ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract. We purified an extracellular thermostable β-galactosidase of Saccharopolyspora rectivirgula strain V2-2, a thermophilic actinomycete, to homogeneity and characterized it to be a monomeric enzyme with a relative molecular mass of 145 000 and s° 20,w of 7.1 s. In addition to the hydrolytic activity of 1-O-substituted β-d-galactopyranosides such as lactose [a Michaelis constant K m=0.75 mm and molecular activity (k cat)=63.1 s−1 at pH 7.2 and 55° C] and p-nitrophenyl β-d-galactopyranoside (K m=0.04 mm and k cat=55.8 s−1), the enzyme had a high transgalactosylation activity. The enzyme reacted with 1.75 m lactose at 70° C and pH 7.0 for 22 h to yield oligosaccharides in a maximum yield (other than lactose) of 41% (w/w). A general structure for the major transgalactosylic products could be expressed as (Gal)n-Glc, where n is 1, 2, 3, and 4 with a glucose at a reducing terminal. These oligosaccharides could selectively promote the growth of the genus Bifidobacterium found in human intestines. S. rectivirgula β-galactosidase was stable at pH 7.2 up to 60° C (for 4 h in the presence of 10 μm MnCl2) or 70° C (for 22 h in the presence of 1.75 m lactose and 10 μm MnCl2). Thus the enzyme is applicable to an immobilized enzyme system at high temperatures (60° C〈) for efficient production of the oligosaccharides from lactose.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002530050046
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