Essential oils extraction from native or collective plants with eugenol basses such as Eugenia caryophyllata and Ocimum basilicum and bio-transformation to vanillin by Serratia marcescens (ATCC 13880) was investigated. The oils were obtained by steam distillation and were analyzed by UV and GC-MS. Essential oils with eugenol bases was added to resting phase of bacterium growth curve with final concentration of 20 gL−1 and incubated at 27°C and 150 rpm, for 24 hours to bioconversion to vanillin. Crystalline structure of vanillin was isolated and confirmed by GC-MS. Forthy-three and one hundred and fifteen compounds were identified in essential oil of Eugenia caryopyllata by using first and second methods and eugenol was determined as the major component with 88.205 % and 54.628 % respectively. Eugenol in essential oil of Ocimum basilicum was rare. The highest vanillin concentration, 0.6 gL−1, was obtained with 46 % purity from flower buds of Eugenia caryopyllata.