Armando G. McDonald

Polyhydroxybutyrate synthesis on biodiesel wastewater using mixed microbial consortia.

Crude glycerol (CG), a by-product of biodiesel production, is an organic carbon-rich substrate with potential as feedstock for polyhydroxyalkanoate (PHA) production. PHA is a biodegradable thermoplastic synthesized by microorganisms as an intracellular granule. In this study we investigated PHA production on CG using mixed microbial consortia (MMC) and determined that the enriched MMC produced exclusively polyhydroxybutyrate (PHB) utilizing the methanol fraction. PHB synthesis appeared to be stimulated by a macronutrient deficiency. Intracellular concentrations remained relatively constant over an operational cycle, with microbial growth occurring concurrent with polymer synthesis. PHB average molecular weights ranged from 200-380 kDa, while thermal properties compared well with commercial PHB. The resulting PHB material properties and characteristics would be suitable for many commercial uses. Considering full-scale process application, it was estimated that a 38 million L (10 million gallon) per year biodiesel operation could potentially produce up to 19 metric ton (20.9t on) of PHB per year.

Structures of the O chains from lipopolysaccharides of Campylobacter jejuni serotypes O:23 and O:36

Lipopolysaccharides of C. jejuni serotypes O:23 and O:36 have been shown to contain structurally variable O polysaccharide chains with repeating units of four closely-related types: ----3)-beta-D-GlcpNAc-(1----3)-alpha-D-Galp-(1----2)-6d-alpha-D-alt-H epp-(1---- , ----3)-beta-D-GlcpNAc-(1----3)-alpha-D-Galp-(1----2)-6d-3-Me-alpha-D-alt -Hepp- (1----, ----3)-beta-D-GlcpNAc-(1----3)-alpha-D-Galp-(1----2)-D-glycero-alpha-D-a lt-Hepp - (1----, and ----3)-beta-D-GlcpNAc-(1----3)-alpha-D-Galp-(1----2)-3-Me-D-glycero-alph a-D-alt - Hepp-(1----. Structural methods included 1H- and 13C-NMR spectroscopy, methylation linkage analysis, fast atom bombardment mass spectrometry of methylated glycans, and selective fragmentations by the Smith degradation and N-deacetylation-nitrous acid deamination.

Cell differentiation, secondary cell-wall formation and transformation of callus tissue of Pinus radiata D. Don

Tracheid and sclereid differentiation was induced in callus cultures of Pinus radiata D. Don by culturing on a basal medium containing activated charcoal but no phytohormones; sclereids differentiated in callus derived from xylem strips, but not in callus derived from hypocotyl segments. The tracheids differentiated in hypocotyl-derived callus had helical, scalariform, reticulated or pitted secondary cell-wall patterns, but those differentiated in xylem-derived callus had a reticulate or pitted pattern. The thickened tracheid and sclereid walls contained lignin as indicated by the red colour reaction given with phloroglucinol–HCl. The presence of lignin in the cell walls of differentiated callus was confirmed using pyrolysis gas chromatography–mass spectrometry by the detection of phenylpropanoid components derived from lignin. Lignin was also detected using solid-state 13C cross-polarisation/magic-angle spinning nuclear magnetic resonance spectroscopy and quantified as thioglycolic acid lignin. Monosaccharide analyses of the cell walls isolated from differentiated and undifferentiated calli showed that the cell walls of the differentiated calli contained higher proportions of glucose and mannose, consistent with the presence of greater proportions of gluco- and/or galactogluco-mannans in the secondary cell walls of the differentiated cells. A protocol for the stable transformation of undifferentiated, xylem-derived cultures was successfully developed. Transgenic cell lines were established following Biolistic particle bombardment with a plasmid containing the coding region of the nptII gene and the coding region of the cad gene from P. radiata. Expression of the nptII gene in transgenic lines was confirmed by an NPTII–enzyme-linked immunosorbent assay. The overexpression of cad in the transgenic lines resulted in a down-regulation of cinnamyl alcohol dehydrogenase (EC 1.1.1.195) expression.

