Enzymatic esterification of kojic acid and palmitic acid by immobilized lipase for synthesis of kojic acid palmitate
Kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone) is an organic acid produced from various carbon sources in an aerobic fermentation by many species of Aspergillus, Penicillium and Acetobacter. The importance of kojic acid (KA) is recently focused on its role as whitening agent in cosmetic formu...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2015
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/71060/1/FBSB%202015%20175%20-%20IR.pdf |
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| Summary: | Kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone) is an organic acid produced from
various carbon sources in an aerobic fermentation by many species of Aspergillus,
Penicillium and Acetobacter. The importance of kojic acid (KA) is recently focused on
its role as whitening agent in cosmetic formulation. Kojic acid is water soluble and has
low stability towards light exposure. KA has also been criticized for weak depigmenting
effect and unstable for long storage. The hydrophilic property of KA has restricted its
application in cosmetic, oily food and pharmaceutical products. In order to improve the
chemical and biological activities of KA, its derivatives with new and improved chemical
properties and biological activities needs to be developed. Various KA derivatives such
as KA esters have been synthesized at industrial scale. KA esters are normally produced
via chemical process where strong acid or alkali is used. This chemical process is not
environmentally friendly and also produces complex mixtures that make the product
purification difficult and high cost.
The possibility of using lipase, lipozyme RMIM, in the esterification of KA with
palmitic acid (PA) in acetone to synthesize KA palmitate (KAP) was investigated in this
study. Preliminary, the effects of organic solvent, substrate ratio, enzyme loading,
temperature and reaction time on the yield of KAP were evaluated. The appropriate
ranges for each variable were subsequently used for optimization using response surface
methodology (RSM). The optimal reaction condition for ester production was then
applied in 500 mL stirred tank reactor (STR) using two types of impeller [Rushton
turbine (RT) and Pitch blade disc turbine (PBDT)] to investigate the effect of agitation
speed on the esterification performance. Among the organic solvent tested for
esterification to synthesize KAP, acetone was the preferred solvent. Optimal conditions
for esterification as suggested by RSM were as follows: PA to KA ratio, 6.74; enzyme
loading, 0.59 g; reaction temperature, 45.9°C and reaction time, 20 h, which gave the
percentage of esterification of 64.47%. For the esterification in STR, the percentage yield
of KAP was significantly higher for RT than PBDT at all agitation speeds tested (150 to
450 rpm). The highest yield of KAP (82.14%) was obtained in STR with RT agitated at
250 rpm. Results from this study have demonstrated that substantially high yield of KA
esters could be produced by enzymatic esterification using lipase. This alternative method has potential to be used industrially. Since the use of hazardous chemical can be
minimized, enzymatic synthesis of KA esters is more natural and appears to be more
appealing to the customers than the chemical process. |
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