The cis-epoxysuccinate hydrolase (CESH) from Rhizobium strain BK-20 is the key enzyme for L(+)-tartaric acid production. To establish a highly efficient and stable production process, we first optimized the enzyme production from Rhizobium strain BK-20, and then developed an immobilized cell-culture process for sustained production of L(+)-tartaric acid. The enzyme activity of free cells reached (3 498.0 +/- 142.6) U/g, and increased by 643% after optimization. The enzyme activity of immobilized cells reached (2 817.2 +/- 226.7) U/g, under the optimal condition with sodium alginate as carrier, cell concentration at 10% (W/V) and gel concentration at 1.5% (W/V). The immobilized cells preserved high enzyme activity and normal structure after 10 repeated batches. The conversion rate of the substrate was more than 98%, indicating its excellent production stability.
Alginates ; chemistry ; Cells, Immobilized ; Glucuronic Acid ; chemistry ; Hexuronic Acids ; chemistry ; Hydrolases ; metabolism ; Rhizobium ; enzymology ; metabolism ; Tartrates ; metabolism

Objective: To understand epidemiological characteristics of the pathogens and evolution of the genotype associated with infectious diarrhea epidemic caused by norovirus in Hebei Province. Methods: A total of 8 infectious diarrhea outbreaks caused by norovirus were reported from Jan 2015 to Dec 2016, of which epidemic treatment materials and specimens were collected at the same time. Norovirus nucleic acid was detected by using real-time PCR, and the partial ORF2 of the all positive specimens were amplified by RT-PCR and sequenced. Phylogenetic tree was constructed by using Mega5.2 based on partial ORF2 sequences of norovirus to perform phylogenetic analysis. Results: A total of 8 norovirus outbreaks, involving 265 cases who were mainly for residential inhabitents, children and students, were reported during this period, and the overall attack rate ranged from 0.70% to 8.13%. The overall positive detection rate of norovirus was 66.25%. The PCR products were sequenced, and sequencing result were obtained for 28 samples, which included GⅠ.3, GⅡ.2, GⅡ.4, GⅡ.13 and GⅡ.17. Conclusions Multiple genotypes of infectious diarrhea outbreaks caused by norovirus were found in Hebei province.