关键词: 扩张青霉；鉴定；β-半乳糖苷酶；转糖基；低聚半乳糖

Abstract:

Strain F3 was isolated from soil and produced transglycosyl βgalactosidase. It was identified as Penicillum expansum F3 by means of morphological characteristics and 18S rDNA sequence analysis. Medium and fermentation conditions for its βgalactosidase production were optimized by single factor and orthogonal experiments. The final yield of the enzyme reached 2?245.2?U/L in the medium composed of 2% glucose，1% yeast extract, 1.5% peptone and 0.3% NaCl at initial pH 6.0 and 28?℃ for 40?h, which increased threefold compare to before optimization. The effects of pH, temperature and time on galactooligosaccharides (GOS) synthesis were investigated. A purity of 30.6% (w/w) GOS was obtained from 30% lactose solution at pH 4.5 and 50?℃ for 24?h. Transgalactosyl trisaccharides were the main products, accounting for more than 80% of the GOS product.

Key words:  Penicillium expansum;Identification;β-galactosidase, galactosylation;galactooligosaccharide