Disclosed is a modified microorganism producing putrescine or ornithine, and a method for producing putrescine or ornithine using the same.

The invention relates to a method for the protein enrichment of a heterotrophically cultured microalga, the microalga being of the genus Chlorella, even more particularly Chlorella protothecoides, characterized in that it comprises: a first step directed toward limiting the ammonium supply so as to obtain a microalgal biomass with a protein content of less than 50% expressed as N.6.25, preferably less than 30%, more preferentially between 20 and 25%; a second step in which the ammonium supply in the fermentation medium is increased so as to obtain a protein content of greater than 50%, preferably greater than 60%, more preferentially greater than 65%.

The invention relates to a method for the protein enrichment of a heterotrophically cultured microalga, the microalga being of the genus Chlorella, even more particularly Chlorella protothecoides, characterized in that it comprises: a first step directed toward limiting the ammonium supply so as to obtain a microalgal biomass with a protein content of less than 50% expressed as N.6.25, preferably less than 30%, more preferentially between 20 and 25%; a second step in which the ammonium supply in the fermentation medium is increased so as to obtain a protein content of greater than 50%, preferably greater than 60%, more preferentially greater than 65%.

A method for producing an L-amino acid such as L-glutamic acid is provided. An L-amino acid is produced by culturing in a culture medium a bacterium belonging to the family Enterobacteriaceae and having an L-amino acid-producing ability, and collecting the L-amino acid from the culture medium and/or cells of the bacterium, wherein the bacterium has been modified to have one or more of the following modifications: (A) modification of reducing the activity of a BudA protein; (B) modification of reducing the activity of a BudB protein; (C) modification of reducing the activity of a BudC protein; (D) modification of reducing the activity of a PAJ_3461 protein; (E) modification of reducing the activity of a PAJ_3462 protein; and (F) modification of reducing the activity of a PAJ_3463 protein.

The invention discloses a method for increasing the yield of L-arginine by knocking out flavin reductases, and belongs to the technical field of amino acid production by microbial fermentation. Genes frd1 and frd2 for encoding hypothetic NADPH-dependent FMN reductase in Corynebacterium crenatum SDNN403 are over-expressed in E. coli BL21 and are purified to form target proteins Frd181 and Frd188, and functions of the target proteins are identified to obtain a result showing that the proteins Frd181 and Frd188 both are NAD(P)H-dependent flavin reductases producing H.sub.2O.sub.2. By taking a genome of the Corynebacterium crenatum SDNN403 as a template, frd1 and frd2 gene deletion fragments are obtained by overlap extension PCR; connecting pK18mobsacB to obtain knockout plasmids pK18mobsacB-frd1 and pK18mobsacB-frd2; carrying out electric shock to transform the Corynebacterium crenatum SDNN403; and carrying out secondary screening to obtain recombinant strains 403frd1 and 403frd2. Found by flask shaking fermentation, the yield of L-arginine is obviously increased by knocking out the genes frd1 and frd2.

The invention discloses a method for increasing the yield of L-arginine by knocking out flavin reductases, and belongs to the technical field of amino acid production by microbial fermentation. Genes frd1 and frd2 for encoding hypothetic NADPH-dependent FMN reductase in Corynebacterium crenatum SDNN403 are over-expressed in E. coli BL21 and are purified to form target proteins Frd181 and Frd188, and functions of the target proteins are identified to obtain a result showing that the proteins Frd181 and Frd188 both are NAD(P)H-dependent flavin reductases producing H.sub.2O.sub.2. By taking a genome of the Corynebacterium crenatum SDNN403 as a template, frd1 and frd2 gene deletion fragments are obtained by overlap extension PCR; connecting pK18mobsacB to obtain knockout plasmids pK18mobsacB-frd1 and pK18mobsacB-frd2; carrying out electric shock to transform the Corynebacterium crenatum SDNN403; and carrying out secondary screening to obtain recombinant strains 403frd1 and 403frd2. Found by flask shaking fermentation, the yield of L-arginine is obviously increased by knocking out the genes frd1 and frd2.

The invention relates to therapeutic applications for compositions that reduce the level of oxidative stress on cells in vivo or in vitro. The invention describes methods for improving the therapeutic properties of stem cells. The invention also provides combination therapies that are useful to balance the oxidative microenvironment of cells in vivo or in vitro.

The present invention provides a method for producing L-amino acids by fermentation using a bacterium belonging to the family Enterobacteriaceae which has been modified to overexpress a gene encoding an iron exporter, such as a fetB gene, fetA gene, fieF gene, or a combination of these genes.

The present invention provides a method for producing L-amino acids by fermentation using a bacterium belonging to the family Enterobacteriaceae which has been modified to overexpress a gene encoding an iron exporter, such as a fetB gene, fetA gene, fieF gene, or a combination of these genes.

The present invention relates to a Corynebacterium glutamicum mutant strain having increased L-citrulline productivity, and a method of producing L-citrulline using the same. The Corynebacterium glutamicum mutant strain is capable of producing L-citrulline in high yield and high concentration while inhibiting the production of by-products, because the activity of the protein that is expressed by the NCgl2657 gene therein has been weakened or inactivated.