Disclosed herein are bacteria engineered to treat diseases associated with hyperammonemia and methods of use thereof. Specifically, the bacteria are engineered to comprise a racemase to enable the detection of non-naturally occurring metabolites as an indication that the engineered bacteria are effectively converting ammonia.

A genetically modified diazotrophic microbe is genetically modified to produce ?-polyglutamic acid (?-PGA). In one or more embodiments, the diazotrophic microbe is Azotobacter vinelandii. In one or more embodiments, the diazotrophic microbe is genetically modified to use a non-sugar carbon source.

The present disclosure provides a novel recombinant unidirectional asparagine racemase for the conversion of L-asparagine to D-asparagine. Such unidirectional asparagine racemase could be used in treating cancers (e.g., leukemias or lymphomas) that require exogenous L-asparagine. This innovative design offers a promising new approach to reduce detrimental side effects caused by current therapies.

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.