We previously screened and obtained a novel pyrethroid-hydrolyzing gene sys 410 from Turban Basin metagenomic library

which was expressed in E coli BL21 (DE3) in soluble form. Here

to enhance the production and activity of the enzyme

flaskshaking medium and fermentation condition were investigated. The optimum medium was as follows: glycerol 20.0 g·L

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yeast extract 20.0 g·L

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ammonium sulfate 8.0 g·L

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phosphate 100.0 mmol·L

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magnesium sulfate 5.0 mmol·L

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trace element solution 1.5 mL·L

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. The optimum conditions of flaskshaking fermentation were as follows: loading volume 50/250 (V/V)

initial medium pH 7.0

inoculum size 2%

lactose induction for 6 h. We also studied highdensity fermentation of the recombinant strain in 75 L fermenter. The results showed that dispersed oxygen supply

low concentration of the initial medium

and carbon and nitrogen fedbatch culture could stimulate the growth of the recombinant strain. Inducible expression started at the middle and later stages of logarithmic growth with 6 g·L

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lactose at 37 ℃. After 10 h

cell density reached 142.6 and the enzymatic activity was 3 105.1 U·mL

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13.7 and 31.9 times better than those of the flaskshaking fermentation

respectively. In addition

crude enzyme powder was obtained after sonication and freeze drying with the amount of 68.4 g·L

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of fermentation broth. The specific enzyme activity was 119 426.9 U·g

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Remarkably

the enzyme was able to efficiently degrade all tested pyrethroids within 15 min

reaching over 95% conversion.