Purpose　The aim is to optimize the liquid culture conditions of dihydropyrimidinase producing strain Pseudomonas putida 9801. Methods　Plackett-Burman design and spherical symmetric desig n were used.Results　Optimum conditions for dihydropyrimidinas e formation of Pseudomonas putida 9801 were defined:yeast extract 2.39%, Glu cose 1.81%,Uracil 0.06%,K2HPO4*3H2O 0.2%, MgCl2*6H2O 0.05%and NaCl 0 .3%,when the strain was cultured at 32℃ for 10 h,about 3.02 units/ml of hydanto inase was obtained. This value was quite consistent with the theory value(2.91 u nits/ml).Conclusion　The liquid culture conditions of dihydrop yrimidinase producing strain were optimized.

A new fusion expression vector, pED-P8-Hi-lys was designed and constructed. It includes four parts, a 20 peptide sequence of hirudin that can maintain anticoagulant activity, the C-terminus of asparaginase as a fusion partner, basic octopeptide (KRKRKKSR) that makes the fusion partner easy to remove, and the unique acid-labile aspartyl-prolyl bond. It was transformed into E. coli BL-21 and the fusion protein (AnsB-C-P8-Hi-lys) was expressed effectively as inclusion bodies after inducing by lactose. The objective peptide Hi-lys was purified by means of cell disruption, washing, ethanol precipitation, acid hydrolysis, and DEAE-cellulose 52 column chromatography. The antithrombin activity of the purified Hi-lys peptide was about 50 ATU/mg by thrombin activity assays.

AIM　The purpose is to construct D-hydantoinase genetic engineering strain for the purpose of the industrial production of D-p-hydroxyphenylglycine. METHODS　D-hydantoinase gene was created from Pseudomonas putida 9801 by PCR technique and inserted into pMD18-T vector. The recombinant plasmid was transformed into several Escherichia coli strains. The positive transformants with D-hydantoinase activity were obtained by the two step screening, digoxigenin DNA labeling in situ hybridization and D-hydantoinase activity assay. RESULTS　The D-hydantoinase activity of the genetic engineering strain E.coli BL21/pMD-dht was 1700 U*L-1 and increased as high as 8 times compared with those of wild-type strain Pseudomonas putida 9801. The subunit molecular weight of recombinant D-hydantoinase was about 53 kDa measured by SDS-PAGE. The amount of the recombinant D-hydantoinase was about 20 percent of total bacterial soluble proteins. CONCLUSION　The genetic engineering strain E.coli BL21/pMD-dht possesses the initial industrial production prospects.

Major infectious disease epidemic continues to pose a threat to human health and society, and the effective establishment and implementation of an early warning system plays a key role in addressing public health security risks. At present, the research on early warning of infectious diseases in the academic community mainly focuses on early warning information system, early warning mechanism, laws and regulations of early warning of infectious diseases, and some studies lack specific suggestions on operation methods. By collating and summarizing the literature from 2002 to 2022, regarding the early warning system and mechanism of major infectious diseases, this paper focused on analyzing the public health ethical dilemmas existing in the early warning process and discussing how to strengthen the construction of the early warning system of infectious diseases, so as to lay the foundation for creating more scientific early warning schemes of infectious diseases.