The microbial production of D-lysine to replace chemical approach has gained great interest with the rising concerns over the environment.Here,we employed recombinant E.coli strain BL21-LYR with lysine racemase and st...The microbial production of D-lysine to replace chemical approach has gained great interest with the rising concerns over the environment.Here,we employed recombinant E.coli strain BL21-LYR with lysine racemase and strain BL-22A-RB-YB with L-lysine monooxygenase and 5-aminovaleramide amidohydrolase to establish a two-strain coupling whole-cell bioconversion system for D-lysine production from L-lysine.To improve the optical purity of D-lysine,the optimal reaction condition for resolution of DL-lysine after the racemization was investigated.The specificity of BL-22A-RB-YB for L^-lysine and the effects of reaction condition on bioconversion efficiency of whole-cell were accordingly determined.Under the optimal condition,a maximum 53.5 g·L^-1 D-lysine and 48.2 g·L^-15-AVA were obtained with yield of 47.4%and 42.3%,respectively,by the microbial racemization and asymmetric degradation process.The final D-lysine enantiomeric excess was over 99%.Meanwhile,a valuable compound 5-aminovaleric acid was synthesized with the production of D-lysine,indicating the economic feasibility of the two-strain coupling system.展开更多
A total of 900 one-d-old Chinese Huainan Partridge Shank chickens were randomly allocated into nine groups with five replicates of 20 each.Birds were fed with basal diet,basal diet supplemented with 150 mg kg^（–1） ...A total of 900 one-d-old Chinese Huainan Partridge Shank chickens were randomly allocated into nine groups with five replicates of 20 each.Birds were fed with basal diet,basal diet supplemented with 150 mg kg^（–1） aureomycin,basal diet supplemented with different proportions of Bacillus licheniformis and Bacillus subtilis,which was 0：1.0×10~6,2.5×10~5：7.5×10~5,3.3×10~5：6.6×10~5,5.0×10~5：5.0×10~5,6.6×10~5：3.3×10~5,7.5×10~5：2.5×10~5 and 1.0×10~6：0,respectively.The duration of the experiment was 56 d.The results indicated that dietary supplementation of 6.6×10~5：3.3×10~5 of B.lichenifornis：B.subtilis improved final body weight,increased the average daily gain,and reduced feed/gain ratio（P〈0.05）.The numbers of total Lactobacillus and Bifidobacterium sp.in the caecum significantly increased,and the numbers of Escherichia coli and Salmonella sp.significantly declined compared to that of the control（P〈0.05）.Intestinal villous height and villous height to crypt depth ratio of the duodenum,jejunum,and ileum were significantly higher than that of the control,and intestinal crypt depth of the duodenum and ileum was significantly lower（P〈0.05）.The total antioxidant capacity,total superoxide dismutase,and glutathione peroxidase ability in plasma significantly improved,while the malondialdehyde concentration in plasma decreased（P〈0.05）.Compared to the control,plasma concentrations of ammonia,uric acid and urea nitrogen and the activity of xanthine oxidase were reduced（P〈0.05）.In conclusion,an inclusion of 6.6×10~5：3.3×10~5 of B.licheniformis：B.subtilis to the diet improved the growth performance,caecal microbiota,plasma biochemical profile,and significantly improved the small intestine morphology,while reducing the mortality rate.展开更多
We propose a malaria model involving the sensitive and resistant strains,which is described by reaction-diffusion equations.The model reflects the scenario that the vector and host populations disperse with distinct d...We propose a malaria model involving the sensitive and resistant strains,which is described by reaction-diffusion equations.The model reflects the scenario that the vector and host populations disperse with distinct diffusion rates,susceptible individuals or vectors cannot be infected by both strains simultaneously,and the vector population satisfies the logistic growth.Our main purpose is to get a threshold type result on the model,especially the interaction effect of the two strains in the presence of spatial structure.To solve this issue,the basic reproduction number(BRN)R_(0)^(i)and invasion reproduction number(IRN)R_(0)^(i)of each strain(i=1 and 2 are for the sensitive and resistant strains,respectively)are defined.Furthermore,we investigate the influence of the diffusion rates of populations and vectors on BRNs and IRNs.展开更多
