Clostridium acetobutylicum has been extensively exploited to produce biofuels and solvents and its biofilm could dramatically improve the productivities.However,genetic control of C.acetobutylicum biofilm has not been...Clostridium acetobutylicum has been extensively exploited to produce biofuels and solvents and its biofilm could dramatically improve the productivities.However,genetic control of C.acetobutylicum biofilm has not been dissected so far.Here,to identify potential genes controlling C.acetobutylicum biofilm formation,over 40 gene candidates associated with extracellular matrix,cell surface,cell signaling or gene transcription,were tried to be disrupted to examine their individual impact.A total of 25 disruptants were finally obtained over years of attempts,for which biofilm and relevant phenotypes were characterized.Most of these disruptants formed robust biofilm still,or suffered both growth and biofilm defect.Only a strain with a disrupted histidine kinase gene(CA_C2730,designated bfcK in this study)abolished biofilm formation without impairing cell growth or solvent production.Further analysis revealed that bfcK could control flagellar biogenesis and cell motility at protein levels.The bfcK also appeared to repress the phosphorylation of a serine/threonine protein kinase(encoded by CA_C0404)that might negatively regulate biofilm formation.Based on these findings,possible bfcK-mediated mechanisms for biofilm formation were proposed.This is a big step toward understanding the biofilm formation in C.acetobutylicum and will help further engineering of its biofilm-based industrial processes.展开更多
Acetone–butanol–ethanol(ABE)fermentation process can be exploited for the generation of butanol as biofuel,however it does need to overcome its low volumetric solvent productivity before it can commercially compete ...Acetone–butanol–ethanol(ABE)fermentation process can be exploited for the generation of butanol as biofuel,however it does need to overcome its low volumetric solvent productivity before it can commercially compete with fossil fuel technologies.In this regard,mathematical modelling and simulation analysis are tools that can serve as the base for process engineering development of biological systems.In this work,a novel phenomenological kinetic model of Clostridium acetobutylicum ATCC 824 was considered as a benchmark system to evaluate the behaviour of an ABE fermentation under different process configurations using both free and immobilized cells:single stage batch operation,fed-batch,single stage Continuous Stirred Tank Reactor(CSTR)and multistage CSTRs with and without biomass recirculation.The proposed model achieved a linear correlation index r^2=0.9952 and r^2=0.9710 over experimental data for free and immobilized cells respectively.The predicted maximum butanol concentration and productivity obtained were 13.08 g·L^(-1)and 1.9620 g·L^(-1)·h^(-1)respectively,which represents an increase of 1.01%and 990%versus the currently developed industrial scale process reported currently into the literature.These results provide a reliable platform for the design and optimization of the ABE fermentation system and showcase the adequate predictive nature of the proposed model.展开更多
There has been a surge of interest in acetone-butanol-ethanol fermentations of Clostridium acetobutylicum due to its capacity to ferment many carbohydrates found in biomass. This metabolic diversity makes it a promisi...There has been a surge of interest in acetone-butanol-ethanol fermentations of Clostridium acetobutylicum due to its capacity to ferment many carbohydrates found in biomass. This metabolic diversity makes it a promising candidate for conversion of inexpensive, heterogeneous carbohydrate feedstocks to biofuels. Galactose is present in many such feedstocks due to its incorporation in plant cell walls. C. acetobutylicum encodes two galactose utilization pathways, the Leloir (LP) and the tagatose-6-P (T6P), and a previous study indicated genes for these pathways was differentially regulated during growth on galactose and lactose. In the current study we utilized quantitative PCR to further investigate gene expression levels and to show both pathways which were subject to carbon catabolite repression. During growth on galactose, mRNA for galactose-6-P isomerase from the T6P was induced to a greater extent than mRNA for glactokinase, the first enzyme in the LP. The galactose-6-P isomerase mRNAs were also more abundant than galactokinase mRNAs during growth on galactose. Analysis of theoretical ATP requirements to generate essential precursor metabolites indicated: 1) the LP is more efficient at generating upper glycolytic intermediates, 2) the T6P is more efficient at forming ATP, lower glycolytic intermediates and TCA cycle intermediates, 3) a combination of the two pathways is most efficient for forming precursor metabolites found in the pentose phosphate pathway. From this it can be suggested that the two pathways have different roles in the organism with the T6P generating most ATP and precursor metabolites and the LP providing upper glycolytic metabolites.展开更多
基金This work was supported by the Key Program of the National Natural Science Foundation of China(Grant No.21636003)the Outstanding Youth Foundation of Jiangsu(Grant No.SBK2017010373)+1 种基金the National Key Research and Development Program of China(Grant No.2019YFD1101204)the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture.Dong Liu is supported by the Jiangsu Qinglan Talent Program.
