Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase

The microbial production of xylitol has been studied extensively as an alternative to the chemical process, which on an industrial-scale is time-consuming mainly due to sterilization, inoculum development and product recovery problem. Apart from using pure xylose, no other substrate has been propose...

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Main Author:	Islam, S. M. Rafiqul
Format:	Thesis
Language:	English
Published:	2012
Subjects:	TP Chemical technology
Online Access:	http://umpir.ump.edu.my/id/eprint/37083/1/SYNTHESIS%20OF%20XYLITOL%20FROM%20MERANTI%20WOOD%20SAWDUST%20IN%20BATCH.pdf
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spelling	my-ump-ir.370832023-02-22T02:38:52Z Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase 2012-11 Islam, S. M. Rafiqul TP Chemical technology The microbial production of xylitol has been studied extensively as an alternative to the chemical process, which on an industrial-scale is time-consuming mainly due to sterilization, inoculum development and product recovery problem. Apart from using pure xylose, no other substrate has been proposed for xylitol synthesis using xylose reductase (XR). The aim of this study was to synthesize xylitol, a specialty product, from Meranti wood sawdust hemicellulosic hydrolysate (MWSHH) by locally produced XR. MWS is a sawmill waste, which can be a promising source of xylose for xylitol production. The kinetic parameters of mathematical models were determined to predict xylose, glucose, furfural, and acetic acid concentration in the hydrolysate. Optimization of MWS hydrolysis was conducted with statistical design including onefactor-at-a-time (OFAT) method for maximum xylose recovery. The results of OFAT indicated the residence time, temperature, and acid concentration to be the major factors improving xylose recovery with a value of 60 min, 125 ºC, and 4%, respectively. These factors were further optimized by response surface methodology (RSM), and the optimum values obtained were 80 min, 124 ºC, and 3.26%, respectively. Under these conditions xylose yield and selectivity were attained at 90.6% and 4.05 g/g, respectively. XR was isolated from adapted C. tropicalis and characterized. The activity of NADPH-dependent XR measured was 11.16 U/mL. It was stable at pH 5.0–7.0 and temperature of 25–40 ºC for 24 h, and retained above 95% of its original activity after 4 months of storage at –80 ºC. The K values of XR for xylose and NADPH were 81.78 mM and 7.29 µM while the Vmaxm for xylose and NADPH were 178.57 and 12.5 µM/min, respectively. The high V max and low K values of XR for xylose reflecting a highly productive reaction among XR and xylose. Further, a sequential optimization based on OFAT approach and statistical program was followed to enhance xylitol production from xylose-rich MWSHH using XR. Firstly, the OFAT method coarsely evaluated the optimum levels of variables. Secondly, the significant variables for maximum xylitol production were screened out through fractional factorial design (FFD) to be reaction time, temperature and pH. Finally, the significant variables were fine-tuned by RSM and were found to be 12.25 h, 35 ºC and 6.5, respectively, giving the maximum xylitol yield and productivity of 86.57% and 1.33 g/L· h, respectively. Optimization of process conditions using sequential strategies resulted in 1.55-fold improvement in overall xylitol synthesis. This study developed a novel reaction medium to improve xylitol production to a considerable level using MWSHH. 2012-11 Thesis http://umpir.ump.edu.my/id/eprint/37083/ http://umpir.ump.edu.my/id/eprint/37083/1/SYNTHESIS%20OF%20XYLITOL%20FROM%20MERANTI%20WOOD%20SAWDUST%20IN%20BATCH.pdf pdf en public phd doctoral Universiti Malaysia Pahang Faculty of Chemical & Natural Resources Engineering Mimi Sakinah, Abdul Munaim
institution	Universiti Malaysia Pahang Al-Sultan Abdullah
collection	UMPSA Institutional Repository
language	English
advisor	Mimi Sakinah, Abdul Munaim
topic	TP Chemical technology
spellingShingle	TP Chemical technology Islam, S. M. Rafiqul Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase
description	The microbial production of xylitol has been studied extensively as an alternative to the chemical process, which on an industrial-scale is time-consuming mainly due to sterilization, inoculum development and product recovery problem. Apart from using pure xylose, no other substrate has been proposed for xylitol synthesis using xylose reductase (XR). The aim of this study was to synthesize xylitol, a specialty product, from Meranti wood sawdust hemicellulosic hydrolysate (MWSHH) by locally produced XR. MWS is a sawmill waste, which can be a promising source of xylose for xylitol production. The kinetic parameters of mathematical models were determined to predict xylose, glucose, furfural, and acetic acid concentration in the hydrolysate. Optimization of MWS hydrolysis was conducted with statistical design including onefactor-at-a-time (OFAT) method for maximum xylose recovery. The results of OFAT indicated the residence time, temperature, and acid concentration to be the major factors improving xylose recovery with a value of 60 min, 125 ºC, and 4%, respectively. These factors were further optimized by response surface methodology (RSM), and the optimum values obtained were 80 min, 124 ºC, and 3.26%, respectively. Under these conditions xylose yield and selectivity were attained at 90.6% and 4.05 g/g, respectively. XR was isolated from adapted C. tropicalis and characterized. The activity of NADPH-dependent XR measured was 11.16 U/mL. It was stable at pH 5.0–7.0 and temperature of 25–40 ºC for 24 h, and retained above 95% of its original activity after 4 months of storage at –80 ºC. The K values of XR for xylose and NADPH were 81.78 mM and 7.29 µM while the Vmaxm for xylose and NADPH were 178.57 and 12.5 µM/min, respectively. The high V max and low K values of XR for xylose reflecting a highly productive reaction among XR and xylose. Further, a sequential optimization based on OFAT approach and statistical program was followed to enhance xylitol production from xylose-rich MWSHH using XR. Firstly, the OFAT method coarsely evaluated the optimum levels of variables. Secondly, the significant variables for maximum xylitol production were screened out through fractional factorial design (FFD) to be reaction time, temperature and pH. Finally, the significant variables were fine-tuned by RSM and were found to be 12.25 h, 35 ºC and 6.5, respectively, giving the maximum xylitol yield and productivity of 86.57% and 1.33 g/L· h, respectively. Optimization of process conditions using sequential strategies resulted in 1.55-fold improvement in overall xylitol synthesis. This study developed a novel reaction medium to improve xylitol production to a considerable level using MWSHH.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Islam, S. M. Rafiqul
author_facet	Islam, S. M. Rafiqul
author_sort	Islam, S. M. Rafiqul
title	Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase
title_short	Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase
title_full	Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase
title_fullStr	Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase
title_full_unstemmed	Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase
title_sort	synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase
granting_institution	Universiti Malaysia Pahang
granting_department	Faculty of Chemical & Natural Resources Engineering
publishDate	2012
url	http://umpir.ump.edu.my/id/eprint/37083/1/SYNTHESIS%20OF%20XYLITOL%20FROM%20MERANTI%20WOOD%20SAWDUST%20IN%20BATCH.pdf
_version_	1783732261539020800

Synthesis of xylitol from meranti wood sawdust in batch process by locally produced xylose reductase

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