Construction and Expression of β-galactosidase Genetically Engineered Lactococcus lactis

Our objective is to solve the lactose malabsorption and intolerance of human beings by combining micro-ecology path with genetic engineering technique. Plasmid pMG36e was used to clone and express a β-galactosidase gene from L. delbrueckü bulgaricus strain 1.1480 in the Lactococcus lactis subsp. cremoris MG1363 and Lactococcus lactis subsp. lactis IL1403. The recombinant plasmid was preserved and proliferated in Escherichia coli ( E. coli) JM109, and transformed into MG1363 and IL1403 by electroporation. The protein expression was studied. ( 1 ) The bifidobacterium culture medium ( BBL) was suitable for the growth of the strain 1.1480. (2) With 13 amino acids at the N-terminus from the vector, β-gal- actosidase fusion protein (which retained the enzyme activity) could be successfully expressed in E. coli JM109, MG1363 and IL1403, but the expression quantity was larger in the former than in the latter two. (3) The SD sequence designed could be successfully recognized by both the E. coli and the Lactococcus lactis, but the expression level of the non-fusion β-galac- tosidase protein was lower than that of the fusion protein in the same host. The β-galactosidase genetically engineered E. coli JM109 is a useful tool to produce this enzyme in vitro . The signal peptide of the usp45 protein from the Lactococcus lac- tis can be added before the promoter sequence to promote β-galactosidase secretion from Lactococcus lactis . The potential ap- plication of the β-galactosidase genetically engineered MG1363 and IL1403 to cure the lactose malabsorption and lactose in- tolerance in both health food and medicine is promising.

Immobilization biological activated carbon used in advanced drinking water treatment

Bacteria separated from a mature filter bed of groundwater treatment plants were incubated in a culture media containing iron and manganese. A consortium of 5 strains of bacteria removing iron and manganese were obtained by repeated enrichment culturing. It was shown from the experiments of effect factors that iron-manganese removal bacteria in the culture media containing both Fe and Mn grew better than in that containing only Fe, however, they were unable to grow in the culture media containing only Mn. When comparing the bacteria biomass in the case of ρ (DO)=2.8 mg/L and ρ (DO)=9.0 mg/L, no significant difference was found. The engineering bacteria removing the organic and the bacteria removing iron and manganese were simultaneously inoculated into activated carbon reactor to treat the effluent of distribution network. The experimental results showed that by using IBAC (Immobilization Biological Activated Carbon) treatment, the removal efficiency of iron, manganese and permanganate index was more than 98%, 96% and 55%, respectively. After the influent with turbidity of 1.5 NTU, color of 25 degree and offensive odor was treated, the turbidity and color of effluence were less than 0.5 NTU and 15 degree, respectively, and it was odorless. It is determined that the cooperation function of engineering bacteria and activated carbon achieved advanced drinking water treatment.

PARALLEL DYNAMIC ITERATION METHODS FOR SOLVING NONLINEAR TIME-PERIODIC DIFFERENTIAL-ALGEBRAIC EQUATIONS

In this paper we presented a convergence condition of parallel dynamic iteration methods for a nonlinear system of differential-algebraic equations with a periodic constraint. The convergence criterion is decided by the spectral expression of a linear operator derived from system partitions. Numerical experiments given here confirm the theoretical work of the paper.