The emergence of a novel strain during a pandemic,like the current COVID-19,is a major concern to the healthcare system.The most effective strategy to control this type of pandemic is vaccination.Many previous studies...The emergence of a novel strain during a pandemic,like the current COVID-19,is a major concern to the healthcare system.The most effective strategy to control this type of pandemic is vaccination.Many previous studies suggest that the existing vaccine may not be fully effective against the new strain.Additionally,the new strain's late arrival has a significant impact on the disease dynamics and vaccine coverage.Focusing on these issues,this study presents a two-strain epidemic model in which the new strain appears with a time delay.We considered two vaccination provisions,namely preinfection and post-infection vaccinations,which are governed by human behavioral dynamics.In such a framework,individuals have the option to commit vaccination before being infected with the first strain.Additionally,people who forgo vaccination and become infected with the first train have the chance to be vaccinated(after recovery)in an attempt to avoid infection from the second strain.However,a second strain can infect vaccinated and unvaccinated individuals.People may have additional opportunities to be vaccinated and to protect themselves from the second strain due to the time delay.Considering the cost of the vaccine,the severity of the new strain,and the vaccine's effectiveness,our results indicated that delaying the second strain decreases the peak size of the infected individuals.Finally,by estimating the social efficiency deficit,we discovered that the social dilemma for receiving immunization decreases with the delay in the arrival of the second strain.展开更多
Background： Human immunodeficiency virus isolates most often use chemokine receptor CCR5 or CXCR4 as a coreceptor to enter target cells. During early stages of HIV-1 infection, CCR5-tropic viruses are the predominant...Background： Human immunodeficiency virus isolates most often use chemokine receptor CCR5 or CXCR4 as a coreceptor to enter target cells. During early stages of HIV-1 infection, CCR5-tropic viruses are the predominant species. The CXCR4-tropic viruses may emerge late in infection. Recognition of factors influencing this phenotypic switch may give some hints on the antiviral strategies like anti-H1V/AIDS drugs, gene therapy and vaccines. Methods： To investigate the mechanism that triggers R5 to X4 phenotypic switch, we performed a systematic sensitivity analysis based on a five-dimensional model with time-varying parameters. We studied the sensitivity of each factor to the CCR5-to-CXCR4 tropism switch and acquired some interesting outcomes beyond expectation. Results： The death rate of free virus （dv）, rate that uninfected CD4＋ T cells arise from precursors （s） and proliferate as stimulated by antigens （r）, and in vivo viral burst size （N） are four robust factors which are constantly observed to have a strong correlation with the evolution of viral phenotype for most patients longitudinally. Conclusions： Crucial factors, which are essential to phenotypie switch and disease progression, are almost the same for different patients at different time points, including the production of both virus and CD4＋ T cells and the decay of virion. It is also worth mentioning that although the sequence of factors sorted by the influence varies between patients, the trends of influences engendered by most factors as disease progresses are similar inter-patients.展开更多
In this paper, we propose a two strain epidemic model with single host population. It is assumed that strain one can mutate into strain two. Also latent-stage progression age and mutation are incorporated into the mod...In this paper, we propose a two strain epidemic model with single host population. It is assumed that strain one can mutate into strain two. Also latent-stage progression age and mutation are incorporated into the model. Stability of equilibria （including the disease free equilibrium, dominant equilibria and the coexistence equilibrium） is investigated and it is found that they are locally stable under suitable and biological feasible constraints. Results indicate that the competition exclusion and coexistence of the two strains are possible depending on the mutation. Numerical simulations are also performed to illustrate these results.展开更多
