Study on CTP production from CMP by beer yeast cell immobilized in PVA / 生物工程学报

With PVA as the carrier, the frozen beer yeast cells were immobilized for production of CTP from CMP. we explored the optimal condition of the immobilization from the aspects of the type, concentration of the PVA, and the immobilizing methods of cells In all 8 continuous batch of fermentation under the reactional condition of the immobilized cells, the conversion rate of CTP were maintained about 85% - 95%. Moreever, the storage stability of immobilized cells were investigated, and the products was also isolated and identifided by HPLC.

Cloning of human uracil N-glycosylase and its detection in cancer tissues by quantitative RT-PCR / 生物工程学报

The uracil in DNA comes from either the misincorporation of dUTP in place of dTTP or deamination of cytosine. In the latter case, it can result in a GC to AT transition mutation if the uracil is not removed before DNA replication. Base excision repair (BER) is a major pathway for removing DNA lesions arising from endogenous processes as well as those induced by exposure to exogenous chemicals or irradiation. BER is initiated by DNA glycosylases that excise aberrant bases from DNA by cleavage of the N-glycosidic bond linking to the base of its deoxyribose sugar. Uracil N-glycosylase (UNG) is the enzyme responsible for the first step in the BER pathway that specifically removes uracil from DNA. The UNG gene undergoes both temporal and spatial regulation mainly at the level of transcription. Normally cancer cells undergo over-proliferation and up-regulate their UNG during tumorigenesis. In this study we examine the correlation between UNG level and carcinogenesis, and explore the possibility of using UNG as a marker for cancer diagnosis. Human UNG gene was amplified from the total RNA of the human choriocarcinoma cell line, JEG-3, by RT-PCR. After purification, the 942bp full-length UNG cDNA coding sequence was digested with EcoR I and Sal I, and cloned into the digested pET-21 to construct a recombinant vector, pUNG. The UNG protein was expressed under the control of T7 promoter in E. coli BL21 (DE3) cells induced with IPTG. After ultrasonic treatment, the cell lysate and precipitate were analyzed by SDS-PAGE and a 39kD band was detected. The plasmid was serially diluted at appropriate concentrations and employed as standards in the subsequent quantification. Total RNAs were extracted from 18 pairs of clinical samples, each pair contains a sample of esophageal squamous cell carcinoma (ESCC) tissue and its surrounding normal esophageal epithelia. The copy numbers of UNG mRNA in these RNA samples were determined by real-time quantitative RT-PCR using a Lightcycler (Roche). UNG was present in 13 cases of ESCC (13/18, n = 18) but absent in all of the normal tissues. The results indicated that there was a correlation between high level of UNG expression and the carcinogenesis of ESCC.

Characterization and Identification of a Biphenyl Degrading Strain / 微生物学通报

R04, a Gram-positive bacterium, which can use biphenyl as the sole carbon source, was isolated from soil contaminated with oil in northern China. The bacterium has high biphenyl degradation efficiency and also can degrade polychlorinated biphenyl congeners, Aroclor1221 and Aroclor 1242. The bacterium was identified as Rhodococcus pyridinovorans by the method of 16S rDNA gene sequencing (accession No. AY072745).

METHODS OF THE DIRECTED MOLECULAR EVOLUTION OF ENZYNE IN VITRO / 微生物学通报

The directed molecular evolution of enzyme in vitro can not only improve the efficiency of evolution, but also evolve enzyme according to the investigator's desire. This review summed up the feasible methods of this novel technique.