Abstract

 
 
 
 
 Crude lipase (acetone powder) was extracted from freshly sprouted melon seeds (Cucumeropsis manni). The activity, kinetic properties (effect of time, pH, and enzyme and substrate concentration, respectively) as well as the ability of the crude lipase to catalyze the production of methyl esters (biodiesel) were examined. The enzyme activity was determined using n-hexane as the solvent (1:2 v/w solvent: substrate ratio) and the transesterification product was analyzed by HPLC. A linear relationship was observed between reaction time and rate of lipolysis with the optimal activity at 2hr of incubation. Furthermore, the lipase was optimally active at acid pH 5 and lipolysis was achieved optimally when the amount of enzyme was 2.0g. Rate of lipolysis was observed to increase linearly at concentrations up to 5.0g of substrate above which a drop in the rate, with no apparent decrease in activity, was observed. The Km (6.25g) and Vmax (13.33%FFA/hr) were also determined. Analysis of the transesterification product yielded 0.61% alkyl ester, 0.81 %FFA, 93.17% TAG, 4.15% 1, 3-DAG and 1.26% 1, 2-DAG while transesterification efficiency was determined to be at 0.588%. Biodiesel (alkyl esters) prepared with the crude lipase was had a density of 0.872 g/mL while its cloud and pour points were 22°C and 12°C, respectively. The results from this research showed that an active lipase was isolated from sprouted melon seeds. However, the fuel properties of the biodiesel produced did not meet international transportation fuel standards. In order to be used industrially, better reaction conditions need to be established for the lipase.
 
 
 
 
Highlights
Analysis of the transesterification product: To determine the ability of the crude lipase to convert Refined Bleached Deodorized (RBD) palm oil to its alkyl ester with ethanol, the transesterification product was analyzed by HPLC at a facility in the US Department of Agriculture, USA
The result obtained in this study revealed lipase activity in sprouted seeds of Cucumeropsis mannii seeds
The cloud and pour points of the RBD palm oil methyl ester prepared with the lipase was 220C and 120C respectively
Summary
Biodiesel refers to a family of products made from vegetable oils or animal fats and alcohol (methanol or ethanol) These products are called alkyl esters of fatty acids. Transesterification of vegetable oils or animal fats, catalyzed either by a chemical catalyst (acid or base) or biological catalyst (lipases), is the most effective process for the transformation of triglyceride molecules into smaller, straight-chain molecules of alkyl-esters (Noureddini et al, 1998). The most interesting research today is focused on the utilization of lipases for catalyzing the synthesis of simple esters of vegetable oils or other agriculture lipid feedstock with or without the presence of organic solvents In spite of their potential industrial applications lipase-catalyzed transesterification remains to be adopted commercially on a broad scale due to high catalytic cost and slow reaction rates (Haas, 2004). The aim of this study is to extract, characterize and study the kinetic and transesterification properties of Cucumeropsis mannii lipase, with a view of producing cheaper and effective lipase for the production of biodiesel in future
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