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Objective: Investigating the antioxidant activities of water and ethanol extracts of natural Cordyceps sinensis and Cordyceps militaris and their fermentation preparations., Method: The samples were tested through 6 assays: inhibition ability of linoleic acid oxidation; scavenging activity of DPPH, hydrogen peroxide, hydroxyl radical and superoxide anion; and metal chelating activity., Result: Samples showed different antioxidant ability, and there was not an extract that exhibited high activity in all assays; however, water extract of natural C. militaris could be regarded as the most powerful antioxidant among 8 samples. It had high activity in inhibition of linoleic acid oxidation, chelating metal ions, and scavenging DPPH and hydroxyl radical. The research also indicated that the contents of phenolic compounds in water and ethanol extracts of natural and cultured Cordyceps sp. had huge difference., Conclusion: Natural Cordyceps sp. and its fermentation preparations could be used as potential natural antioxidants. The fermented process affected the antioxidant ability of cultured Cordyceps sp., and the antioxidant activity of both natural and cultured Cordyceps sp. did not significantly related with the quantity of phenolics.

Recombinant bacteria exhibiting high enzymatic activities were obtained by cloning and coexpression of both caiB gene and caiE gene in the host of E. coli Bl21(DE3), which encode carnitine dehydratase and a protein related to the synthesis of cofactor for carnitine dehydratase, respectively. In order to coexpress these two genes, compatible and incompatible two plasmids system were used, the difference between them was also studied. After induction with IPTG, both caiB and caiE genes were coexpressed in both compatible two plasmids system and incompatible two plasmids system. In the former system, the expressed products accounted for 17% and 10% of the total proteins in the host; in the later system, the proportion was 39% and 20%, respectively. The activity of carnitine dehydratase in E. coli Bl21(DE3) with either coexpression system is about 2.3 times than that in E. coli Bl21(DE3) with only pET28-caiB. The plasmids stabilities in these two systems were the same, all needed the help of antibiotic selective pressure.

The cDNA encoding the human copper, zinc-superoxide dismutase(Cu, Zn-SOD) was amplified from the human liver by RT-PCR and sequenced. The cloned human Cu, Zn-SOD cDNA was ligated into expression vector pET-22b(+) under T7 promotor. After 3 h induction with 1 mmol/L IPTG, human Cu, Zn-SOD was highly expressed in E.coli BL21(DE3). The expression product was up to 30% of the total protein of the bacteria in soluble form, which had specific SOD activity.