Xylitol from oil palm empty fruit bunch by Candida guilliermondii / fermentation and kinetic study
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Date
2009-04
Authors
Sulaiman, Manzailatul Airenne
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Abstract
Oil palm empty fruit bunch (OPEFB) is one of the main wastes generated by
palm oil mills. This waste is widespread, cheap and renewable and be selected as raw
materials for xylitol production as it contains hemicellulose, comprising xylan that
can be hydrolysed to xylose. As the xylitol content is very low in other natural
sources, a low cost material with high content of xylose is identified as the starting
material.
Analysis of oil palm empty fruit bunch fibers showed that there were 5 main
compounds namely xylose, glucose, lignin, acetic acid and furfural. The highest
compound concentration was detected for xylose at 36.54 giL. This showed that an
oil palm empty fruit bunch was a suitable material for the production of'xylitol.
In hydrolysis process, the highest xylose production was detected at 120°C,
15 min reaction time with 6% sUlphuric acid at 28.97 giL. The hydrolysis process
was prolonged up to 300 min in order to determine the production of inhibitor
components such as acetic acid and furfural, and also the presence of other sugar
component such as glucose. In neutralization and detoxification process, the
. combination of calcium oxide and activated charcoal treatment showed the highest
reduction of inhibitors, which was up to 69% on acetic acid and 61 % on furfural
concentration.
For fermentation process, Candida guilliermondii FTI 20037 was chosen as a
biocatalyst for the conversion of xylose to xylitol. In synthetic media, the hi.ghest
xylitol production was obtained in Media 1 at pH 3.5, 250 rpm, initial substrate
concentration 250 giL and inoculum size at 10 giL. Production of xylitol using
detoxified and non-detoxified media showed that the yield of xylitol per xylose
concentration (Yp/s) were 0.73g/g and 0.6 gig, respectively. This showed that
detoxified media was much better substrate compared to non-detoxified media.
An unstructured model taking into account growth, xylitol production and
substrate consumption were compared. It was found that Logistic model fitted well
with C guilliermondii growth and substrate consumption, while Leudeking-piret
model was for xylitol production. For substrate inhibition, Andrew model fitted well
with the experimental observation with R2 =0.94. The optimization process was
performed to find out the optimum condition that lead to the highest production of
xylitol using Random Surface Methodology (RSM). The optimum condition for
xylitol production was observed at pH 3.5, 250 rpm agitation rate and 10 giL of
inoculum size.
Xylitol was crystallized at -10°C using different concentration of synthetic
and fermented media. The crystallization for both media took 4 hr and 10 hr,
respectively. This could be due to the presence of other impurities in the media. At
the highest xylitol concentration at 597 giL, 0.49g/g xylitol crystal yield was
obtained with 91.05% of crystal purity.
Description
Keywords
Analysis of oil palm empty fruit bunch fibers showed that , 5 main compounds namely xylose, glucose, lignin, acetic acid and furfural