Characterization and compositional analysis of highly acidic karanja oil and its potential feedstock for enzymatic synthesis of biodiesel

Abstract

In the present study, we focused on the synthesis of biodiesel from Pseudomonas cepacia, crude karanja oil by the process of enzymatic transesterification using bio-support materials, such as lipase immobilized on polyvinyl alcohol/AlgNa. Enzymatic transesterification has taken over chemical methods due to its milder nature and environmental friendliness. 2-Propanol was utilized as an acyl acceptor during the biodiesel preparation. The optimized conditions for crude karanja (Pongamiapinnata) oil transesterification were 10% lipase (immobilized Pseudomonas cepacia lipase) based upon the oil weight, and a molar ratio of 6 : 1 between alcohol and oil at 50 ± 1 °C for 24 h. The maximum product obtained from crude karanja oil by using 2-propanol was 72.85%, while the conversion of biodiesel was calculated to be 75.16% during the 24 h. The results from this study showed the feasibility of economical biodiesel production using crude karanja oil product. Recyclability of the bio-support catalyst was studied for 11 cycles using 2-propanol as the acyl acceptor in the absence of a solvent under standard conditions. After the operation of 6 cycles, the bio-support catalyst could hold up to 71% of its initial yield of biodiesel. Physicochemical characteristics of the crude karanja oil were determined to evaluate its suitability for the production of biodiesel. The as-prepared karanja oil exemplified the composition of 9.75% linolenic, 6.24% linoleic acid, 60.25% oleic and 23.76% saturated acyl groups according to the proton nuclear magnetic resonance (¹H NMR)spectrum. The characteristics of crude karanja oil and biodiesel were analyzed as per ASTM D6751 and they were within the specifications. ¹H NMR analysis confirmed the formation of biodiesel.