Softwood hydrolysate as a carbon source for polyhydroxyalkanoate production

Abstract

BACKGROUND: Forest biomass represents a potential low-cost feedstock for polyhydroxyalkanoate (PHA) production. Softwoods, such as Pinus radiata (D.Don) are difficult to digest and require special pretreatments to expose polysaccharides for enzymatic saccharification. Different pretreatments can lead to inhibitor formation that may adversely affect PHA synthesis. RESULTS:Pinus radiata wood chips were subjected to high-temperature mechanical pre-treatment (HTMP) or steam explosion in the presence of sulphur dioxide (SEW) before being enzymatically treated to produce corresponding hydrolysates. Two PHA-producing bacteria Novosphingobium nitrogenifigens Y88 T and Sphingobium scionense WP01 T were grown on these hydrolysates. The highest content of PHA was produced by WP01 grown on HTMP hydrolysate (32% w/w PHA, Y PHA/glucose = 0.22 and theoretical maximum yield of 46%). Gas chromatography and proton nuclear magnetic resonance spectroscopy indicated that the PHA produced was made up of polyhydroxybutyrate (PHB) with molecular weights ranging from 50-1600 kDa and polydispersities between 4.6 and 8.4. The melting temperature was close to that of pure PHB with percentage crystallinity ranging from 44-64%. CONCLUSION: This is the first report on the production of PHA from softwood hydrolysates derived from enzymatically saccharified pretreated Pinus radiata pulps. PHA characterizationPolymer composition analysed by GC showed that the PHA produced was exclusively made up of PHB, irrespective of microbial strain and carbon source. Proton NMR spectra of the isolated PHA polymer confirmed that different PHA samples are exclusively made up of PHB ≥ 95% w/w. A representative 1 H NMR spectrum of best case PHA produced from strain wileyonlinelibrary.com/jctb

Use of Lignocellulosic Materials for PHA Production

“…Two PHB-producing bacteria Novosphingobium nitrogenifigens and Sphingobium scionense were grown on these hydrolysates. The highest PHB yields (dry biomass concentration 1.23 g L -1 , PHB content in biomass 32 % and PHB yield 0.4 g L -1 ) were observed in Sphingobium scionense 40 . Furthermore, Silva et al tested PHAs production employing Brevundimonas vesicularis and Sphingopyxis macrogoltabida using acid-hydrolysed sawdust as a carbon source.…”

Strength of adsorption of polyethylene glycol on pretreated Pinus radiata wood and consequences for enzymatic saccharification

“…Pine wood chips were obtained from a local sawmill and were pretreated with steam at 170 C for 72 min without addition of chemicals, then converted to pulp in a single disk refiner at Scion's fibre and pulp processing pilot plant [25]. The composition of the pulp (w w À1 ) was as follows: lignin 34.5%, glucan 51.5%, xylan 4.1%, mannan 6.4%, galactan 1.0%, arabinan 0.2% and extractives 1.8%.…”

Production of Polyhydroxyalkanoates Using Hydrolyzates of Spruce Sawdust: Comparison of Hydrolyzates Detoxification by Application of Overliming, Active Carbon, and Lignite

“…Further, Bowers et al studied PHA production wood chips of Pinus radiata which were subjected to high-temperature mechanical pre-treatment or steam explosion in the presence of sulphur dioxide before being enzymatically hydrolyzed. Novosphingobium nitrogenifigens and Sphingobium scionense were used for PHA production on these hydrolyzates [ 9 ]. Brevundimonas vesicularis and Sphingopyxis macrogoltabida were employed by Silva et al [ 10 ] to produce ter-polymer consisting of 3-hydroxybutyrate, 3-hydroxyvalerate, and lactic acid (3-hydroxypropionate) from acid hydrolyzed sawdust.…”