The relatively low sensitivity is an important reason for restricting the microbial fuel cell(MFC)sensors'application in low concentration biodegradable organic matter(BOM)detection.The startup parameters,includin...The relatively low sensitivity is an important reason for restricting the microbial fuel cell(MFC)sensors'application in low concentration biodegradable organic matter(BOM)detection.The startup parameters,including substrate concentration,anode area and external resistance,were regulated to enhance the sensitivity of MFC sensors.The results demonstrated that both the substrate concentration and anode area were positively correlated with the sensitivity of MFC sensors,and an external resistance of 210Ωwas found to be optimal in terms of sensitivity of MFC sensors.Optimized MFC sensors had lower detection limit(1 mg/L)and higher sensitivity(Slope value of the linear regression curve was 1.02),which effectively overcome the limitation of low concentration BOM detection.The essential reason is that optimized MFC sensors had higher coulombic efficiency,which was beneficial to improve the sensitivity of MFC sensors.The main impact of the substrate concentration and anode area was to regulate the proportion between electrogens and nonelectrogens,biomass and living cells of the anode biofilm.The external resistance mainly affected the morphology structure and the proportion of living cells of the anode.This study demonstrated an effective way to improve the sensitivity of MFC sensors for low concentration BOM detection.展开更多
In gene regulatory networks, gene regulation loops often occur with multiple positive feedback, multiple negative feedback and coupled positive and negative feedback forms. In above gene regulation loops, auto-activat...In gene regulatory networks, gene regulation loops often occur with multiple positive feedback, multiple negative feedback and coupled positive and negative feedback forms. In above gene regulation loops, auto-activation loops are ubiquitous regulatory motifs. This paper aims to investigate a two-component dual-positive feedback genetic circuit, which consists of a double negative feedback circuit and an additional positive feedback loop(APFL). We study effect of substrate concentration on gene expression in the single and the networked systems with APFLs, respectively. We find that substrate concentration can tune stochastic switch behavior in the signal system and then we explore relationship of substrate concentration with positive feedback strength in aspect of stochastic switch behavior. Furthermore, we also discuss gene expression and stochastic switch behavior in the networked systems with APFLs. Based on analysis in the networked systems, we discover that genes express in some specific cells and do not express in the other cells when the expression achieves its steady state. These results can be used to well explain the character of regionalization in the expression of genes and the phenomenon of gene differentiation.展开更多
The effects of initial substrate (5-60 g /L) and biomass concentration (0.5-3 g /L) on fermentative hydrogen production by mixed cultures were investigated in batch tests using glucose as substrate.The experimental re...The effects of initial substrate (5-60 g /L) and biomass concentration (0.5-3 g /L) on fermentative hydrogen production by mixed cultures were investigated in batch tests using glucose as substrate.The experimental results showed that the hydrogen production increases as the initial substrate concentration increases from 0 to 25 g /L.It indicated that the shift in the metabolic pathway or in the composition of the bacterial flora occurs.The maximum hydrogen yield of 1.78 mol /mol-glucose is obtained at the substrate concentration of 15 g /L.This study also shows that initial biomass concentration affects the hydrogen yield as the cumulative hydrogen production has been increased with the increase of initial cell concentration up to 1.5 g /L and reached the highest level.The maximum hydrogen yield is obtained at the cell concentration of 1.5 g /L.It indicated that the optimum biomass /substrate ratio,maximizing the hydrogen yield and the hydrogen production rate,is determined to be 0.1 g biomass /g glucose.展开更多
Improving substrate utilization is crucial for industrial conversion of starch.The introduction of pullulanase in cyclodextrin(CD)production has improved substrate utilization.However,complete utilization of debranche...Improving substrate utilization is crucial for industrial conversion of starch.The introduction of pullulanase in cyclodextrin(CD)production has improved substrate utilization.However,complete utilization of debranched starches has not been achieved,mainly due to the retrogradation of debranched starches and the inhibitory effect of CDs on pullulanase during the catalytic reaction.This study aimed to establish an efficient CD preparation system by regulating the substrate concentration and reaction temperature.A Bacillus thermoleovorans pul-lulanase(BtPul)was selected for investigation of its interaction with CDs through inhibition pattern assays,fluorescence spectroscopy,and molecular docking.Results clarified that CDs inhibited BtPul,withα-CD showing the highest inhibition,followed by β-CD and γ-CD.γ-CD inhibited BtPul through a mixed mode of competitive and noncompetitive inhibition,while the other CDs inhibited BtPul competitively.When pullulan was used as the substrate,increasing the substrate concentration weakened the inhibitory effect of CDs to some degree,while changes in reaction temperature only had a minor contribution.When BtPul and β-CGTase collaboratively converted 30%(w/v)starch substrate,an increase in reaction temperature improved the conversion rate of β-CD from 67.6%to 86.8%.Optimization of substrate concentration showed that high concentration starch substrate had an adverse effect on CDs yield due to retrogradation.The optimal yields of α-CD and β-CD produced by BtPul and α-/β-CGTases were 55.7%and 90.3%,respectively.This study provides a reliable method and reference for the efficient conversion of starch into CDs.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51525805,51727812 and 51808527)the Soft Science Research Project of Sichuan(No.2019JDR0286)the Special Research Assistant Program of Chinese Academy of Science。
