Degradation of Polysaccharide from Porphyridium Cruentum and Its Antioxidant Activities in vitro

The expression of recombinant protein HIV-TATm-Survivin (T34A) by E.coli BL21(DE3) decreased significantly in long-time preservation, which usually led to difficulty in scale up and process improvements. In this study, adaptive evolution experiments of the host cells were conducted under the stress from background expression, and two distinct strains, E. coli BL21(DE3) HTS1 and HTS2 with the same plasmid pRSET-B-TAT-Survivin (T34A), were finally obtained. In shake flask cultivations, the strain HTS1 showed a higher growth rate but a poor capacity of protein expression; in contrast, strain HTS2 grew a little bit slowly but could overexpress the target protein. We proposed that the appearance of strain HTS1 was responsible partly for the protein expression decrease during the preservation. Furthermore, strain HTS2 was advantageous in the scale-up process, the overexpression of HIV-TATm- Survivin (T34A) by it did not negatively affected by up to 300 mmol/L sodium acetate, and such results were further confirmed in the 4 L and 30 L fermentors.