[show abstract][hide abstract] ABSTRACT: The β-galactosidase from Talaromyces thermophilus CBS 236.58 immobilized onto Eupergit C produced galacto-oligosaccharides (GalOS) in batchwise and continuous packed-bed mode
of operation. A maximum yield of GalOS of 12, 39 and 80gl−1 was obtained for initial lactose concentrations of 50, 100 and 200gl−1, respectively, for batch conversion experiments. The immobilized enzyme could be re-used for several cycles for lactose hydrolysis
and transformation. The maximum GalOS concentration of approximately 50gl−1 was obtained with the dilution rate of 0.375h−1 in a packed-bed reactor, when using an initial lactose concentration of 200gl−1. Continuous conversion of lactose in the packed-bed reactor resulted in the formation of relatively more trisaccharides than
when employing the immobilized enzyme in discontinuous mode of operation.
World Journal of Microbiology and Biotechnology 01/2007; 23(6):759-764. · 1.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: Discontinuous and continuous processes of lactose hydrolysis and concomitant galacto-oligosaccharide (GalOS) formation were studied. To this end a wide experimental range of the main variables was evaluated, including the initial lactose concentration, the degree of lactose conversion, the pH value and the temperature for discontinuous transformations, while the initial lactose concentration and the feed rate were varied for the continuous process. For both processes a high-initial lactose concentration proved to be advantageous for the formation of GalOS. The maximum amount of GalOS (100 g/L, corresponding to a yield of approximately 50% based on the initially employed lactose) was obtained after 8 h of incubation when using 200 g/L lactose as substrate and 90% lactose hydrolysis was observed. GalOS productivity in the continuous process (g/L.h) was enhanced by an increase of the flow rate. The maximum GalOS productivity of 70 g/L.h was obtained at a flow rate of 24 mL/h when using a reactor with a total working volume of 21 mL. As was evident from these experiments, this beta-galactosidase from a moderately thermophilic fungus showed a strong transgalactosylation activity and can be used for the formation of GalOS, sugars that are of considerable interest for functional food applications because of their presumed healthpromoting effects.
[show abstract][hide abstract] ABSTRACT: An intracellular beta-glycoside hydrolase with beta-glucosidase and beta-galactosidase activity, designated beta-glucosidase BGL1, was isolated to apparent homogeneity from the thermophilic ascomycete Talaromyces thermophilus CBS 236.58. The monomeric enzyme has a molecular mass of 50 kDa (SDS-PAGE) and an isoelectric point of 4.5-4.6. The enzyme is active with both glucosides such as cellobiose and galactosides including lactose; based on the catalytic efficiencies determined glucosides are the preferred substrates. beta-Galactosidase activity of BGL1 is activated by various mono and divalent cations including Na+, K+ and Mg2+, and it is moderately inhibited by its reaction products glucose and galactose. Its pH optimum for the hydrolysis of galactosides is in the range of 5.5-6.0, and its optimum temperature was found to be 50 degrees C (15 min assay). In addition to its hydrolytic activity, BGL1 shows a significant transferase activity which results in the formation of galacto-oligosaccharides. These have recently attracted interest because of possible applications in food industry. The highest yields of oligosaccharides was approximately 20% when using 38 gl(-1) lactose as the starting material.
Journal of Biotechnology 06/2006; 123(3):304-13. · 3.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: beta-Galactosidase from the fungus Talaromyces thermophilus CBS 236.58 was immobilized by covalent attachment onto the insoluble carrier Eupergit C with a high binding efficiency of 95%. Immobilization increased both activity and stability at higher pH values and temperature when compared with the free enzyme. Especially the effect of immobilization on thermostability is notable. This is expressed by the half-lifetime of the activity at 50 degrees C, which was determined to be 8 and 27 h for the free and immobilized enzymes, respectively. Although immobilization did not significantly change kinetic parameters for the substrate lactose, a considerable decrease in the maximum reaction velocity V(max) was observed for the artificial substrate o-nitrophenyl-beta-D-galactopyranoside (oNPG). The hydrolysis of both oNPG and lactose is competitively inhibited by the end products glucose and galactose. However, this inhibition is only very moderate as judged from kinetic analysis with glucose exerting a more pronounced inhibitory effect. It was evident from bioconversion experiments with 20% lactose as substrate, that the immobilized enzyme showed a strong transgalactosylation reaction, resulting in the formation of galactooligosaccharides (GalOS). The maximum yield of GalOS of 34% was obtained when the degree of lactose conversion was roughly 80%. Hence, this immobilized enzyme can be useful both for the cleavage of lactose at elevated temperatures, and the formation of GalOS, prebiotic sugars that have a number of interesting properties for food applications.
Applied Biochemistry and Biotechnology 02/2006; 129-132:215-25. · 1.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: Beta-Galactosidase is enzyme that hydrolyses of lactose to glucose and galactose. The present study focused on characterization of beta-galactosidase from thermophilic microoganism isolated from Pong Dueat hot spring, Chaingmai Province, Thailand. o-Nitrophenyl-L-D-galactopyranoside (oNPG) was used as a substrate to determine beta-galactosidase activity from strain PD1, which was found to be the active strain producing highest beta-galactosidase activity. The optimum pH and temperature for enzyme activity were 6.5 and 55 deg C, respectively. The enzyme was stable at pH ranges of 6 to 10. The half-life of enzyme at 80, 70, 60, 55, 50 and 45 deg C were 0.5, 2, 31, 62, 87 and 435 h, respectively. The K sub(m) and V sub(max) values for the synthetic substrates oNPG were 11 mM and 1.1*10**(-2) mmol/L/min. Summaries (En, Th) 4 ill.