synthesize enantiopure D-phenylglycine or D-4-hydroxyphenylglycine, the two important side-chains in high demand for the β-lactam antibiotics industry, in a single enzymatic step using L-glutamate as a lowcost amino donor. Biotechnological development in various aspects were attempted to make this enzymatic synthesis process effective and viable. Directed mutagenesis of dpgA gene to replace the C-terminus serine with cysteine could facilitate rapid and site specific immobilization of the D-PhgAT(S453C) on thiol-containing matrix while maintaining enzyme activity and enhancing its stability. Biocatalysis using the immobilized D-PhgAT(S453C) in a controlled-release system of Amberlite (IRA400)-adsorbed benzoylformate yielded a final Dphenylglycine concentration of 10.25 g.L-1. Two systems for D-PhgAT high-expression were developed. The first system was based on Escherichia coli host with chaperones coexpressions which improved the D-PhgAT yield from 0.44 to 1,768 unit.L-1.OD-1. In the second system, codon-optimized synthetic dpgA gene was expressed in Pichia pastoris with bacterial chaperones co-expressions which yielded D-PhgAT at 14,717 unit.L-1.OD-1. Problem of the inherently low solubility of the wild-type D-PhgAT was alleviated by structureguided mutagenesis which could increase the enzyme solubility from 11.5 to 51 mg/mL. During investigation of molecular and catalytic property of the D-PhgAT, a new method for determination of aminotransferase stereospecificity for C-4' hydrogen transfer on the coenzyme was developed. A spectrophotometric enzymatic cycling method using Lglutamate dehydrogenase and D-PhgAT for determination of L-glutamate in foods is another aspect of D-PhgAT application developed during this project. Genetically modification of the D-PhgAT to relief substrate inhibition, developing effective and logical systems for substrate addition and product removal are important research topics that should be done in the future.