Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides

Hemicelluloses are heterogeneous branched polymers of sugars that exist abundantly in nature. Enzymatic hydrolysis is envisioned as a highly potential method in converting hemicelluloses into fuels and value-added chemicals. However, the use of free enzyme is hampered by low operational stability, d...

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Main Author:	Md. Shaarani @ Md. Nawi, Shalyda
Format:	Thesis
Language:	English
Published:	2018
Subjects:	TP Chemical technology
Online Access:	http://eprints.utm.my/id/eprint/81425/1/ShalydaMdShaaraniPFChE2018.pdf
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spelling	my-utm-ep.814252019-08-23T04:07:19Z Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides 2018 Md. Shaarani @ Md. Nawi, Shalyda TP Chemical technology Hemicelluloses are heterogeneous branched polymers of sugars that exist abundantly in nature. Enzymatic hydrolysis is envisioned as a highly potential method in converting hemicelluloses into fuels and value-added chemicals. However, the use of free enzyme is hampered by low operational stability, difficulty in recovery and non-reusability, which requires for enzyme immobilization. Carrier-bound immobilization leads to utilization of high cost matrices, clogging of filters during downstream processing and presence of large amounts of non-catalytic ballast. Therefore, cross-linked enzyme aggregates (CLEA), a carrier-free technology that combines purification (precipitation) and immobilization into a single operation and does not require purified enzymes, is the solution to these problems. In this study, a recombinant xylanase (Xyl) from Trichoderma reesei was immobilized using three approaches: Xyl-CLEA, Xyl-CLEA-BSA (bovine serum albumin) and Xyl-CLEA-silanized maghemite. The use of ethanol as precipitant (1:9 volume ratio of enzyme to precipitant), glutaraldehyde (0.2:1 of glutaraldehyde to enzyme of 100 mM concentration) as cross-linking agent and the introduction of (3-aminopropyl) triethoxysilane (APTES) silanized maghemite (0.0075:1 of silanized maghemite to enzyme) prevailed in forming xylanase CLEAs with good enzyme activity recovery (78 %), thermal stability (50 % retained activity) and reusability (50 % retained activity). The Xyl-CLEA-silanized maghemite enhanced the activity recovery 1.66- and 1.50-fold compared to Xyl-CLEA and Xyl-CLEA-BSA, respectively. At elevated temperature of 60 °C and pHs of 3.0 and 8.0, Xyl-CLEA-silanized maghemite achieved better stability compared to the other CLEAs and free enzyme. Xyl-CLEA-silanized maghemite also successfully retained more than 50 % of its activity after 6 cycles, whereas Xyl-CLEA only retained approximately 10 % after 5 cycles. Therefore, the performance of Xyl-CLEA-silanized maghemite was further investigated by xylan hydrolysis under optimised reaction conditions. Xylooligosaccharides yield was slightly improved by 1.26- fold compared to the free enzyme. Kinetic parameters confirmed that CLEA immobilization did affect the productivity of the designed biocatalyst. 2018 Thesis http://eprints.utm.my/id/eprint/81425/ http://eprints.utm.my/id/eprint/81425/1/ShalydaMdShaaraniPFChE2018.pdf application/pdf en public http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:119483 phd doctoral Universiti Teknologi Malaysia Chemical and Energy Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TP Chemical technology
spellingShingle	TP Chemical technology Md. Shaarani @ Md. Nawi, Shalyda Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides
description	Hemicelluloses are heterogeneous branched polymers of sugars that exist abundantly in nature. Enzymatic hydrolysis is envisioned as a highly potential method in converting hemicelluloses into fuels and value-added chemicals. However, the use of free enzyme is hampered by low operational stability, difficulty in recovery and non-reusability, which requires for enzyme immobilization. Carrier-bound immobilization leads to utilization of high cost matrices, clogging of filters during downstream processing and presence of large amounts of non-catalytic ballast. Therefore, cross-linked enzyme aggregates (CLEA), a carrier-free technology that combines purification (precipitation) and immobilization into a single operation and does not require purified enzymes, is the solution to these problems. In this study, a recombinant xylanase (Xyl) from Trichoderma reesei was immobilized using three approaches: Xyl-CLEA, Xyl-CLEA-BSA (bovine serum albumin) and Xyl-CLEA-silanized maghemite. The use of ethanol as precipitant (1:9 volume ratio of enzyme to precipitant), glutaraldehyde (0.2:1 of glutaraldehyde to enzyme of 100 mM concentration) as cross-linking agent and the introduction of (3-aminopropyl) triethoxysilane (APTES) silanized maghemite (0.0075:1 of silanized maghemite to enzyme) prevailed in forming xylanase CLEAs with good enzyme activity recovery (78 %), thermal stability (50 % retained activity) and reusability (50 % retained activity). The Xyl-CLEA-silanized maghemite enhanced the activity recovery 1.66- and 1.50-fold compared to Xyl-CLEA and Xyl-CLEA-BSA, respectively. At elevated temperature of 60 °C and pHs of 3.0 and 8.0, Xyl-CLEA-silanized maghemite achieved better stability compared to the other CLEAs and free enzyme. Xyl-CLEA-silanized maghemite also successfully retained more than 50 % of its activity after 6 cycles, whereas Xyl-CLEA only retained approximately 10 % after 5 cycles. Therefore, the performance of Xyl-CLEA-silanized maghemite was further investigated by xylan hydrolysis under optimised reaction conditions. Xylooligosaccharides yield was slightly improved by 1.26- fold compared to the free enzyme. Kinetic parameters confirmed that CLEA immobilization did affect the productivity of the designed biocatalyst.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Md. Shaarani @ Md. Nawi, Shalyda
author_facet	Md. Shaarani @ Md. Nawi, Shalyda
author_sort	Md. Shaarani @ Md. Nawi, Shalyda
title	Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides
title_short	Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides
title_full	Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides
title_fullStr	Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides
title_full_unstemmed	Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides
title_sort	cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides
granting_institution	Universiti Teknologi Malaysia
granting_department	Chemical and Energy Engineering
publishDate	2018
url	http://eprints.utm.my/id/eprint/81425/1/ShalydaMdShaaraniPFChE2018.pdf
_version_	1747818328614764544

Cross-linked enzyme aggregates of recombinant xylanase for conversion of hemicelluloses to xylooligosaccharides

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