文摘Clostridium acetobutylicum has been extensively exploited to produce biofuels and solvents and its biofilm could dramatically improve the productivities.However,genetic control of C.acetobutylicum biofilm has not been dissected so far.Here,to identify potential genes controlling C.acetobutylicum biofilm formation,over 40 gene candidates associated with extracellular matrix,cell surface,cell signaling or gene transcription,were tried to be disrupted to examine their individual impact.A total of 25 disruptants were finally obtained over years of attempts,for which biofilm and relevant phenotypes were characterized.Most of these disruptants formed robust biofilm still,or suffered both growth and biofilm defect.Only a strain with a disrupted histidine kinase gene(CA_C2730,designated bfcK in this study)abolished biofilm formation without impairing cell growth or solvent production.Further analysis revealed that bfcK could control flagellar biogenesis and cell motility at protein levels.The bfcK also appeared to repress the phosphorylation of a serine/threonine protein kinase(encoded by CA_C0404)that might negatively regulate biofilm formation.Based on these findings,possible bfcK-mediated mechanisms for biofilm formation were proposed.This is a big step toward understanding the biofilm formation in C.acetobutylicum and will help further engineering of its biofilm-based industrial processes.
基金financial support via the postgraduate scholarship No.277760
文摘Acetone–butanol–ethanol(ABE)fermentation process can be exploited for the generation of butanol as biofuel,however it does need to overcome its low volumetric solvent productivity before it can commercially compete with fossil fuel technologies.In this regard,mathematical modelling and simulation analysis are tools that can serve as the base for process engineering development of biological systems.In this work,a novel phenomenological kinetic model of Clostridium acetobutylicum ATCC 824 was considered as a benchmark system to evaluate the behaviour of an ABE fermentation under different process configurations using both free and immobilized cells:single stage batch operation,fed-batch,single stage Continuous Stirred Tank Reactor(CSTR)and multistage CSTRs with and without biomass recirculation.The proposed model achieved a linear correlation index r^2=0.9952 and r^2=0.9710 over experimental data for free and immobilized cells respectively.The predicted maximum butanol concentration and productivity obtained were 13.08 g·L^(-1)and 1.9620 g·L^(-1)·h^(-1)respectively,which represents an increase of 1.01%and 990%versus the currently developed industrial scale process reported currently into the literature.These results provide a reliable platform for the design and optimization of the ABE fermentation system and showcase the adequate predictive nature of the proposed model.
文摘There has been a surge of interest in acetone-butanol-ethanol fermentations of Clostridium acetobutylicum due to its capacity to ferment many carbohydrates found in biomass. This metabolic diversity makes it a promising candidate for conversion of inexpensive, heterogeneous carbohydrate feedstocks to biofuels. Galactose is present in many such feedstocks due to its incorporation in plant cell walls. C. acetobutylicum encodes two galactose utilization pathways, the Leloir (LP) and the tagatose-6-P (T6P), and a previous study indicated genes for these pathways was differentially regulated during growth on galactose and lactose. In the current study we utilized quantitative PCR to further investigate gene expression levels and to show both pathways which were subject to carbon catabolite repression. During growth on galactose, mRNA for galactose-6-P isomerase from the T6P was induced to a greater extent than mRNA for glactokinase, the first enzyme in the LP. The galactose-6-P isomerase mRNAs were also more abundant than galactokinase mRNAs during growth on galactose. Analysis of theoretical ATP requirements to generate essential precursor metabolites indicated: 1) the LP is more efficient at generating upper glycolytic intermediates, 2) the T6P is more efficient at forming ATP, lower glycolytic intermediates and TCA cycle intermediates, 3) a combination of the two pathways is most efficient for forming precursor metabolites found in the pentose phosphate pathway. From this it can be suggested that the two pathways have different roles in the organism with the T6P generating most ATP and precursor metabolites and the LP providing upper glycolytic metabolites.
