An expression T-vector and its application at low temperatures / 生物工程学报

In modern biology and biotechnology research, recombinant gene expression has been the most popular method to obtain the target protein. In recent years, many foreign genes have been efficiently expressed in Escherichia coli. However, proteins encoded by animal, plant or mesophilic microbial genes often lose activities or become denatured within a few hours at regular growth temperatures for E. coli; some other target proteins are toxic to host cells and therefore difficult to be over-expressed. The new T-vector, pEXC-T, was constructed by combining TA cloning and cold-shock induction to obtain high expression levels with low costs. This paper reports the construction of pEXC-T and optimization of induction techniques for gene expression. Two instable proteins were tested and successfully expressed in soluble form by using pEXC vector. The development of pEXC-T offers a convenient technique for the preparations of recombinant proteins to be used in structure/function studies, or as diagnostic markers and medicinal proteins.

Expression, purification and characterization of a thermostable lactate dehydrogenase from Thermotoga maritima / 生物工程学报

The gene encoding thermostable lactate dehydrogenase (Tm-LDH) was cloned into the plasmid pHsh from Thermotoga maritima, and expressed in Escherichia coli JM 109. The recombinant protein was purified to homogeneity by a simple step, heat treatment. The recombinant enzyme had a molecular mass of 33 kDa. The optimal temperature and pH of Tm-LDH were observed 95 degrees C and 7.0. The purified enzyme had a half-life of 2 h at 90 degrees C, and exhibited better stability over a pH range from 5.5 to 8.0. The K(m) and V(max) values were 1.7 mmol/L, 3.8 x 10(4) U/mg of protein for pyruvate, and 7.2 mmol/L and 1.1 x 10(5) U/mg for NADH, respectively. The expression of Tm-LDH in T7 system could not obtain high efficiency, but it has been soluble over-expression in pHsh system and reached 340 mg/L. The superior stability and productivity of Tm-LDH will lay the foundation of its industrial-scale fermentation and application in the NAD regeneration.

Advances in and challenges for thermophilic fermentation of cellulosic ethanol / 生物工程学报

Thermophiles can produce cellulosic ethanol at a high temperature where ethanol is directly distillated from fermentation, and biodegradation of lignocellulose can be simultaneously achieved when these thermophiles carry and express cellulase and hemicellulase genes. The simultaneous biodegradation, fermentation and distillation, a three-in-one process, can result in low production costs of cellulosic ethanol. We reviewed the advances and challenges in the approach to the three-in-one process, which refer to lignocellulases, regulation mechanisms, and genetic transfer systems.

Expression, purification and characterization of a thermostable pectate lyase from Thermotoga maritima / 生物工程学报

The structure gene pelA from Thermotoga maritima MSB8 encoding pectate lyase was amplified and ligated into pHsh, resulting pHsh-pelA. Through structural optimization on pHsh-pelA, the ultimate plasmid, pHsh-pelC, which possessed the most appropriate structure and free energy of mRNA, was obtained. Pectate lyase C (PelC) was obtained after expressing pHsh-pelC in Escherichia coli JM109. The optimum activity of PelC was determined at pH 8.5 at 90 degrees C, with a half-life for almost 2 h at 95 degrees C. PelC was stable at the pH range of 8.2-9.8, and was dependent on Ca2+ for activity and stability. The enzyme kept stable for a long time and possessed a high level of activity at 60 degrees C. The kinetic assay using polygalacturonic acid (PGA) as substrate gave K(m) and V(max) of 0.11 mmol/L and 327 U per mg of protein. SDS-PAGE analysis showed that the molecular mass of the expressed recombinant PelC was about 43 kD, which was exactly the size predicted. The expression vector system of the heat shock plasmid pHsh owned such advantages as high expression level and cheap induction. Moreover, the superior stability of the recombinant enzyme laid the base for large-scale fermentation application.

Expression, characterization and application of thermostable beta-glucuronidase from Thermotoga maritima / 生物工程学报

The gene of beta-glucuronidase from Thermotoga maritima was cloned into the plasmid pHsh, and expressed in Escherichia coli JM109. The recombinant protein was purified to homogeneity by a simple step, heat treatment. The recombinant enzyme had a molecular mass of 65.9 kD. The optimal activity of beta-glucuronidase was found at pH 5.0 and 80 degrees C. The purified enzyme was stable over a pH range from 5.8 to 8.2 and had a half life of 2 h at 80 degrees C. The kinetic experiments at 80 degrees C with p-nitrophenyl-beta- glucuronide as substrate gave a K(m) and V(max) of 0.18 mmol/L and 312 u per mg of protein. The purified enzyme could transform glycyrrhizin to glycyrrhetinic acid.

REVIEW OF STUDIES ON ARABINOFURANOSIDASES / 微生物学通报

Hemicellulose is a kind of very abundant carbohydrate,which is not y ot exploited Arabinofuranosidase is important enzyme in biodegradation of hemi cellulose Up to now many arabinofuranosidases and genes have been studied in t he world In this paper, we reviewed mainly on the classification, characterizati on, utility and gene expression of arabinofuranosidase

STUDY ON RESISTANCE GENE KNOCK OUT FROM INTEGRATED ALKALINE PROTEASE GENE ENGINEERING STRAIN / 微生物学通报

The knock out vector pHK was constructed with E coli vector pET 28a and shuttle vector pHY300PL, by using denatured DNA and homologous recombination technique, the kanamycin resistance gene ( Kan r) from integrated alkaline protease gene engineering strain BP071 was knocked out successfully, and the 11 positive clones were obtained The yield of the best positive clone BP0715 was stable as same as BP071 The methods provided the good experience for the industrial microbiology research, and it was foundation for studying on the safety of genetically modified organisms