Decomposition of sugarcane bagasse with lignocellulose-derived thermotolerant and thermoresistant Penicillia and Aspergilli

To promote the decomposition of sugarcane bagasse (SCB) for conversion into value-added products and to reduce waste, the capability of fungal mixes (FMs) to degrade SCB was examined. A total of 169 isolates from SCB and non-SCB were categorized as thermotolerant and thermoresistant. Thirty-six fungal candidates were screened for the presence of polyphenol oxidase, endoglucanase (EDN) and xylanase (XLN) activities, and EDN and XLN activities were quantitated. Five identified isolates (Aspergillus flavus AG10; Aspergillus niger AG68 & NB23; and Penicillium citrinum AG93 & AG140) were selected as the best enzyme producers, and 15 moderately to highly xylolytic, cellulolytic and ligninolytic isolates were added to construct FMs. Using a Taguchi design, the top ten reducing sugar-producing FMs (no. 12 showed the maximum amount of reducing sugar, at 2.11 mg g⁻¹, followed by no. 7, 15, 2, 16, 11, 13, 6, 4, & 8) were selected as potential agents for decomposition durations of 1, 2 and 3 months. The maximum decrease in SCB materials compared with the control was generated by FM 6 (9.08% cellulose reduction); FM 13 (21.03% hemicellulose reduction); and FM 16 (9.21% lignin reduction). These results indicate the potential use of SCB as a substrate for synergistic FMs. These FMs could be applied to the large-scale composting of SCB and other related agricultural residues, thus improving the biological pretreatment of lignocellulose.     

Hydrolysis of newspaper polysaccharides under sulfate reducing and methane producing conditions

The initial decomposition rates of cellulose and hemicellulose were measured using toluene to specifically inhibit the microbial uptake of hydrolysis products during the degradation of newspaper under sulfate reducing and methane producing conditions. The amount of glucose and xylose accumulation in the first 2 weeks of incubation period was higher in the sulfate reducing condition compared to the methane producing condition. It was estimated that 28 and 6% of initially loaded cellulose in the sulfate reducing condition and the methane producing condition was hydrolyzed, respectively. Accordingly, the newspaper-cellulose hydrolysis rate constant was estimated to be 6.7 times higher in sulfate reducing condition than in methane producing condition. Based on the glucose accumulation patterns, when sulfate reducing bacteria (SRB) were inhibited by anthraquinone and molybdate (Na₂MoO₄), it may be suggested that SRB might have contributed to the hydrolysis of cellulose, while their effect on the hydrolysis of hemicellulose could not be elucidated.     

High quality draft genome sequence of Olivibacter sitiensis type strain (AW-6T), a diphenol degrader with genes involved in the catechol pathway

Olivibacter sitiensis Ntougias et al. 2007 is a member of the family Sphingobacteriaceae, phylum Bacteroidetes. Members of the genus Olivibacter are phylogenetically diverse and of significant interest. They occur in diverse habitats, such as rhizosphere and contaminated soils, viscous wastes, composts, biofilter clean-up facilities on contaminated sites and cave environments, and they are involved in the degradation of complex and toxic compounds. Here we describe the features of O. sitiensis AW-6^T, together with the permanent-draft genome sequence and annotation. The organism was sequenced under the Genomic Encyclopedia for Bacteria and Archaea (GEBA) project at the DOE Joint Genome Institute and is the first genome sequence of a species within the genus Olivibacter. The genome is 5,053,571 bp long and is comprised of 110 scaffolds with an average GC content of 44.61%. Of the 4,565 genes predicted, 4,501 were protein-coding genes and 64 were RNA genes. Most protein-coding genes (68.52%) were assigned to a putative function. The identification of 2-keto-4-pentenoate hydratase/2-oxohepta-3-ene-1,7-dioic acid hydratase-coding genes indicates involvement of this organism in the catechol catabolic pathway. In addition, genes encoding for β-1,4-xylanases and β-1,4-xylosidases reveal the xylanolytic action of O. sitiensis.     

