Laccase production by locally-isolated Trichoderma sp. IS1037 using rubberwood dust for biobleaching of soda bamboo pulps
Conventional pulp bleaching of lignocellulosic materials using chlorine and its compounds leads to the generation of toxic compounds including chlorolignins. Therefore a study on biobleaching of lignocellulosic material was carried out as an alternative for pulp bleaching purpose. This study focu...
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Format: | Thesis |
Language: | English |
Published: |
2017
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Online Access: | http://psasir.upm.edu.my/id/eprint/70301/1/FBSB%202017%2030%20IR.pdf http://psasir.upm.edu.my/id/eprint/70301/ |
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Summary: | Conventional pulp bleaching of lignocellulosic materials using chlorine and its
compounds leads to the generation of toxic compounds including chlorolignins.
Therefore a study on biobleaching of lignocellulosic material was carried out as an
alternative for pulp bleaching purpose. This study focused on the use of laccase from
Trichoderma sp. IS1037 for bamboo pulp biobleaching. The laccase enzyme was
produced from a local fungi isolate Trichoderma sp. IS1037. The possibility of using
crude laccase for bleaching bamboo soda pulp by combining it with bleaching
chlorine agents was also studied. A total of five native fungi was screened to
determine the potential producer of laccase enzyme. The fungi isolate was identified
by utilizing the Biolog Kit and molecular assay. Optimization of culture condition
for laccase production was carried out using seven selected parameters known as
carbon source, nitrogen source, temperature, pH, agitation speed, concentration of
CuSO4, and surfactant. The crude laccase produced was used for the pretreatment of
bleaching process on unbleached bamboo soda pulp. Optimization of temperature,
pH and reaction time on crude laccase pretreatment of bamboo pulp was investigated
using response surface method (RSM) followed by chemical bleaching sequences
D1EPD2. In order to evaluate the decrease in lignin content, adsorbable organic
halogens (AOX), hexenuronic acid (HexA) and chemical oxygen demand (COD)
were tested. Solid phase extraction was conducted to extract AOX from effluent after
bleaching process and HPLC was aplied to determine AOX concentration. HexA
was conducted using UV spectrophotometer. The result from screening
demonstrated that laccase produced from locally isolated fungi identified as
Trichoderma sp. IS1037 under optimized condition was 65.0 U/ml which is 11 fold
higher than the production of the control culture 5.8 via submerged fermentation
strategy. The optimum condition for laccase production was 30 °C, 4.5 and 150 rpm
for temperature, initial pH media and agitation speed, respectively, using rubberwood dust as a carbon source together with organic nitrogen source (peptone,
yeast extract and malt extract). The effects of copper sulphate and Tween 80 were
found significant in improving the extracellular laccase production. In pretreatment
of bamboo pulp using laccase under optimized condition has decreased lignin by
64% and hemicellulose by 50% content was achieved at pH, temperature and
reaction time of 4, 50 °C and 4 hours, respectively. XRD and FTIR analysis showed
an increase in relative crystallinity of cellulose and delignification due to
hydroxylation and exfoliation of amorphous regions through laccase pretreatment. In
addition, there were significant result found in the reduction of AOX, COD, HexA
and lignin by the enzymatic pretreatment. The AOX content of bamboo pulp was
reduced by 29%, 34% for biobleaching and modified sample respectively. Moreover,
HexA results revealed decrement in content with 1.44% to 1.42% for biobleaching
and modified sample respectively. Therefore, the pretreatment of bamboo pulp by
laccase has considerable benefit on reducing the organic compound of AOX, COD,
HexA and chemical composition in different sequence bleaching. The outcomes
presented in this study could contribute to the future study on the production of
laccase enzyme from Trichoderma sp.IS1037 for various industrial applications
including pulp and paper industry. |
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