Disclosed is a microorganism of Escherichia sp. producing O-acetyl homoserine, and a method of producing O-acetyl homoserine in high yield using the microorganism.

Presented herein are biocatalysts and methods for converting C1-containing materials to organic acids such as muconic acid or adipic acid.

One or more genes in a biosynthesis pathway for a vitamin or other essential nutrient which is needed for the survival of a microorganism can be used as an effective selective marker to identify cells transformed with an exogenous nucleic acid. The microorganism does not naturally contain or express the one or more gene. This permits genetic manipulations to be performed. It permits lower cost fermentations to be performed. It permits production of the essential nutrient for subsequent commodity use.

The invention relates to norcoclaurine synthases and substrate binding sites having one or more site-specific mutation which increase the activity, when compared to the wild type synthase, of the condensation of 4-HPAA and dopamine to (S)-norcoclaurine and/or 3,4-DhPAA and dopamine to (S)-norlaudanosoline. The inventors both identified specific mutations corresponding to at position 73, 75, 77, 82, 99, 114, 141, 142, 147, 152, 174 and/or 178 in the count according to SEQ ID No: 1, and sites corresponding to the binding domains defined in SEQ ID NO: 4 and 5, where the mutated increase of the activity may be positioned within these norcoclaurine synthases. These domains are conserved regions.

Provided are modified santalene synthase polypeptides, nucleic acid molecules encoding the modified santalene synthase polypeptides, and methods of using the modified santalene synthase polypeptides. The modified santalene synthase polypeptides include those that catalyze production of increased levels of terpenes or altered profiles thereof or both.

The present disclosure provides DNA-guided CRISPR systems; polynucleotides comprising DNA, RNA and mixtures thereof for use with CRISPR systems; and methods of use involving such polynucleotides and DNA-guided CRISPR systems.

The invention provides a glutamate decarboxylase mutant with improved pH tolerance and use thereof in synthesis of gamma-aminobutyric acid. The mutant is obtained by mutating glutamate decarboxylase having an amino acid sequence as shown in SEQ ID NO. 3. The enzyme activity of the mutant at pH 6.5 is improved to 178% of the original enzyme (SEQ ID NO. 3). The final yield of 1000 g of substrate fed in batches in a 5 L tank for 12 h is up to 688.13 g/L, which is about 52% higher than the productivity of the original glutamate decarboxylase. The final molar conversion rate can reach 98.2%. The invention not only broadens the enzyme activity of GAD under the optimum pH, but also broadens the enzyme activity of GAD under the neutral pH, and enhances the capability of the GAD to synthesize gamma-aminobutyric acid, and therefore is more suitable for industrial production.