Grafting of Bacterial Polyhydroxybutyrate (PHB) onto Cellulose via In Situ Reactive Extrusion with Dicumyl Peroxide

Polyhydroxybutyrate (PHB) was grafted onto cellulose fiber by dicumyl peroxide (DCP) radical initiation via in situ reactive extrusion. The yield of the grafted (cellulose-g-PHB) copolymer was recorded and grafting efficiency was found to be dependent on the reaction time and DCP concentration. The grafting mechanism was investigated by electron spin resonance (ESR) analysis and showed the presence of radicals produced by DCP radical initiation. The grafted copolymer structure was determined by nuclear magnetic resonance (NMR) spectroscopy. Scanning electronic microscopy (SEM) showed that the cellulose-g-PHB copolymer formed a continuous phase between the surfaces of cellulose and PHB as compared to cellulose-PHB blends. The relative crystallinity of cellulose and PHB were quantified from Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) results, while the absolute degree of crystallinity was evaluated by differential scanning calorimetry (DSC). The reduction of crystallinity indicated the grafting reaction occurred not just in the amorphous region but also slightly in crystalline regions of both cellulose and PHB. The smaller crystal sizes suggested the brittleness of PHB was decreased. Thermogravimetric analysis (TGA) showed that the grafted copolymer was stabilized relative to PHB. By varying the reaction parameters the compositions (%PHB and %cellulose) of resultant cellulose-g-PHB copolymer are expected to be manipulated to obtain tunable properties.

Chemical and thermal characterization of potato peel waste and its fermentation residue as potential resources for biofuel and bioproducts production.

The growing demand for renewable fuels has driven the interest in the utilization of alternative waste materials such as potato peel waste (PPW) which contains fermentable carbohydrate. Fermentation of PPW using a mixed microbial consortium yielded about 60% unreacted PPW fermentation residue (PPW-FR). The PPW and PPW-FR were characterized by a combination of Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, gas chromatography-mass spectrometry (GC-MS), and thermogravimetric analysis (TGA) to quantify changes after fermentation. Fermentation of PPW resulted in fermentation of starch and concentrating lignin plus suberin and lipids in PPW-FR. TGA analysis showed that decomposition peaks differed for PPW (423 °C) and PPW-FR (457 °C). Pyrolysis-GC/MS showed an increase in phenolic and long chain fatty acid compounds with a concomitant decrease in carbohydrate derived compounds in the PPW after fermentation. Both the PPW and PPW-FR have shown potential based on properties to be converted into crude biofuel via thermochemical processes.

The chemical nature of kiln brown stain in radiata pine

Summary This paper presents results of a study on the chemical nature of kiln brown stain (KBS) that develops in kiln dried radiata pine (Pinus radiata D. Don) sapwood. KBS is a chocolate brown discolouration which develops approximately 0.5 mm under the timber surface. Stain free radiata pine was achieved during drying trials on “green” radiata pine sapwood which had been treated to extensive cold and hot water extraction. Differences in chemical composition between the sap and hot water extract were observed. Chemical analyses (of the water-soluble extracts) by a combination of chromatographic and spectroscopic techniques, demonstrated that carbohydrates, cyclitols, amino acids, protein, and phenolics were the main compound classes present. The presence of reducing sugars (glucose and fructose) and amino acids (glutamic acid) in the sap and hot water extracts support the theory that Amadori-Maillard type reactions significantly contribute to the formation of colour in KBS. Furthermore, lignin was also detected and is suspected to contribute to KBS formation. The relative contributions of colour formation to KBS intensity from either phenolics or Maillard-Amadori mechanisms is unknown.

