The present invention provides at least two modified gene sequences, Sequence 1 comprising of nucleotide sequence of SEQ. ID no.1, and Sequence 2 comprising of nucleotide sequence of SEQ. ID no.2, encoding the enzyme choline oxidase wherein the gene sequences have been obtained by modifying the codA gene (Accession no. X84895) encoding choline oxidase from Arthrobacter globiformis, and a method to enzymatically produce betaine using choline oxidases encoded by Sequence 1, and Sequence 2, wherein the enzymatically produced betaine has minimal undesired trimethylamine contamination.