min and stands at 2 8 u00b0 c for 10 hours then the supernatant is taken for hplc detection the content of recombinant insulin glargine in the supernatant is as low as 0 02 mg ml and meets the requirements about 77l of the supernatant is decanted and the remaining 7l of suspension is respectively added to 1l centrifuge bottle and centrifuged at 4000 rpm for 10 min after configuration the crystal precipitates are removed from all of the centrifuge bottles and suspended in 0 02m ammonium acetate solution at a concentration of 20 g l the suspension is adjusted to ph value of 7 8 washed centrifuged again to collect the crystal precipitate washed again and then centrifuged again for removing the supernatant after freeze drying for 40 hours 245 6 g of freeze dried powder is obtained with water content of 2 3 water is added to the freeze dried powder to form a suspension for microscopic examination a number of uniform and regular hexahedron crystals can be seen at magnification of 160 and the transparency is high see fig2 recombinant insulin glargine crystallization solution is prepared by using the same method as example 1 in which the components and the concentrations.