文摘The relatively low sensitivity is an important reason for restricting the microbial fuel cell(MFC)sensors'application in low concentration biodegradable organic matter(BOM)detection.The startup parameters,including substrate concentration,anode area and external resistance,were regulated to enhance the sensitivity of MFC sensors.The results demonstrated that both the substrate concentration and anode area were positively correlated with the sensitivity of MFC sensors,and an external resistance of 210Ωwas found to be optimal in terms of sensitivity of MFC sensors.Optimized MFC sensors had lower detection limit(1 mg/L)and higher sensitivity(Slope value of the linear regression curve was 1.02),which effectively overcome the limitation of low concentration BOM detection.The essential reason is that optimized MFC sensors had higher coulombic efficiency,which was beneficial to improve the sensitivity of MFC sensors.The main impact of the substrate concentration and anode area was to regulate the proportion between electrogens and nonelectrogens,biomass and living cells of the anode biofilm.The external resistance mainly affected the morphology structure and the proportion of living cells of the anode.This study demonstrated an effective way to improve the sensitivity of MFC sensors for low concentration BOM detection.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFB0800401)the National Natural Science Foundation of China(Grant Nos.61773153,61621003,61532020,11472290,and 61472027)
文摘In gene regulatory networks, gene regulation loops often occur with multiple positive feedback, multiple negative feedback and coupled positive and negative feedback forms. In above gene regulation loops, auto-activation loops are ubiquitous regulatory motifs. This paper aims to investigate a two-component dual-positive feedback genetic circuit, which consists of a double negative feedback circuit and an additional positive feedback loop(APFL). We study effect of substrate concentration on gene expression in the single and the networked systems with APFLs, respectively. We find that substrate concentration can tune stochastic switch behavior in the signal system and then we explore relationship of substrate concentration with positive feedback strength in aspect of stochastic switch behavior. Furthermore, we also discuss gene expression and stochastic switch behavior in the networked systems with APFLs. Based on analysis in the networked systems, we discover that genes express in some specific cells and do not express in the other cells when the expression achieves its steady state. These results can be used to well explain the character of regionalization in the expression of genes and the phenomenon of gene differentiation.
基金Sponsored by the State Key Laboratory of Urban Water Resource and Environment of Harbin Institute of Technology(Grant No.2010DX06)the National High Technology Research and Development Program of China(Grant No.2006AA05Z109)the Harbin Science and Technology Bureau(Grant No.2009RFXXS004)
文摘The effects of initial substrate (5-60 g /L) and biomass concentration (0.5-3 g /L) on fermentative hydrogen production by mixed cultures were investigated in batch tests using glucose as substrate.The experimental results showed that the hydrogen production increases as the initial substrate concentration increases from 0 to 25 g /L.It indicated that the shift in the metabolic pathway or in the composition of the bacterial flora occurs.The maximum hydrogen yield of 1.78 mol /mol-glucose is obtained at the substrate concentration of 15 g /L.This study also shows that initial biomass concentration affects the hydrogen yield as the cumulative hydrogen production has been increased with the increase of initial cell concentration up to 1.5 g /L and reached the highest level.The maximum hydrogen yield is obtained at the cell concentration of 1.5 g /L.It indicated that the optimum biomass /substrate ratio,maximizing the hydrogen yield and the hydrogen production rate,is determined to be 0.1 g biomass /g glucose.
基金supported by Natural Science Foundation of Jiangsu Province(BK20221072)National Natural Science Foundation of China(No.32201967)National Key Research and Development Program of China(2023YFF1103600).
文摘Improving substrate utilization is crucial for industrial conversion of starch.The introduction of pullulanase in cyclodextrin(CD)production has improved substrate utilization.However,complete utilization of debranched starches has not been achieved,mainly due to the retrogradation of debranched starches and the inhibitory effect of CDs on pullulanase during the catalytic reaction.This study aimed to establish an efficient CD preparation system by regulating the substrate concentration and reaction temperature.A Bacillus thermoleovorans pul-lulanase(BtPul)was selected for investigation of its interaction with CDs through inhibition pattern assays,fluorescence spectroscopy,and molecular docking.Results clarified that CDs inhibited BtPul,withα-CD showing the highest inhibition,followed by β-CD and γ-CD.γ-CD inhibited BtPul through a mixed mode of competitive and noncompetitive inhibition,while the other CDs inhibited BtPul competitively.When pullulan was used as the substrate,increasing the substrate concentration weakened the inhibitory effect of CDs to some degree,while changes in reaction temperature only had a minor contribution.When BtPul and β-CGTase collaboratively converted 30%(w/v)starch substrate,an increase in reaction temperature improved the conversion rate of β-CD from 67.6%to 86.8%.Optimization of substrate concentration showed that high concentration starch substrate had an adverse effect on CDs yield due to retrogradation.The optimal yields of α-CD and β-CD produced by BtPul and α-/β-CGTases were 55.7%and 90.3%,respectively.This study provides a reliable method and reference for the efficient conversion of starch into CDs.
