Double Plasmids

We tested the affection ofβ-glucosidase induced by IPTG(1000mM) and Ara(1000mM) on 96-well plates and measuring the A450(pNPG decomposed as substrate to pNP which can be detected at 450nm) every one hour. After collected data, we output a graph of A450-time.

We analysised the pet28a-βglu plasmid and pSB1C3-T7RNAp plasmid in double-plasmid E. coli, and using JDesigner we set up the model of the expression toβ-glucosidase . This model displayed the process of pNPG’ decomposition in wells.

Set parameters as：Lac=1000, Ara=1000, pNPG=13 and export the graph to pNPG-time. Modify the parameters(k1, k2_Vmax, k2_Km, k2_Ki, k3_1, k3_2,k4, k5) until the curve fit to the graph output from origin data.

In this result, the parameter (k1, k2_Vmax, k2_Km, k2_Ki, k3_1, k3_2, k4, k5) is 1, 3.4, 2.9, 0.4, 1, 96000.

Enzyme activity

β-galactosidase is used to deglycosylate saponin of notoginseng. Our Lab have a PET-28a plasmid withβ-galactosidase gene and LacI gene. The transcription of β-galactosidase is repressed by LacI protein. But lactose and IPTG can induce the expression of LacI protein. We used a 3L fermentation tank to conduct preliminary experiments, then the enzyme was extracted from bacteria solution using glycine buffer. The result showed us that extracted solution has strong ability to hydrolyze glycosyl. However, there’s no lactose in notoginseng solid medium. In order to reduce costs, another plasmid psb1C3 which contains T7 RNA Polymerase gene and was transformed into E.coli. Psb1C3 contains T7 RNA Polymerase gene and can be regulated by pBAD. This double-plasmid system is expected to be regulated by pPAD, and expresses a large number of T7RNA polymerase to inhibit the effect of LacI repression, switch on the expression ofβ-galactosidase. It’s been reported in bibliography that the cellwall of notoginseng contains a certain concentration of arabinose. Our ultimate goal is using notoginseng to provide nutrients for E.coli in a solid state fermentation jar, E.coli can deglycosylate saponin of notoginseng as well.