ABSTRACT
A whole-cell catalyst using Escherichia coli BL21(DE3) as a host, expressing L- threonine dehydratase from Escherichia coli, and co-expressing leucine dehydrogenase from Bacillus cereus and glucose dehydrogenase from Bacillus subtilis for cofactor regeneration, was constructed and used for one-pot production of L-2-aminobutyric acid (L-ABA) and D- gluconic acid from L-threonine and D-glucose. We used shake-flask culture to study the whole-cell catalytic condition including temperature, pH, proper permeabilization of cells and optimal wet cells amount. Moreover, the whole-cell catalyst was cultured in 5-L fermentor by fed-batch fermentation, and 164 g/L L-threonine and 248 g/L D-glucose were converted to 141.6 g/L L-ABA and 269.4 g/L D-gluconic acid. The whole-cell catalyst is promising to fulfill industrial requirements for L-ABA and D-gluconic acid.
ABSTRACT
Objective To determin the amino acids in silkworm extract by High Performance Liquid Chromatography with Precolumn Derivatization.Methods With the technology of precolumn derivatization, along with high performance liquid DABS-CL and a high-efficiency YMC-Pack ODS-A column(250?4.6mm, 5 ?m), with mobile phase being A:25mol/L KH2PO4 and B: acetonitrile : methyl alcohol =70:30, at flow rate of 1.5 ml/min, peaks were detected at 436nm and column temperature being 35℃.Results All kinds of amino acids have a nice linear relations (r=0.9989~0.9999), precision (RSD
ABSTRACT
Objective To set up a simple and accurate method for the determination of total Glucosides in Paeonia lactifloria (TGP) by HPLC.Methods Benzoic acid being as contiol,the amounts of TGP were obtained from the following formula :TGP( ) = benzoic acid() ?480. 27/ 121. 121. Benzoic acid was determined by HPLC. Chromatographic conditions concluded YMC-Pack ODS-A(5?m,150?4.6mm)column and the mobile phase consisting a mixture of MeOH - 0.05mol?L - 1KH2PO4 - HAC - isopropanol (85:155:4:6). Benzoic acid was detected at 230nm wavelength.Results The calibration curves of Benzoic acid were in good linearity over the range of 0.1~2g(r=1.0000). The average recovery of Benzoic acid was 101.12(n=9,RSD=2.49). Conclusion This method is simple and can be easily repeated.
ABSTRACT
Objective To set up a simple and accurate method for the determination of saikosaponins in Bupleurum chinense DC. by UV-Visible Spectrophotometry. Methods The content of saikosaponins was determined by UV-Visible Spectrophotometry. The absorbency was measured at 536nm. Results The calibration curves was linear within 194~1940mg/L(r=0.9996). The average recovery was 97.35%,and the RSD was 1.02%(n=9). Conclusion The method was proved to be simple, precise and reproduciable. It can be used for the quantitative determination of B upleurum chinense DC.