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Abstract:The kinetic behavior of soluble and insoluble forms of dextransucrase from Leuconostoc mesenteroides NRRL B-1299 was investigated with sucrose as substrate and maltose as acceptor. To study the parameters involved, a kinetic model was applied that was previously developed for L. mesenteroides NRRL B-512F dextransucrase. There are significant correlations between the parameters of the soluble form of B-1299 dextransucrase and those calculated for the B-512F enzyme; that is, their properties are comparable and differ from those of the insoluble form of B-1299 dextransucrase. Whereas the calculated parameters for high maltose concentrations describe the kinetic behavior very well, the time curves for low maltose concentrations were not described correctly. Therefore, the parameters were calculated separately for the two ranges.

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Dextransucrase catalyses the formation of dextran, but also of numerous oligosaccharides from sucrose and different acceptors, if appropriate conditions are chosen. Much experimental work has been carried out and a scheme of reactions and a mathematical model have been developed to describe the complex kinetic behaviour of the enzyme. A computer program was used to calculate the parameters of the model from a broad range of experimental data, investigating a large number of kinetic tests with the acceptors maltose and fructose. The results lead to design considerations for a continuous reactor system with immobilized dextransucrase to produce leucrose, a disaccharide of industrial interest. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 583–592, 1999.

This work focuses on the implementation of high performance systems to the wastewater treatment of sugar factories. For this purpose, systems with immobilised bacteria were studied. For the hydrolysis of organic matter and denitrification, fluidized bed reactors were used. The nitrification was studied with an airlift reactor system. Both hydrolysis and nitrogen elimination were investigated on laboratory and pilot scales in sugar factories. Although with porous materials higher biomass concentrations are attainable for the hydrolysis (up to 55 kg/m3), for economical reasons sand was used (22.5 kg/m3) for the pilot scale-study. With a pilot-scale reactor (volume 1 m3) the maximum sucrose conversion rate achieved with sand in the first campaign was 52 kg/(m3 d). For the nitrogen elimination on the pilot scale, a system with denitrification and nitrification was combined. The highest performance for the nitrification (reactor volume: 0.68 m3) with pumice as support material was 1.2 kg NH4-N/(m3 d), limiting the whole system. The denitrification rate (reactor volume: 0.12 m3) was four times higher (3.5-5 kg NO3-N/(m3 d). Rules of the modelling of the system are discussed.