KINETIC ANALYSIS OF FATTY ACID ALKYL ESTERS USING WHOLE CELL BIOCATALYST AND LIPASE CATALYZED TRANSESTERIFICATION FROM WASTE COOKING OILB. BHARATHIRAJA1, R. RANJITHKUMAR, M. CHAKRAVARTHY, D. YOGENDRAN, P. VIVEK , D. YUVARAJ, R. PRAVEEN KUMAR AND S. PALANI
In the present scenario of energy crisis and depleting fossil fuels, there is a need for alternative fuels such as biodiesel. Waste cooking oil, a kitchen waste was analyzed as a potential source for biodiesel production by transesterification using four different acyl acceptors-Methanol, Isopropanol, Iso-butanol and Iso-amyl Alcohol in a solvent free system. In the present work transesterification was carried out using biocatalysts- lipase enzyme in purified form and as whole cell biocatalyst of filamentous fungi Rhizopus oryzae. First, an optimization of the reaction conditions and comparative analysis of the yields for both the catalyst was obtained. During our further study, a kinetic study for the enzyme catalyzed and whole cell catalyzed process was developed using Pingpong Bi-Bi Kinetics model with substrate competitive inhibition. Among the different acyl acceptors, methanol whose reaction parameters were optimized as 35°C, 1:3 (oil/alcohol), 24h, 150rpm and 10% lipase concentration (mass ratio to oil) showed maximum conversion of triglycerides to Biodiesel - 94% with Purified Enzyme and 84% with Whole Cell Biocatalyst. Kinetic model based Ping-pong Bi-Bi model with competitive substrate inhibition by alcohol was used to find the maximum reaction rate Vi for the four acyl acceptors using pure enzyme and Whole Cell Biocatalyst. The results showed the initial rate of reation was lower for whole cell biocatalyst which was mainly due to the reduced substrate diffusion through the cell membrane and this observation can be also supported by the fact that whole cell biocatalyst remained stable for longer time due to the reduced inhibitor exposure.
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