基金financial supports from the National Natural Science Foundation of China(Grant No.21908099)the National Key Research and Development Program of China(Grant No.2016YFA0204300)+2 种基金Key Research and Development Program(Social Development)Project Jiangsu Province(Grant No.BE2018730)the Natural Science Research Projects of Colleges and Universities in Jiangsu Province(Grant No.18KJB530009)the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture(Grant No.XTB1802,Grant No.XTE1846)。
文摘The microbial production of D-lysine to replace chemical approach has gained great interest with the rising concerns over the environment.Here,we employed recombinant E.coli strain BL21-LYR with lysine racemase and strain BL-22A-RB-YB with L-lysine monooxygenase and 5-aminovaleramide amidohydrolase to establish a two-strain coupling whole-cell bioconversion system for D-lysine production from L-lysine.To improve the optical purity of D-lysine,the optimal reaction condition for resolution of DL-lysine after the racemization was investigated.The specificity of BL-22A-RB-YB for L^-lysine and the effects of reaction condition on bioconversion efficiency of whole-cell were accordingly determined.Under the optimal condition,a maximum 53.5 g·L^-1 D-lysine and 48.2 g·L^-15-AVA were obtained with yield of 47.4%and 42.3%,respectively,by the microbial racemization and asymmetric degradation process.The final D-lysine enantiomeric excess was over 99%.Meanwhile,a valuable compound 5-aminovaleric acid was synthesized with the production of D-lysine,indicating the economic feasibility of the two-strain coupling system.
基金supported by the fund of Doctor Startup Project in Anhui Academy of Agricultural Sciences of Chinathe Project of Anhui Poultry Technology Committee, China (AHCYTX-10)
文摘A total of 900 one-d-old Chinese Huainan Partridge Shank chickens were randomly allocated into nine groups with five replicates of 20 each.Birds were fed with basal diet,basal diet supplemented with 150 mg kg^（–1） aureomycin,basal diet supplemented with different proportions of Bacillus licheniformis and Bacillus subtilis,which was 0：1.0×10~6,2.5×10~5：7.5×10~5,3.3×10~5：6.6×10~5,5.0×10~5：5.0×10~5,6.6×10~5：3.3×10~5,7.5×10~5：2.5×10~5 and 1.0×10~6：0,respectively.The duration of the experiment was 56 d.The results indicated that dietary supplementation of 6.6×10~5：3.3×10~5 of B.lichenifornis：B.subtilis improved final body weight,increased the average daily gain,and reduced feed/gain ratio（P〈0.05）.The numbers of total Lactobacillus and Bifidobacterium sp.in the caecum significantly increased,and the numbers of Escherichia coli and Salmonella sp.significantly declined compared to that of the control（P〈0.05）.Intestinal villous height and villous height to crypt depth ratio of the duodenum,jejunum,and ileum were significantly higher than that of the control,and intestinal crypt depth of the duodenum and ileum was significantly lower（P〈0.05）.The total antioxidant capacity,total superoxide dismutase,and glutathione peroxidase ability in plasma significantly improved,while the malondialdehyde concentration in plasma decreased（P〈0.05）.Compared to the control,plasma concentrations of ammonia,uric acid and urea nitrogen and the activity of xanthine oxidase were reduced（P〈0.05）.In conclusion,an inclusion of 6.6×10~5：3.3×10~5 of B.licheniformis：B.subtilis to the diet improved the growth performance,caecal microbiota,plasma biochemical profile,and significantly improved the small intestine morphology,while reducing the mortality rate.
基金This research was partially supported by the National Natural Science Foundation of China(Nos.12071115,11871179)the Heilongjiang Natural Science Funds for Distinguished Young Scholar(No.JQ2023A005),and Heilongjiang Provincial Key Laboratory of the Theory and Computation of Complex Systems(JW)NSERC of Canada(No.RGPIN-2019-05892)(YC).