Cell wall chemistry and tissue structure underlie shifts in material properties of a perennial kelp

Laminaria is an abundant kelp genus in temperate nearshore ecosystems that grows with a circannual ‘stop-start’ pattern. Species of Laminaria play important ecological roles in kelp forests worldwide and are harvested commercially as a source of food and valuable extracts. In order to evaluate seasonal differences in tissue properties and composition, we compared the material properties, histology and cell-wall composition of overwintering blades with newly synthesized, actively growing blades from Laminaria setchellii. We found that overwintering blades were fortified with a thicker cortex and increased cell wall investment, leading to increased material strength. Overwintering tissues were composed of higher proportions of cellulose and fucose-containing polysaccharides (i.e. FCSPs, fucoidans) than newly formed blades and were found to possess thicker cell walls, likely to withstand the waves of winter storms. Chemical cell wall profiling revealed that significant proportions of fucose were associated with cellulose, especially in overwintering tissues, confirming the association between cellulose and some fucose-containing polysaccharides. Changes in material properties during the resting phase may allow these kelps to retain their non-growing blades through several months of winter storms. The results of this study demonstrate how one species might regulate its material properties seasonally, and at the same time shed light on the mechanisms that might control the material properties of kelps in general.     

Widespread occurrence of a covalent linkage between xyloglucan and acidic polysaccharides in suspension-cultured angiosperm cells

* BACKGROUND AND AIMS: Covalent linkages between xyloglucan and rhamnogalacturonan-I (RG-I) have been reported in the primary cell walls of cultured Rosa cells and may contribute to wall architecture. This study investigated whether this chemical feature is general to angiosperms or whether Rosa is unusual. * METHODS: Xyloglucan was alkali-extracted from the walls of l-[1-3H]arabinose-fed suspension-cultured cells of Arabidopsis, sycamore, rose, tomato, spinach, maize and barley. The polysaccharide was precipitated with 50 % ethanol and subjected to anion-exchange chromatography in 8 m urea. Eluted fractions were Driselase-digested, yielding [3H]isoprimeverose (diagnostic of [3H]xyloglucan). The Arabidopsis cells were also fed [6-14C]glucuronic acid, and radiolabelled pectins were extracted with ammonium oxalate. * KEY RESULTS: [3H]Xyloglucan was detected in acidic (galacturonate-containing) as well as non-anionic polysaccharide fractions. The proportion of the [3H]isoprimeverose units that were in anionic fractions was: Arabidopsis, 45 %; sycamore, 60 %; rose, 44 %; tomato, 75 %; spinach, 70 %; maize, 50 %; barley, 70 %. In Arabidopsis cultures fed d-[6-(14)C]glucuronate, 20 % of the (galacturonate-14C)-labelled pectins were found to hydrogen-bond to cellulose, a characteristic normally restricted to hemicelluloses such as xyloglucan. * CONCLUSIONS: Alkali-stable, anionic complexes of xyloglucan (reported in the case of Rosa to be xyloglucan-RG-I covalent complexes) are widespread in the cell walls of angiosperms, including gramineous monocots.     

Auxin-induced changes in the cell wall structure: Changes in the sugar compositions, intrinsic viscosity and molecular weight distributions of matrix polysaccharides of the epicotyl cell wall of Vigna angularis

Rapid effects of indole-3-acetic acid (IAA) on the mechanical properties of cell wall, and sugar compositions, intrinsic viscosity and molecular weight distribution of cell wall polysaccharides were investigated with excised epicotyl segments of Vigna angularis Ohwi et Ohashi cv. Takara.

• 1 IAA caused cell wall loosening as studied by stress-relaxation analysis within 15 min after the IAA application.
• 2 IAA stimulated the decrease in the content of arabinose and galactose in the hemicellulose 1 h after its application. The amounts of other component sugars in the cell wall polysaccharides remained constant during the IAA-induced segment growth.
• 3 The intrinsic viscocity of the pectin increased as early as 30 min after the IAA application. This effect was not prevented when elongation growth of the segment was osmotically suppressed by 0.15 M mannitol.
• 4 Gel permeation chromatography of the pectin on a Sepharose 4 B column demonstrated that IAA caused increase in the mass-average molecular weight of the pectin. Analysis of the sugar compositions of the pectin eluted from the Sepharose 4 B column indicated that IAA increased the molecular weight of the polysaccharides composed of uronic acid, galactose, rhamnose and arabinose. This effect became apparent within 30 min after the IAA application. Furthermore, IAA increased the molecular weight of the pectin when elongation growth of the epicotyl segments was osmotically suppressed by 0.15 M mannitol.
• 5 Hemicellulose of the cell wall chromatographed on a Sepharose CL-4 B column. Analysis of the neutral sugar compositions and the iodine staining property (specific for xyloglucans) of the polysaccharide solution eluted from the column indicated that the hemicellulose consisted of xyloglucans, arabinogalactans and polysaccharides composed of xylose and/or mannose. IAA caused a decrease in the arabinogalactan content and depolymerization of xyloglucans. These IAA effects became apparent within 30 min after the IAA application. These changes occurred even when elongation growth of the epicotyl segments was osmotically suppressed by 0.15 M mannitol.

