Esterification of free fatty acids by Rhizopus oryzae as cell-catalyzed from used cooking oil for biodiesel production.

2 Abstract: Biodiesel fuel, as fatty acid methyl ester is produced by esterification of plant oil or animal fat with methanol. This renewable fuel resource is an attractive alternative for the replacement of petroleum based fuels. Utilization of the whole cell as biocatalyst instead of free or immobilized enzyme is a new approach to reduce the catalysts costs in lipase-catalyzed biodiesel production. In this research work, the immobilized cell of Rhizopus oryzae (PTCC5174) in biomass support particles (BSPs) was used for the methanolysis of used cooking oil (UCO). The inhibitory effect of the undissolved methanol on lipase activity was eliminated by stepwise addition of methanol to the reaction mixture. Initially, the UCO was filtered by a Whatman 42 filter paper and then the filtered UCO was heated to 100°C. The pretreated UCO was converted to biodiesel using methanol to fatty acid molar ratio of 3:1, at 35°C. In the final step, BSPs of the immobilized cells of R. oryzae were added for 72 h. The free acid to methyl esters conversion for the filtered UCO was only 46%. The free acids were to methyl esters conversion for the heated and filtered UCO enhanced to 88%. The untreated UCO and the methyl ester produced were analyzed using GC-MS chromatography. The heated UCO is cost effective and simple method for the large scale biodiesel production of whole cell-catalyzed methanolysis.