Interfacial improvements in biocomposites based on poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) bioplastics reinforced and grafted with α-cellulose fibers

In this study, α-cellulose fibers reinforced green biocomposites based on polyhydroxybutyrate (PHB) and the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were prepared and characterized. The α-cellulose fibers were isolated from at-risk intermountain lodgepole pine wood by successive removal of extractives, lignin and hemicellulose. Grafting of PHB or PHBV onto cellulose was conducted using reactive extrusion with dicumyl peroxide free radical initiation at high temperature. It is postulated that the grafted copolymers at the interfaces of cellulose and the polymer matrix performed as an interfacial coupling agent. Grafting tended to interact with both the hydrophilic fibers and the hydrophobic PHB or PHBV matrix. The biocomposites were characterized by scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) and indicated good interfacial bonding and compatibility between the two phases. The mechanical properties of the biocomposites were improved by grafting due to improved stress transfer between the two interphases of the fiber/polymer matrix as compared to the blend control composite. The crystallinity of PHB, PHBV and cellulose in the biocomposite were reduced as determined by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) analyses. This in situ reactive extrusion process offers an effective approach to improve the properties of biocomposite materials from sustainable resources.

Lactic acid production with undefined mixed culture fermentation of potato peel waste

Potato peel waste (PPW) as zero value byproduct generated from food processing plant contains a large quantity of starch, non-starch polysaccharide, lignin, protein, and lipid. PPW as one promising carbon source can be managed and utilized to value added bioproducts through a simple fermentation process using undefined mixed cultures inoculated from wastewater treatment plant sludge. A series of non-pH controlled batch fermentations under different conditions such as pretreatment process, enzymatic hydrolysis, temperature, and solids loading were studied. Lactic acid (LA) was the major product, followed by acetic acid (AA) and ethanol under fermentation conditions without the presence of added hydrolytic enzymes. The maximum yields of LA, AA, and ethanol were respectively, 0.22 g g(-1), 0.06 g g(-1), and 0.05 g g(-1). The highest LA concentration of 14.7 g L(-1) was obtained from a bioreactor with initial solids loading of 60 g L(-1) at 35°C.

A Review on Grafting of Biofibers for Biocomposites

A recent increase in the use of biofibers as low-cost and renewable reinforcement for the polymer biocomposites has been seen globally. Biofibers are classified into: lignocellulosic fibers (i.e., cellulose, wood and natural fibers), nanocellulose (i.e., cellulose nanocrystals and cellulose nanofibrils), and bacterial cellulose, while polymer matrix materials can be petroleum based or bio-based. Green biocomposites can be produced using both biobased fibers and polymers. Incompatibility between the hydrophilic biofibers and hydrophobic polymer matrix can cause performance failure of resulting biocomposites. Diverse efforts have focused on the modification of biofibers in order to improve the performances of biocomposites. “Grafting” copolymerization strategy can render the advantages of biofiber and impart polymer properties onto it and the performance of biocomposites can be tuned through changing grafting parameters. This review presents a short overview of various “grafting” methods which can be directly or potentially employed to enhance the interaction between biofibers and a polymer matrix for biocomposites. Major grafting techniques, including ring opening polymerization, grafting via coupling agent and free radical induced grafting, have been discussed. Improved properties such as mechanical, thermal, and water resistance have provided grafted biocomposites with new opportunities for applications in specific industries.

Analysis of DCM extractable components from hot-pressed hybrid poplar

Abstract The effects of thermal compression on the organic-soluble material of a uniform wood substrate, hybrid poplar (clone OP-367), has been studied. Poplar veneers were preconditioned to 0% or 8% moisture content and subsequently hot pressed at 150°C, 200°C, and 250°C. The dichloromethane (DCM) extracts were characterized by various hyphenated analyses [gas chromatography-mass spectrometry (GC-MS), analytical pyrolysis (Py-GC-MS), electrospray ionization-mass spectrometry (ESI-MS), and gel permeation chromatography (GPC)]. The yields and composition of extractable compounds were markedly influenced by treatment at 250°C compared to those obtained at lower temperatures. Most importantly, the organic extracts contained a significant portion of lignin-derived compounds after treatment at 250°C.