Riboflavin,an important vitamin utilized in pharmaceutical products and as a feed additive,is mainly produced by metabolically engineered bacterial fermentation.However,the reliance on antibiotics in the production pr...Riboflavin,an important vitamin utilized in pharmaceutical products and as a feed additive,is mainly produced by metabolically engineered bacterial fermentation.However,the reliance on antibiotics in the production process leads to increased costs and safety risks.To address these challenges,an antibiotic-free Escherichia coli riboflavin producer was constructed using metabolic engineering approaches coupled with a novel plasmid stabilization system.Initially,competitive pathways and feedback inhibition were attenuated to enhance the metabolic flux towards riboflavin.Key genes in the purine pathway were overexpressed to boost the availability of riboflavin precursors.Subsequently,a plasmid stabilization system based on toxin was screened and characterized,achieving a plasmid retention rate of 84.9%after 10 days of passaging.Finally,transcriptomic analysis at the genome-wide level revealed several rate-limiting genes,including pgl,gnd,and yigB,which were subsequently upregulated,leading to a 26%improvement in riboflavin production.With optimization of the culture medium,the final strain allowed the production of 11.5 g/L of riboflavin with a yield of 90.4 mg/g glucose in 5 L bioreactors without antibiotics.These strategies can be extended to other plasmid-based riboflavin derivative production systems.展开更多
This paper proposes an adaptive integrated hybrid AC/DC microgrid module to accommodate a wide range of distributed renewable energy resources(DRERs),distributed energy storage devices(DESDs)and distributed demand res...This paper proposes an adaptive integrated hybrid AC/DC microgrid module to accommodate a wide range of distributed renewable energy resources(DRERs),distributed energy storage devices(DESDs)and distributed demand resources(DDRs)into the existing distribution systems.This microgrid module is designed to be portable,scalable,easy to deploy,and simple to operate.The modeling of the proposed microgrid module,based on the IEC 61850 standard,is presented.A novel logical node is introduced,which describes functionalities of the bidirectional interlinking converter(BIC)interfacing AC sub-grid and DC sub-grid in a better way.To achieve the target of plug-and-play functionalities,specific microgrid module communication network(MMCN)and microgrid module operating systems(MMOS)are designed and implemented in the hardware prototype built in the laboratory.Experimental results obtained from the lab prototype clearly validate the effectiveness of the proposed design of the microgrid module,communication network and operating system.展开更多
5-Aminolevulinic acid(5-ALA)serves as a key precursor for tetrapyrrole compounds biosynthesis.Conventional high-producing strains often rely on multi-copy plasmids,causing instability and elevated costs.In this study,...5-Aminolevulinic acid(5-ALA)serves as a key precursor for tetrapyrrole compounds biosynthesis.Conventional high-producing strains often rely on multi-copy plasmids,causing instability and elevated costs.In this study,a plasmid-free,inducer-free,and antibiotic-free 5-ALA cell factory was constructed via chromosomal integration to improve strain robustness and scalability.Using DLKcat-based computational screening,an efficient 5-aminolevu-linate synthase(ALAS)derived from Methylocystis sp.was identified,achieving a 5-ALA titer of 3.60 g/L in shake flasks.Subsequently,promoter library-based tuning of the downstream gene hemB increased the titer by 15.83%.Further rational engineering of key metabolic targets increased the titer to 7.14 g/L.Transcriptomic analysis enabled the identification and introduction of transcription factor PspC,yielding strain ALA33 with 8.04 g/L 5-ALA.Without the addition of exogenous antibiotics or inducers,ALA33 achieved a 5-ALA titer of 40.88 g/L through fed-batch fermentation,showing a practical strategy for stable and efficient industrial production of 5-ALA and tetrapyrroles.展开更多
基金supported by the National Key Research and Devel-opment Program of China(No.2021YFC2100900,2022YFA0912200)the National Natural Science Foundation of China(No.32071470,32300063)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20221080,No.BK20210464)the Research Program of State Key Laboratory of Food Science and Resources,Jiangnan University(No.SKLF-ZZB-202408).
文摘Riboflavin,an important vitamin utilized in pharmaceutical products and as a feed additive,is mainly produced by metabolically engineered bacterial fermentation.However,the reliance on antibiotics in the production process leads to increased costs and safety risks.To address these challenges,an antibiotic-free Escherichia coli riboflavin producer was constructed using metabolic engineering approaches coupled with a novel plasmid stabilization system.Initially,competitive pathways and feedback inhibition were attenuated to enhance the metabolic flux towards riboflavin.Key genes in the purine pathway were overexpressed to boost the availability of riboflavin precursors.Subsequently,a plasmid stabilization system based on toxin was screened and characterized,achieving a plasmid retention rate of 84.9%after 10 days of passaging.Finally,transcriptomic analysis at the genome-wide level revealed several rate-limiting genes,including pgl,gnd,and yigB,which were subsequently upregulated,leading to a 26%improvement in riboflavin production.With optimization of the culture medium,the final strain allowed the production of 11.5 g/L of riboflavin with a yield of 90.4 mg/g glucose in 5 L bioreactors without antibiotics.These strategies can be extended to other plasmid-based riboflavin derivative production systems.
文摘This paper proposes an adaptive integrated hybrid AC/DC microgrid module to accommodate a wide range of distributed renewable energy resources(DRERs),distributed energy storage devices(DESDs)and distributed demand resources(DDRs)into the existing distribution systems.This microgrid module is designed to be portable,scalable,easy to deploy,and simple to operate.The modeling of the proposed microgrid module,based on the IEC 61850 standard,is presented.A novel logical node is introduced,which describes functionalities of the bidirectional interlinking converter(BIC)interfacing AC sub-grid and DC sub-grid in a better way.To achieve the target of plug-and-play functionalities,specific microgrid module communication network(MMCN)and microgrid module operating systems(MMOS)are designed and implemented in the hardware prototype built in the laboratory.Experimental results obtained from the lab prototype clearly validate the effectiveness of the proposed design of the microgrid module,communication network and operating system.
基金supported by the National Key Research and Development Program of China(2023YFA0914500)the National Natural Science Foundation of China(32470067,32370040)+2 种基金the Jiangsu Provincial Frontier Technology Research and Development Program(BF2024012)the Basic Research Program of Jiangsu(BK20233003)the Fundamental Research Funds for the Central Universities(JUSRP124018).
文摘5-Aminolevulinic acid(5-ALA)serves as a key precursor for tetrapyrrole compounds biosynthesis.Conventional high-producing strains often rely on multi-copy plasmids,causing instability and elevated costs.In this study,a plasmid-free,inducer-free,and antibiotic-free 5-ALA cell factory was constructed via chromosomal integration to improve strain robustness and scalability.Using DLKcat-based computational screening,an efficient 5-aminolevu-linate synthase(ALAS)derived from Methylocystis sp.was identified,achieving a 5-ALA titer of 3.60 g/L in shake flasks.Subsequently,promoter library-based tuning of the downstream gene hemB increased the titer by 15.83%.Further rational engineering of key metabolic targets increased the titer to 7.14 g/L.Transcriptomic analysis enabled the identification and introduction of transcription factor PspC,yielding strain ALA33 with 8.04 g/L 5-ALA.Without the addition of exogenous antibiotics or inducers,ALA33 achieved a 5-ALA titer of 40.88 g/L through fed-batch fermentation,showing a practical strategy for stable and efficient industrial production of 5-ALA and tetrapyrroles.
