The present disclosure provides recombinant Staphylococcus bacterium (e.g. S. epidermidis) that are dependent on D-alanine for growth. In one aspect, the disclosure features a recombinant Staphylococcus bacterium comprising two inactivated alanine racemase genes (?alr1?alr2); and an inactivated D-alanine aminotransferase (dat) gene. In another aspect, the disclosure features a method of making the recombinant Staphylococcus bacterium.

Disclosed herein are recombinant Listeria strains comprising nucleotides encoding two or more heterologous antigens each fused to a truncated LLO, an N-terminal ActA or a PEST-sequence, methods of preparing same, and methods of inducing an immune response, and treating, inhibiting, or suppressing cancer or tumors comprising administering same.

The present invention relates to the field of chemical manufacture. In particular, it relates to a method for manufacturing racemic methylglycinediacetic acid (MGDA) comprising the steps of contacting a solution comprising or being enriched in D-alanine or L-alanine to an alanine racemase at a temperature of at least 50? C. and alkaline conditions for a time sufficient to allow conversion of said solution into a racemic alanine solution, obtaining a racemic alanine solution, and chemically converting the racemic alanine into racemic MGDA. The invention further contemplates an alanine racemase which is capable of converting a solution comprising or being enriched in D-alanine or L-alanine into racemic alanine solution at a temperature of at least 50? C. and under alkaline conditions as well as the use of said alanine racemase for converting a solution comprising or being enriched in D-alanine or L-alanine into racemic alanine solution at a temperature of at least 50? C. and under alkaline conditions.

The present invention provides Listeria vaccine strains that express a heterologous antigen and a metabolic enzyme, and methods of generating same.

The present disclosure provides recombinant Staphylococcus bacterium (e.g. S. epidermidis) that are dependent on D-alanine for growth. In one aspect, the disclosure features a recombinant Staphylococcus bacterium comprising two inactivated alanine racemase genes (alr1alr2); and an inactivated D-alanine aminotransferase (dat) gene. In another aspect, the disclosure features a method of making the recombinant Staphylococcus bacterium.

The present invention provides Listeria vaccine strains that express a heterologous antigen and a metabolic enzyme, and methods of generating same.

The present invention provides Listeria vaccine strains that express a heterologous antigen and a metabolic enzyme, and methods of generating same.

The present invention relates to the technical field of genetic engineering and fermentation engineering, and specifically discloses a preparation method of an N-acetyl-D-amino acid. An L-amino acid and/or a D, L-amino acid are used as raw materials, the L-amino acid is converted into a D-amino acid under the action of an L-amino acid isomerase, and the D-amino acid is converted into an N-acetyl-D-amino acid under the action of an acyltransferase. General-use L-amino acid isomerase and acyltransferase are used to convert various amino acids into corresponding N-acetyl-D-amino acids. Raw materials used in the present method are low cost, toxic chemical racemization and high-cost chiral resolution steps are avoided, and the method is suitable for industrial processing and production. The prepared N-acetyl-D-amino acid can be further processed into a D-amino acid or a D-amino acid derivative.

The present invention discloses a DL-alanine-producing genetically engineered strain, as well as a method of construction and use thereof, and pertains to the field of bioengineering. According to the present invention, through enhancing the glycolysis pathway or/and introducing thermostable alanine dehydrogenase, a genetically engineered strain capable of high-yield production of alanine at 42 C. to 55 C. This strain can be used in a two-step method for producing racemic DL-alanine, which includes fermentation and subsequent addition of microbial alanine racemase. Through inactivating or deleting alanine racemase genes in this strain and then separately introducing overexpressed alanine racemase gene(s), a genetically engineered strain capable of producing racemic DL-alanine using a direct fermentation method can be constructed. When the original strain possesses a lactate synthesis pathway, blocking this lactate synthesis pathway in both the genetically engineered strains can additionally augment the proportion of a pyruvate synthesis pathway.

The present invention discloses an L-alanine-producing genetically engineered strain, as well as a method of construction and use thereof, and pertains to the field of bioengineering. According to the present invention, through enhancing the glycolysis pathway or/and introducing a gene for thermostable alanine dehydrogenase, a genetically engineered strain capable of high-yield production of alanine under a high temperature condition of 42 C. to 55 C. can be constructed. Moreover, through knocking out alanine racemase genes, optical purity of L-alanine can be significantly increased. When the original strain possesses a lactate synthesis pathway, blocking this lactate synthesis pathway can augment the proportion of a pyruvate synthesis pathway, resulting in an additionally increased yield of L-alanine. The present invention overcomes the problems of fermentation at a low temperature, high cost and the like, which arise from the use of conventional L-alanine production techniques, enables production of L-alanine by fermentation at a high temperature of 42 C. to 55 C. with a yield of 95 g/L or higher, and is of high value to industrial application.