Polymerization of the pectin, degradation of arabinogalactans and depolymerization of xyloglucans appear to be involved in the mechanism by which IAA induces cell wall loosening and therefore extension growth of cells.     

Room temperature ionic liquids as emerging solvents for the pretreatment of lignocellulosic biomass

Room temperature ionic liquids (RTILs) are emerging as attractive and green solvents for lignocellulosic biomass pretreatment. The unique solvating properties of RTILs foster the disruption of the 3D network structure of lignin, cellulose, and hemicellulose, which allows high yields of fermentable sugars to be produced in subsequent enzymatic hydrolysis. In the current review, we summarize the physicochemical properties of RTILs that make them effective solvents for lignocellulose pretreatment including mechanisms of interaction between lignocellulosic biomass subcomponents and RTILs. We also highlight several recent strategies that exploit RTILs and generate high yields of fermentable sugars suitable for downstream biofuel production, and address new opportunities for use of lignocellulosic components, including lignin. Finally, we address some of the challenges that remain before large-scale use of RTILs may be achieved.     

Changes in apoplastic peroxidase activity and cell wall composition are associated with cold‐induced morpho‐anatomical plasticity of wheat leaves

• Temperate grasses, such as wheat, become compact plants with small thick leaves after exposure to low temperature. These responses are associated with cold hardiness, but their underlying mechanisms remain largely unknown. Here we analyse the effects of low temperature on leaf morpho‐anatomical structure, cell wall composition and activity of extracellular peroxidases, which play key roles in cell elongation and cell wall thickening, in two wheat cultivars with contrasting cold‐hardening ability.
• A combined microscopy and biochemical approach was applied to study actively growing leaves of winter (ProINTA‐Pincén) and spring (Buck‐Patacón) wheat developed under constant warm (25 °C) or cool (5 °C) temperature.
• Cold‐grown plants had shorter leaves but longer inter‐stomatal epidermal cells than warm‐grown plants. They had thicker walls in metaxylem vessels and mestome sheath cells, paralleled with accumulation of wall components, predominantly hemicellulose. These effects were more pronounced in the winter cultivar (Pincén). Cold also induced a sharp decrease in apoplastic peroxidase activity within the leaf elongating zone of Pincén, and a three‐fold increase in the distal mature zone of the leaf. This was consistent with the enhanced cell length and thicker cell walls in this cultivar at 5 °C.
• The different response to low temperature of apoplastic peroxidase activity and hemicellulose between leaf zones and cultivar types suggests they might play a central role in the development of cold‐induced compact morphology and cold hardening. New insights are presented on the potential temperature‐driven role of peroxidases and hemicellulose in cell wall dynamics of grasses.

     

Development of Multi-Component Transplant Mixes for Suppression of Meloidogyne incognita on Tomato (Lycopersicon esculentum)

The effects of combinations of organic amendments, phytochemicals, and plant-growth promoting rhizobacteria on tomato (Lycopersicon esculentum) germination, transplant growth, and infectivity of Meloidogyne incognita were evaluated. Two phytochemicals (citral and benzaldehyde), three organic amendments (pine bark, chitin, and hemicellulose), and three bacteria (Serratia marcescens, Brevibacterium iodinum, and Pseudomonas fluorescens) were assessed. Increasing rates of benzaldehyde and citral reduced nematode egg viability in vitro. Benzaldehyde was 100% efficacious as a nematicide against juveniles, whereas citral reduced juvenile viability to less than 20% at all rates tested. Benzaldehyde increased tomato seed germination and root weight, whereas citral decreased both. High rates of pine bark or chitin reduced plant growth but not seed germination, whereas low rates of chitin increased shoot length, shoot weight, and root weight; improved root condition; and reduced galling. The combination of chitin and benzaldehyde significantly improved tomato transplant growth and reduced galling. While each of the bacterial isolates contributed to increased plant growth in combination treatments, only Brevibacterium iodinum applied alone significantly improved plant growth.