COMPARISON STUDY BETWEEN BASE AND FREE LIPASE ENZYME CATALYSED TRANSESTERIFICATION IN THE SYNTHESIS OF BIODIESEL FROM CARICA PAPAYA SEED OIL

The main objective of the present study was to evaluate the suitability of different catalyst usage in the production of biodiesel using papaya seed as the feedstock. Non-seasonal papaya seeds were bought from local market, oven-dried and oil was extracted with n-hexane solvent. Physiochemical analysis was done to the seed oil. Transesterification was carried out using methanol to oil in the ratio of 9:1 with base and lipase catalysts. Papaya seed yielded 34% of oil which makes it an attractive feed stock in the biodiesel synthesis. Extracted seed oil also had an Iodine value of 64.98 ? 0.97 (g I/100g), Saponification Value of 14.00 ? 9.90 (mg KOH/g), Free fatty acid content of 1.18 ? 0.41(%) and Unsaponifiable matter of 4.55(%). Biodiesel catalysed from base catalyst gave a yield of 90% while lipase catalyst gave 50% of biodiesel. Synthesised biodiesel samples did not show any corrosion to copper stripes. Moreover, combustion energy released and cetane number determined for biodiesel synthesised using base catalysed transesterification and lipase catalysed transesterification were 1255.8J/g and 1172.08J/g and 79 and 76 respectively. Base synthesised biodiesel was analysed using GC-MS analysis and it was determined that the major fatty acid methyl esters present in the sample were Palmitic acid, Trans-13-Octadenoic acid and Oleic acid in the percentages of 73.9%, 14.4% and 10.9% respectively. Hence, the results shows that this local agricultural waste has good potential as biodiesel feedstock and base catalyst is a better catalyst than free lipase enzymes in the biodiesel production.