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1.
Vacuolar sequestration of valuable secondary metabolites remains the major limitation to the use of immobilization technology for large scale plant-cell-based bioprocesses, which otherwise may be a more efficient culture system than suspension for this biomass. In this initial study, the release of indole alkaloids produced by immobilized Catharanthus roseus cells cultured in Zenk's Alkaloid Production Medium was evaluated. Unstimulated alkaloid release in immobilized cultures reached levels of 10 to 50% of total production or 3 to 100% of known alkaloid content (30 to 4700 micrograms l-1), which was higher than that found for suspension cultures of the cell line used (10 to 25% of total production) without apparent cell lysis. Modifications of the medium pH value of immobilized cultures were explored in order to improve this release. Periodical additions of acid (HCl 0.1 N) or base (KOH 0.1 N) solutions (2% v/v) to different cultures resulted in rapid (less than 3 h) and transient variations in extracellular pH value from 5.5 to 4.3, and 5.8 to 8.5, respectively. In both cases, these variations provoked significant increase in total alkaloid (from approximately 5-10 mg l-1 to 15 mg l-1), ajmalicine (from 0 to approximately 0.29 mg l-1) and serpentine (from 0 to approximately 0.20 mg l-1) release, without apparent cell lysis or decrease in the culture viability. This product release was estimated to represent 100% of alkaloids produced. 相似文献
2.
Summary The plasmid pRH271, harboring a xylanase gene cioned fromBacilius
subtilis, has been transferred into a mutant ofE.
coli SK2284 which allowed the release of part of the xylanase in the culture supernatant. Kinetic parameters of this recombinantE.
coll strain were determined in microscale batch culture with and without the selective pressure of antibiotics. No significant difference in µmax was observed for the nontransformedE.
coli strain when compared to the recombinant strain. However, K5 values for glucose were two times higher in the case of the recombinant strain. Preliminary study of xylanase production in a large batch farmenter was also described. 相似文献
3.
The anatomical variation of orthotropic elastic moduli of the cancellous bone from three human proximal tibiae was investigated using an ultrasonic technique. With this technique, it was possible to measure three orthogonal elastic moduli and three shear moduli from cubic specimens of cancellous bone as small as 8 mm per side. Correlation with mechanical tensile testing has shown this technique to offer a precise measure of cancellous modulus (Eten = 0.94Eult + 144.6 MPa, r2 = 0.96, n = 34). The cancellous bone of the proximal tibia was found to be very inhomogeneous, with the axial modulus ranging between 340 and 3350 MPa. A course map is presented, showing measured Young's moduli as a function of anatomical position. The anisotropy of the cancellous bone, determined by the relative differences between the three orthogonal moduli, was shown to be relatively constant over the entire range of cancellous densities tested. The relationship between the axial elastic modulus and the apparent density was found to be approximately linear, as reported by others for proximal tibial cancellous bone. 相似文献
4.
5.
To localize the DNA binding domain of the Saccharomyces cerevisiae Ars binding factor 1 (ABF1), a multifunctional DNA binding protein, plasmid constructs carrying point mutations and internal deletions in the ABF1 gene were generated and expressed in Escherichia coli. Normal and mutant ABF1 proteins were purified by affinity chromatography and their DNA binding activities were analyzed. The substitution of His61, Cys66 and His67 respectively, located in the zinc finger motif in the N-terminal region (amino acids 40-91), eliminated the DNA binding activity of ABF1 protein. Point mutations in the middle region of ABF1, specifically at Leu353, Leu399, Tyr403, Gly404, Phe410 and Lys434, also eliminated or reduced DNA binding activity. However, the DNA binding activity of point mutants of Ser307, Ser496 and Glu649 was the same as that of wild-type ABF1 protein and deletion mutants of amino acids 200-265, between the zinc finger region and the middle region (residues 323-496) retained DNA binding activity. As a result, we confirmed that the DNA binding domain of ABF1 appears to be bipartite and another DNA binding motif, other than the zinc finger motif, is situated between amino acid residues 323 and 496. 相似文献
6.
Association of adenovirus type 2 early proteins with a soluble complex that synthesizes adenovirus DNA in vitro 总被引:3,自引:0,他引:3
H M Rho Y H Jeng W S Wold M Green 《Biochemical and biophysical research communications》1977,79(2):422-428
A soluble Ad2 DNA synthesizing complex was prepared from Ad2-infected KB cell nuclei and purified by exclusion chromatography on a BioGel A-50m column. The purified complex was able to synthesize DNA from all regions of the virus genome, as indicated by RI restriction endonuclease analysis of labeled DNA. Experiments were performed to identify Ad2-induced early polypeptides present in the complex. Ad2-infected and mock-infected cells were labeled with [35S]methionine 7–10 h postinfection, then incubated for 8 h to allow the 35S-labeled early polypeptides to become associated with the complex. The polypeptides in the purified complex and each of the cell fractions were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. The major components of the purified complex were the 73K DNA binding phosphoprotein and 11K, two adenovirus 2-induced early polypeptides. The 11K has a preferred nuclear location. Small quantities of other Ad2-induced early proteins, 21K, 15K, and possibly 8.3K were also associated with the complex. 相似文献
7.
Joon H. Rho 《Analytical biochemistry》1980,105(1):414-423
We have examined the metabolites produced by in vitro incubation of benzo(a)pyrene with 3-methylcholanthrene-induced mice liver microsomes. Our objective was to observe directly a possible difference in microsomal enzyme systems of animal models having different susceptibility to chemical carcinogens. The metabolites produced by the two animal models, and mice, were analyzed by a highly sensitive, “three-dimensional” fluorescence plotting technique. The fluorescence spectra of the total ethyl acetate-soluble metabolites clearly indicate that the metabolites produced by enzymes were predominantly monohydroxylated benzo(a)pyrene while those produced by the liver microsomes of were highly enriched with the 7,8-dihydrodihydroxybenzo(a)pyrene type. 相似文献
8.
The aerobic metabolism of cyclohexanecarboxylic acid by Acinetobacter anitratum. 总被引:1,自引:0,他引:1 下载免费PDF全文
1. The aerobic metabolism of cyclohexanecarboxylic acid by a bacterium isolated from garden soil (Acinetobacter anitratum) was investigated. 2. Evidence for the formation of cyclohex-1-ene-1-carboxylate, 2-hydroxycyclohexanecarboxylate and pimelate when either cell suspensions or cell-free extracts were incubated in the presence of cyclohexanecarboxylic acid is presented. 3. Crude cell-free extracts required ATP, CoA, FAD and Mg2+ as cofactors for the production of pimelate from cyclohexanecarboxylic acid, suggesting the existence of an activating reaction with formation of CoA esters, in this system. 相似文献
9.