The invention discloses a method for improving the yield of Bacillus subtilis acetylglucosamine, which belongs to the technical field of genetic engineering. In the invention, the recombinant Bacillus subtilis S5 (S5-PxylA-glmS-P43-GNA1) is taken as a starting strain, and the glmS ribozyme is integrated into the mid of rbs and the promoter sequence of the glmM and pfkA gene, respectively. The ribozyme mutant has the advantage of prolonging the stability of the mRNA and integrated into the mid of rbs and the promoter sequence of the pgi gene. The yield of GlcNAc of the recombinant strain reaches 11.79-20.05 g/L. This laid the foundation for the further metabolic engineering of Bacillus subtilis to produce GlcNAc.

An isolated nucleic acid molecule is provided comprising a nucleotide sequence which encodes a glutamine:fructose-6-phosphate amidotransferase from E. coli which is particularly suitable for expression in cotton plant cells. The invention also relates to plant cells or plants, in particular to cotton plant cells or cotton plants which produce an increased amount of positively charged polysaccharides in their cell walls. Furthermore, methods and means are provided to increase the content of positively charged polysaccharides in the cell walls of cotton cells, in particular in cotton fibers. Fibers obtained from such cotton plants have an altered chemical reactivity which can be used to attach reactive dyes or other textile finish reagents to these fibers.

The present invention discloses a directionally modified glucosamine synthase mutant and its application. The amino acid sequence of the glucosamine synthase mutant is as shown in sequence list SEQ ID No. 1, and the nucleotide sequence is as shown in sequence list SEQ ID No. 2. The genetic engineering bacteria of glucosamine synthase is successfully constructed. In order to improve the tolerance of recombinant bacteria against glucosamine, the glucosamine synthase is directionally modified. A glucosamine synthase mutant is selected from the mutant library via high-throughput screening method, the amino acid changes in the mutant induces the spatial conformational change in the enzyme, so as enlarged the region where the enzyme and substrate combines, therefor the combination efficiency of the enzyme and the substrate is increased. The glucosamine synthase of the present invention has various advantages, such as rich in raw material of glucose, and a convenient subsequent extraction.

The present invention discloses a directionally modified glucosamine synthase mutant and its application. The amino acid sequence of the glucosamine synthase mutant is as shown in sequence list SEQ ID No. 1, and the nucleotide sequence is as shown in sequence list SEQ ID No. 2. The genetic engineering bacteria of glucosamine synthase is successfully constructed. In order to improve the tolerance of recombinant bacteria against glucosamine, the glucosamine synthase is directionally modified. A glucosamine synthase mutant is selected from the mutant library via high-throughput screening method, the amino acid changes in the mutant induces the spatial conformational change in the enzyme, so as enlarged the region where the enzyme and substrate combines, therefor the combination efficiency of the enzyme and the substrate is increased. The glucosamine synthase of the present invention has various advantages, such as rich in raw material of glucose, and a convenient subsequent extraction.

The disclosure is in the technical field of synthetic biology and metabolic engineering. More particularly, the disclosure is in the technical field of cultivation or fermentation of metabolically engineered cells. The disclosure describes a cell metabolically engineered for production of a mixture of at least four different neutral non-fucosylated oligosaccharides. Furthermore, the disclosure provides a method for the production of a mixture of at least four different neutral non-fucosylated oligosaccharides by a cell as well as the purification of at least one of the oligosaccharides from the cultivation.

The invention discloses a genetically engineered bacterium and its application in the preparation of sialyllactose. The genetically engineered bacterium has an N-acetylneuraminic acid biosynthesis pathway, includes multiple copies of a gene neuB for encoding sialic acid synthase, and the gene neuB is initiated for expression by a strong promoter. Using the genetically engineered bacteria of the invention to produce sialyllactose has the advantages of high yield and low overall cost.

This disclosure is in the technical field of synthetic biology and metabolic engineering. More particularly, this disclosure is in the technical field of fermentation of metabolically engineered yeast or fungal cells. This disclosure describes a method for the extracellular production of a di- or oligosaccharide that is derived from UDP-GlcNAc by a yeast or fungal cell as well as the separation of the di- or oligosaccharide from the cultivation. Furthermore, this disclosure provides a metabolically engineered yeast or fungal cell for extracellular production of a di- or oligosaccharide that is derived from UDP-GlcNAc and that is synthesized in the cytosol.

The present invention relates to a method of screening a target metabolite-overproducing mutant strain using a synthetic suicide genetic circuit, and more particularly to a method of screening only a metabolite-overproducing mutant strain while killing a mutant strain that does not produce the metabolite, by introducing into mutant strains a synthetic suicide genetic circuit comprising a suicide gene coupled with a riboswitch. The method for screening a target metabolite-overproducing mutant strain according to the present invention has advantages in that a metabolite-overproducing mutant strain having a relatively fast or slow growth rate can be separated by visual observation, and in that the riboswitch that is used in the synthetic suicide genetic circuit can be replaced depending on the kind of target metabolite, and thus the synthetic suicide genetic circuit can be applied commonly to various strains.

The present invention relates to the field of bio-production of chondroitin. There is a need in the art for chondroitin production methods allowing its highly efficient synthesis and secretion. The solution proposed in the present invention is the use of a recombinant cell, in particular a recombinant yeast, comprising many modifications as described in the present text. The present invention further proposes methods allowing the bio-production of chondroitin using the recombinant cell, in particular a recombinant yeast, of the invention.

Mammalian milk oligosaccharides (MMO) are produced in plants engineered to express recombinant MMO biosynthetic pathways.