightly higher oligosaccharide yields were found at higher temperatures. However, the influence of the initial lactose concentration was much larger. The higher yield at higher temperatures is an additional advantage when operating at high initial lactose concentrations and consequently elevated temperatures. Clear differences between the beta-galactosidases were found concerning amount, size, and type of oligosaccharides produced. The beta-galactosidase from B. circulans produced the most abundant amount, the most different, and largest-sized oligosaccharides. The beta-galactosidases from Kluyveromyces spp. produced mainly trisaccharides. The kinetic parameters for the different enzymes were determined and differences were discussed.

Modelling and parameter estimation of the enzymatic synthesis of oligosaccharides by beta-galactosidase from bacillus circulans

The aim of this research is to develop a model to describe oligosaccharide synthesis and simultaneously lactose hydrolysis. Model A (engineering approach) and model B (biochemical approach) were used to describe the data obtained in batch experiments with beta-galactosidase from Bacillus circulans at various initial lactose concentrations (from 0.19 to 0.59 mol.kg(-1)). A procedure was developed to fit the model parameters and to select the most suitable model. The procedure can also be used for other kinetically controlled reactions. Each experiment was considered as an independent estimation of the model parameters, and consequently, model parameters were fitted to each experiment separately. Estimation of the parameters per experiment preserved the time dependence of the measurements and yielded independent sets of parameters. The next step was to study by ordinary regression methods whether parameters were constant under the altering conditions examined. Throughout all experiments, the parameters of model B did not show a trend upon the initial lactose concentration when inhibition was included. Therefore model B, a galactosyl-enzyme complex-based model, was chosen to describe the oligosaccharide synthesis, and one parameter set was determined for various initial lactose concentrations. Copyright 1999 John Wiley & Sons, Inc.