Galactosidase had applied in food and feed industries for hydrolyzing raYnose series oligosaccharides (RO) that are the factors primarily responsible for Xatulence upon ingestion of soybean-derived products. The objective of the current work was to purify the -galactosidase of Aspergillus foetidus ZU-G1 and compared the biochemical and hydrolytic properties of three major -galactosidase forms ( -gal I, -gal II and -gal III). The molecular mass of the puriWed enzyme as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was 106.3, 49.7 and 109.9 kDa, respectively. Its optimum reaction temperature was 60°C and stable below 50°C. The optimum pH of -gal I and -gal III was 5.0 and -gal II was 4.0. Under 28°C conditions for 24 h, -gal I was stable at pH 4.0, -gal II was stable at pH 6.0, and -gal III was pH 5.0. -Galactosidase was completely inhibited by Ag + . CuSO 4 ·5H 2 O and SDS were powerful inhibitors of -gal I and -gal III but had little eVect to -gal II. EDTA did not strongly aVect -gal I and -gal III, while strongly aVect -gal II. CaCl 2 ·2H 2 O, MgSO 4 ·7H 2 O and MnSO 4 ·7H 2 O were activation for -gal I, -gal II and -gal III. No signiWcant inhibition of enzymes activity was observed in the presence of raYnose, lactose as well as other sugars tested. Synthetic substrate p-nitrophenyl--D-galactopyranoside was not preferentially hydrolyzed than natural substrates, such as melibiose, stachyose and raYnose. Under 40 and 50°C incubation for 1-5 h, the stachyose of soybean milk was degraded by -gal I, -gal II and -gal III and strongly hydrolyzed by -gal II, and the raYnose of soybean milk was completely hydrolyzed by -gal II and weakly hydrolyzed by -gal I and -gal III. The distinct hydrolytic and biochemical properties of -gal I, -gal II and -gal III further signify the -galactosidase of A. foetidus ZU-G1 was propitious to soybean milk and related food industry.

A 3.6-kb plasmid, designated pND324, was isolated from Lactococcus lactis subsp. lactis LL57-1. Sequence analysis revealed the presence of three open reading frames, rep324, orfX1 and orfX2, which are flanked by two non-coding regions, ori324 and cisE. The minimal replication region of pND324 consists of ori324 and rep324, which is closely related to the lactococcal theta-type replicons of the pWV02/pCI305 family. pND324 was stable at both 30 degrees C and 37 degrees C, whereas derivatives that lack cisE were highly unstable at 37 degrees C, indicating that cisE is essential for thermostability. Sequences that are similar to orfX1 are commonly present in the lactococcal theta-type plasmids. The orfX2 product is homologous to TrfA, a 43-kDa protein of the E. coli theta-type plasmid RK2 required for replication and maintenance. Plasmid deletion and stability analyses showed that orfX2 is involved in the thermostability of pND324. Based on the minimal replication region of pND324, an integrative cloning vector, designated pND421, was constructed. In L. lactis LM0230, cells that carried pND421 integrated into its host chromosomal DNA could be recovered readily following incubation at 37 degrees C for 40 generations. The integrated plasmid was totally stable for at least 100 generations without selection at 30 degrees C.