Crude rice bran lipase was used for the enzymatic synthesis of Oleic Acid Ethyl Ester (OAEE) in a fed-batch system. It was found that rice bran contains protease (4.19 U/g) and lipase (324.03 U/g). The results show that protease inhibits lipase at a low concentration of ethanol (5 μ mol/ml), in which lipase esterifi cation activity was only 45.02 U/g. However, protease activity decreased about 11 times at a higher concentration of ethanol (5 -50 μ mol/ml). It resulted in an increase in the esterifi cation activity of lipase (324.03 U/g). This fi nding could be used for explaining the effects of ethanol on the enzymatic synthesis of OAEE using crude rice bran lipase in a fed-batch system. When the ethanol concentration in the reaction system was low ( Յ 4 μ mol/ml), the fi nal OAEE conversion was only 30%. It was caused both by the inhibition of lipase by rice bran protease and by the effect of low ethanol concentration on the equilibrium position of the lipasecatalysed esterifi cation reaction. However, the fi nal OAEE conversion reached 76 -92% when higher ethanol concentrations (12.5 -50 μ mol/ml) were added at initial reaction. It is suggested that the addition of higher ethanol concentrations (12.5 -50 μ mol/ml) into the reaction system may reduce protease activity and also increase ethanol concentration in the reaction system to be converted into OAEE.

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A fed-batch system was modified for the enzymatic production of Oleic Acid Ethyl Ester (OAEE) using rice bran (Oryza sativa) lipase by retaining the substrate molar ratio (ethanol/oleic acid) at 2.05:1 during the reaction. It resulted in an increase in the ester conversion of up to 76.8% in the first 6 h of the reaction, which was then followed by a decrease from 76.8% to 22.9% in 6 h later. The production of water in the reaction system also showed a similar trend. The water was hypothesized to lead lipase to reverse the reaction which resulted in a decrease in both (water and esters) in the last 6 h of the reaction. In order to overcome the problem, zeolite powder (25 and 50 mg/mL) were added into the reaction system at 5 h of the reaction. As the result, the final ester conversions increased drastically up to 90 -95.7%. Thus, the combination of a constant substrate molar ratio (ethanol/oleic acid) during the reaction (at 2.05:1) with the addition of zeolite powder (25 and 50 mg/mL) to the reaction system at 5 h is effective for the enzymatic synthesis of OAEE.

Bioethanol is an alternative energy source that is increasingly needed along with the depletion of petroleum stocks. Bioethanol can be produced by utilizing various wastes, including jackfruit peel and a mixture of crude cellulose enzymes from Trichoderma reesei and Aspergillus niger as well as fermentation using Saccharomyces cerevisiae and Zymomonas mobilis. This study aimed to compare the production of bioethanol using S. cerevisiae and Z. mobilis in fermented jackfruit peel with a mixture of crude cellulose enzymes from T. reesei and A. niger. The experimental design used a completely randomized design with the ratio of crude cellulase enzymes from T. reesei and A. niger as independent variables (0:0), (1:0), (0:1), (1:1), (1:2), (2:1), (1:3), and (3:1) as well as sugar and ethanol content as dependent variables. The sugar content was determined using the DNS method, while the ethanol content was determined using an alcoholmeter. Data analysis used one way ANOVA assisted by SPSS 16. The results showed that the highest sugar content (14.21 percent) was obtained in the ratio of crude cellulase enzymes T. reesei and A. niger (1:3), while the highest ethanol content (3, 16 percent) at a ratio of 1: 2 and fermented using Z. mobilis.

Recently, the fatty acid ethyl ester has been synthesized in place of fatty acid methyl ester since ethanol has been more renewable. In this research, oleic acid ethyl ester (OAEE) was synthesized using germinated jatropha seeds (Jatropha curcas.L) and rice bran (Oryza sativa) as source of lipase. The objective of the research was to optimize the synthesis conditions using Response Surface Methodology. Factors, such as crude enzyme concentration, molar ratio of oleic acid to ethanol, and the reaction time, were evaluated. The results show that lipase from germinated jatropha seeds had the hydrolitic and esterifi cation activity about 6.73 U/g and 298.07 U/g, respectively. Lipase from rice bran had the hydrolitic and esterifi cation activity about 10.57 U/g and 324.03 U/g, respectively. The optimum conditions of esterifi cation reaction using germinated jatropha seed lipase as biocatalyst were crude enzyme concentration of 0.31 g/ml, molar ratio of oleic acid to ethanol of 1 : 1.81, and reaction time of 50.9 min. The optimum conditions of esterifi cation reaction using rice bran lipase were crude enzyme concentration of 0.29 g/ml, molar ratio of oleic acid to ethanol of 1 : 2.05, and reaction time of 58.61 min. The obtained amounts of OAEE were 810.77 μmole and 626.92 μmole for lipases from rice bran and germinated jatropha seed, respectively.