文摘We propose a malaria model involving the sensitive and resistant strains,which is described by reaction-diffusion equations.The model reflects the scenario that the vector and host populations disperse with distinct diffusion rates,susceptible individuals or vectors cannot be infected by both strains simultaneously,and the vector population satisfies the logistic growth.Our main purpose is to get a threshold type result on the model,especially the interaction effect of the two strains in the presence of spatial structure.To solve this issue,the basic reproduction number(BRN)R_(0)^(i)and invasion reproduction number(IRN)R_(0)^(i)of each strain(i=1 and 2 are for the sensitive and resistant strains,respectively)are defined.Furthermore,we investigate the influence of the diffusion rates of populations and vectors on BRNs and IRNs.
基金supported by Grant-in-Aid for Scientific Research from JSPS,Japan,KAKENHI(Grant No.JP 19KK0262,JP 20H02314,JP 20K21062)a warded to Professor Tanimoto.
文摘The emergence of a novel strain during a pandemic,like the current COVID-19,is a major concern to the healthcare system.The most effective strategy to control this type of pandemic is vaccination.Many previous studies suggest that the existing vaccine may not be fully effective against the new strain.Additionally,the new strain's late arrival has a significant impact on the disease dynamics and vaccine coverage.Focusing on these issues,this study presents a two-strain epidemic model in which the new strain appears with a time delay.We considered two vaccination provisions,namely preinfection and post-infection vaccinations,which are governed by human behavioral dynamics.In such a framework,individuals have the option to commit vaccination before being infected with the first strain.Additionally,people who forgo vaccination and become infected with the first train have the chance to be vaccinated(after recovery)in an attempt to avoid infection from the second strain.However,a second strain can infect vaccinated and unvaccinated individuals.People may have additional opportunities to be vaccinated and to protect themselves from the second strain due to the time delay.Considering the cost of the vaccine,the severity of the new strain,and the vaccine's effectiveness,our results indicated that delaying the second strain decreases the peak size of the infected individuals.Finally,by estimating the social efficiency deficit,we discovered that the social dilemma for receiving immunization decreases with the delay in the arrival of the second strain.
文摘Background： Human immunodeficiency virus isolates most often use chemokine receptor CCR5 or CXCR4 as a coreceptor to enter target cells. During early stages of HIV-1 infection, CCR5-tropic viruses are the predominant species. The CXCR4-tropic viruses may emerge late in infection. Recognition of factors influencing this phenotypic switch may give some hints on the antiviral strategies like anti-H1V/AIDS drugs, gene therapy and vaccines. Methods： To investigate the mechanism that triggers R5 to X4 phenotypic switch, we performed a systematic sensitivity analysis based on a five-dimensional model with time-varying parameters. We studied the sensitivity of each factor to the CCR5-to-CXCR4 tropism switch and acquired some interesting outcomes beyond expectation. Results： The death rate of free virus （dv）, rate that uninfected CD4＋ T cells arise from precursors （s） and proliferate as stimulated by antigens （r）, and in vivo viral burst size （N） are four robust factors which are constantly observed to have a strong correlation with the evolution of viral phenotype for most patients longitudinally. Conclusions： Crucial factors, which are essential to phenotypie switch and disease progression, are almost the same for different patients at different time points, including the production of both virus and CD4＋ T cells and the decay of virion. It is also worth mentioning that although the sequence of factors sorted by the influence varies between patients, the trends of influences engendered by most factors as disease progresses are similar inter-patients.
文摘In this paper, we propose a two strain epidemic model with single host population. It is assumed that strain one can mutate into strain two. Also latent-stage progression age and mutation are incorporated into the model. Stability of equilibria （including the disease free equilibrium, dominant equilibria and the coexistence equilibrium） is investigated and it is found that they are locally stable under suitable and biological feasible constraints. Results indicate that the competition exclusion and coexistence of the two strains are possible depending on the mutation. Numerical simulations are also performed to illustrate these results.
