As a type of prebiotics and dietary fiber, inulin performs plenty of significant physiological functions and is applied in food and pharmaceutical fields. Inulosucrase from microorganisms can use sucrose as the substrate to synthesize inulin possessing higher molecular weight than that from plants. In this work, a hypothetical gene coding inulosucrase was selected from the GenBank database. The catalytic domain was remained by N- and C- truncation strategies, constructing the recombinant plasmid. The recombinant plasmid was expressed in E. coli expression system, and after purifying the crude enzyme by Ni²⁺ affinity chromatography, a recombinant enzyme with a molecular weight of approximately 65 kDa was obtained. The optimal pH and temperature of the recombinant enzyme were 5.5 and 45 °C, respectively, when sucrose was used as the sole substrate. The activity of this enzyme was inhibited by various metal ions at different degrees. After purifying the produced polysaccharide, nuclear magnetic resonance analysis was used to determine that the polysaccharide was inulin connected by β-(2,1) linkages. Finally, the conditions for the production of inulin were optimized. The results showed that the inulin production reached the maximum, approximately 287 g/L after 7 h, when sucrose concentration and enzyme dosage were 700 g/L and 4 U/mL, respectively. The conversion rate from sucrose to inulin was approximately 41%.
Escherichia coli/genetics* ; Hexosyltransferases/genetics* ; Inulin ; Oligosaccharides ; Sucrose

Objective To establish a simultaneous detection approach for 34 emerging contaminants(ECs)in tap water by liquid chromatography-tandem mass spectrometry(HPLC-MS/MS).Human health risk assessment was performed according to the detection results from 43 tap water samples.Methods Tap water samples were concentrated and extracted by solid phase extraction,and then blown to near dry by nitrogen at 40℃.The sample extracts were dissolved in methanol-water solution(95:5,VN)to 0.5 mL for analyzing.Agilent Jet Stream Electrospray Ionization(AJS ESI)and the multiple reaction monitoring(MRM)mode were performed for MS to acquire the data of 34 ECs.A database including precursor ion,product ion and retention times was established accordingly.Results The average linear correlation coefficients(r)of 34 kinds of ECs was 0.995 9.The limits of detection were 0.01～0.60 ng/L and the recoveries were between 60.7％and 119.8％.The intra-group precisions were between 0.05％～9.89％and the intra-day precisions were between 0.20％～14.40％for the spiked samples.The method was applied to analyze 43 tap water samples and a total of 15 ECs were detected.According to the results,the detection rate of caffeine was the highest(84％),and the concentration range was ND～74.42 ng/L.Among all the ECs detected,1,2,3-benzotriazole had the highest concentration(ND～361.15 ng/L),where detection rate was 44％.Humans may be exposed to these ECs by drinking the tap water.The human health risk assessments of 12 kinds of ECs were carried out,however,the estimated risk was negligible(risk quotient＜0.01).Conclusion The method is simple,highly sensitive and selective,and could meet the detection needs of ECs at trace level in tap water.There was no human health risk posed for ECs identified in 43 tap water samples analyzed by this method.

Objective:To explore the relationship between bullying and depressive symptoms in college students,the mediating role of mobile phone addiction and the moderating role of gender.Methods:Totally 1 499 college students in Nantong City were selected to evaluate bullying experience,mobile phone addiction tendency and depressive symptoms with the Revised Adolescent Peer Relations Instrument-Bully and Target(RAPRI-T),Smart-phone Addiction Scale-Short Version(SAS-SV),Patient Health Questionnaire Depression 9-item(PHQ-9).SPSS macro program PROCESS 3.2 was used to examine the mediating role of mobile phone addiction and the modera-ting role of gender.Results:Different forms of bullying,traditional verbal bullying had the highest detection rate.There were positive correlations among bullying and the scores of SAS-SV and PHQ-9(r=0.17-0.42,Ps＜0.001).In the relationship between bullying scores and PHQ-9 scores,SAS-SV scores played a partial mediating role,and the mediating effect accounts for 26.70％of the total effect.The interaction terms between bullying and genders had statistical significance with PHQ-9 scores(β=0.09,P＜0.001),as the bullying scores increased,the PHQ-9 scores were higher in girls than in boys.Conclusion:Mobile phone addiction plays a partial mediating role in the association between bullying and depressive symptomsin college students,and the association between bull-ying and depressive symptoms is moderated by gender factors.