The present invention provides a method for synthesizing nicotinic acid from 3-picoline using transformed recombinant host cells with synthetically designed gene constructs as whole cell biocatalysts. Adaptive engineering of aromatic ring metabolizing genes isolated from microorganisms enables efficient metabolism of 3-picoline. Mutants with enhanced activity profiles are developed through gene-level modifications, ensuring superior catalytic efficiency and stability. Synthetic biology techniques generate tailored coding sequences for optimum expression. Synthetic constructs embedded with engineered genes, ribosomal binding sites, and spacers are co-expressed within one cellular unit. A one-pot reaction system utilizes versatile plasmid vectors like pET28a(+) for efficient co-expression, advancing the host microorganism matrix. The invention integrates immobilized whole-cell catalysts, addressing catalyst reusability, stability, and industrial scalability. Enhanced cell permeability and oxygen incorporation improve reaction efficiency and substrate accessibility, offering a scalable, cost-effective solution for industrial bioconversion processes.