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Conversion of rice husks to polyhydroxyalkanoates (PHA) via a three-step process : optimized alkaline pretreatment, enzymatic hydrolysis, and biosynthesis by Burkholderia cepacia USM (JCM 15050)

Heng, King Sern; Hatti-Kaul, Rajni LU ; Adam, Farook; Fukui, Toshiaki and Sudesh, Kumar (2017) In Journal of Chemical Technology and Biotechnology 92(1). p.100-108
Abstract

BACKGROUND: Rice husks (RH) are agricultural residues with abundant storage of cellulose and hemicellulose, making them a potential feedstock for polyhydroxyalkanoate (PHA) production. In this study, optimization of pretreatment with alkali under various conditions was performed before enzymatic hydrolysis using Celluclast 1.5 L (EC 3.2.1.4) and Novozyme 188 (EC 3.2.1.21). The hydrolysate was fed to two strains, Burkholderia cepacia USM (JCM 15050) and Cupriavidus necator NSDG-GG, an engineered strain of Cupriavidus necator H16, to evaluate their PHA production. RESULTS: Pretreatment of RH using 1.0 mol L−1 potassium hydroxide (KOH) at high temperature and pressure (HTP) (121 °C, 0.1 MPa) gave maximum sugar yield of up to 87%... (More)

BACKGROUND: Rice husks (RH) are agricultural residues with abundant storage of cellulose and hemicellulose, making them a potential feedstock for polyhydroxyalkanoate (PHA) production. In this study, optimization of pretreatment with alkali under various conditions was performed before enzymatic hydrolysis using Celluclast 1.5 L (EC 3.2.1.4) and Novozyme 188 (EC 3.2.1.21). The hydrolysate was fed to two strains, Burkholderia cepacia USM (JCM 15050) and Cupriavidus necator NSDG-GG, an engineered strain of Cupriavidus necator H16, to evaluate their PHA production. RESULTS: Pretreatment of RH using 1.0 mol L−1 potassium hydroxide (KOH) at high temperature and pressure (HTP) (121 °C, 0.1 MPa) gave maximum sugar yield of up to 87% (per total carbohydrate content) after optimized enzymatic hydrolysis, whereby the undiluted hydrolysate contained approximately 20 g L−1 total reducing sugars (TRS). B. cepacia USM utilized the hydrolysate more efficiently compared with C. necator NSDG-GG, with a maximum cell dry weight (CDW) of 4.9 g L−1 and 40 wt% PHA at shake-flask scale. The CDW and PHA content of B. cepacia USM cultivated in a 5 L fermentor were 7.8 g L−1 and 50%, respectively. The decrease in total phenolics at the end of fermentation suggested that B. cepacia USM was able to metabolize phenolic compounds. CONCLUSION: Through optimized alkali pretreatment and enzymatic hydrolysis, RH has the potential to be converted to PHA by B. cepacia USM, thus valorizing this agricultural by-product. © 2016 Society of Chemical Industry.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
alkali pretreatment, Burkholderia cepacia, polyhydroxyalkanoate, rice husks
in
Journal of Chemical Technology and Biotechnology
volume
92
issue
1
pages
9 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:84999766525
  • wos:000389443600012
ISSN
0268-2575
DOI
10.1002/jctb.4993
language
English
LU publication?
yes
id
cd6c2a98-28de-4870-841a-945a53f7e479
date added to LUP
2017-03-21 15:28:04
date last changed
2017-09-18 11:33:31
@article{cd6c2a98-28de-4870-841a-945a53f7e479,
  abstract     = {<p>BACKGROUND: Rice husks (RH) are agricultural residues with abundant storage of cellulose and hemicellulose, making them a potential feedstock for polyhydroxyalkanoate (PHA) production. In this study, optimization of pretreatment with alkali under various conditions was performed before enzymatic hydrolysis using Celluclast 1.5 L (EC 3.2.1.4) and Novozyme 188 (EC 3.2.1.21). The hydrolysate was fed to two strains, Burkholderia cepacia USM (JCM 15050) and Cupriavidus necator NSDG-GG, an engineered strain of Cupriavidus necator H16, to evaluate their PHA production. RESULTS: Pretreatment of RH using 1.0 mol L<sup>−1</sup> potassium hydroxide (KOH) at high temperature and pressure (HTP) (121 °C, 0.1 MPa) gave maximum sugar yield of up to 87% (per total carbohydrate content) after optimized enzymatic hydrolysis, whereby the undiluted hydrolysate contained approximately 20 g L<sup>−1</sup> total reducing sugars (TRS). B. cepacia USM utilized the hydrolysate more efficiently compared with C. necator NSDG-GG, with a maximum cell dry weight (CDW) of 4.9 g L<sup>−1</sup> and 40 wt% PHA at shake-flask scale. The CDW and PHA content of B. cepacia USM cultivated in a 5 L fermentor were 7.8 g L<sup>−1</sup> and 50%, respectively. The decrease in total phenolics at the end of fermentation suggested that B. cepacia USM was able to metabolize phenolic compounds. CONCLUSION: Through optimized alkali pretreatment and enzymatic hydrolysis, RH has the potential to be converted to PHA by B. cepacia USM, thus valorizing this agricultural by-product. © 2016 Society of Chemical Industry.</p>},
  author       = {Heng, King Sern and Hatti-Kaul, Rajni and Adam, Farook and Fukui, Toshiaki and Sudesh, Kumar},
  issn         = {0268-2575},
  keyword      = {alkali pretreatment,Burkholderia cepacia,polyhydroxyalkanoate,rice husks},
  language     = {eng},
  month        = {01},
  number       = {1},
  pages        = {100--108},
  publisher    = {Wiley-Blackwell},
  series       = {Journal of Chemical Technology and Biotechnology},
  title        = {Conversion of rice husks to polyhydroxyalkanoates (PHA) via a three-step process : optimized alkaline pretreatment, enzymatic hydrolysis, and biosynthesis by Burkholderia cepacia USM (JCM 15050)},
  url          = {http://dx.doi.org/10.1002/jctb.4993},
  volume       = {92},
  year         = {2017},
}