Journal
APPLIED MICROBIOLOGY AND BIOTECHNOLOGY
Volume 88, Issue 1, Pages 155-165Publisher
SPRINGER
DOI: 10.1007/s00253-010-2744-7
Keywords
beta-galactosidase; Cold-adapted activity; Gene cloning; Enzyme characterization; Metagenome
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Funding
- National High Technology Research and Development Program of China (863 Program) [2007AA10Z308]
- National Natural Science Foundation of China [30970107]
- Science and Technology Plan Project of Guangdong province [2007A010900001]
- Sun Yat-sen University [2007-33000-1132628]
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A novel beta-galactosidase gene, zd410, was isolated by screening a soil metagenomic library. Sequence analysis revealed that zd410 encodes a protein of 672 amino acids with a predicted molecular weight of 78.6 kDa. The recombinant ZD410 was expressed and purified in Pichia pastoris, with a yield of ca. 300 mg from 1 L culture. The purified enzyme displayed optimal activity at 38 degrees C and pH 7.0. Given that the enzyme had 54% of the maximal activity at 20 degrees C and 11% of the maximal activity at close to 0 degrees C, ZD410 was regarded as a cold-adapted beta-galactosidase. ZD410 displays high enzymatic activity for its synthetic substrate-ONPG (o-nitrophenyl-beta-D-galactopyranoside, 243 U/mg) and its natural substrate-lactose (25.4 U/mg), while its activity was slightly stimulated by addition of Na+, K+, or Ca2+ at low concentrations. ZD410 is a good candidate of beta-galactosidases for food industry after further study.
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