Cross-linked enzyme aggregates from rice (Oryza sativa) bran as sturdy biocatalysts for the transesterification of coconut oil with methanol for the preparation of coconut biodiesel

Date

4-2014

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Milagros M. Peralta

Restrictions

Restricted: Not available to the general public. Access is available only after consultation with author/thesis adviser and only to those bound by the confidentiality agreement.

Abstract

A lipase from rice bran was investigated as a biocatalyst in the transesterification of coconut oil for the production of biodiesel. Rice bran was obtained from rough rice by milling and the crude lipase was extracted using sodium phosphate buffer with calcium chloride. The crude lipase was partially purified by ammonium sulfate (AS) precipitation. The protein content of the crude enzyme and the AS fractions was determined using the Bradford assay. Specific lipase activity of the ammonium sulfate fractions was determined by titrimetric method using olive oil as the substrate. It was found that maximum lipase activity was concentrated in the 20% AS precipitate fraction which had a specific activity of 0.030 U/g, corresponding to about 1.67x greater activity relative to the crude rice bran lipase. This result indicated that the rice bran lipase seemed to have a relatively hydrophobic surface since only a low amount of ammonium sulfate was necessary to precipitate the enzyme. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), confirmed that the 20% AS precipitate, which exhibited the highest lipase activity among the AS fractions, contained a major protein band with a molecular weight of 32 kDa. From the literature data, rice bran lipase can be classified as a Type II lipase based on its MW of 32 kDa by SDS-PAGE. Stabilization of rice bran lipase was achieved by cross-linking of the lipase with glutaraldehyde. The production of rice bran lipase crosslinked enzyme aggregates (CLEA) was found to be optimum at pH 7.5 and 45c. Under these conditions, the activity of the rice bran lipase CLEA was found to be 1.491 U/g, which corresponds roughly to 83x greater activity relative to the crude native enzyme. The rice bran lipase CLEA was used in the transesterification of coconut oil for the synthesis of biodiesel. The enzyme-catalyzed reaction was found to be complete in 4 hours by silica gel thin layer chromatography as seen from the complete disappearance of the triglyceride spot and the increase in intensity of the spot corresponding to the fatty acid methyl ester. The rice bran lipase CLEA was found to retain 50% of its original activity after 7 cycles of olive oil hydrolysis. The average yield of the reaction was found to be 96% based on the isolated fatty acid methyl esters which were identified using GC-MS and FT-IR spectroscopic analysis.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2014 C42 /C78

Document Type

Thesis

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