Structural investigations on green culms and charcoal of Bambusa multiplex.

Green culms of Bambusa multiplex and the bamboo charcoal carbonized from the green culms at 700°C have been studied by means of X-ray diffraction, X-ray fluorescent element analysis, analytical scanning electron microscopy, and analytical scanning transmission electron microscopy (STEM), aiming at industrial applications as raw materials for functional devices and substances. It is revealed that the green culms and the charcoal contain a significant amount of Si, in particular, ∼18 wt % in the skin. The green culms comprise amorphous and crystalline celluloses. The charcoal has a so-called amorphous structure which is composed of randomly distributed carbon nanotubes and fibers. The growth of Ag-doped activated charcoal powders that were produced by two different methods using this charcoal powder has also been studied.

Asymmetric flexural behavior from bamboo's functionally graded hierarchical structure: underlying mechanisms.

As one of the most renewable resources on Earth, bamboo has recently attracted increasing interest for its promising applications in sustainable structural purposes. Its superior mechanical properties arising from the unique functionally-graded (FG) hierarchical structure also make bamboo an excellent candidate for bio-mimicking purposes in advanced material design. However, despite its well-documented, impressive mechanical characteristics, the intriguing asymmetry in flexural behavior of bamboo, alongside its underlying mechanisms, has not yet been fully understood. Here, we used multi-scale mechanical characterizations assisted with advanced environmental scanning electron microscopy (ESEM) to investigate the asymmetric flexural responses of natural bamboo (Phyllostachys edulis) strips under different loading configurations, during "elastic bending" and "fracture failure" stages, with their respective deformation mechanisms at microstructural level. Results showed that the gradient distribution of the vascular bundles along the thickness direction is mainly responsible for the exhibited asymmetry, whereas the hierarchical fiber/parenchyma cellular structure plays a critical role in alternating the dominant factors for determining the distinctly different failure mechanisms. A numerical model has been likewise adopted to validate the effective flexural moduli of bamboo strips as a function of their FG parameters, while additional experiments on uniaxial loading of bamboo specimens were performed to assess the tension-compression asymmetry, for further understanding of the microstructure evolution of bamboo's outer and innermost layers under different bending states. This work could provide insights to help the processing of novel bamboo-based composites and enable the bio-inspired design of advanced structural materials with desired flexural behavior.

Enhanced adsorption of perfluorooctane sulfonate and perfluorooctanoate by bamboo-derived granular activated carbon.

A bamboo-derived granular activated carbon with large pores was successfully prepared by KOH activation, and used to remove perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from aqueous solution. The granular activated carbon prepared at the KOH/C mass ratio of 4 and activation temperature of 900°C had fast and high adsorption for PFOS and PFOA. Their adsorption equilibrium was achieved within 24h, which was attributed to their fast diffusion in the micron-sized pores of activated carbon. This granular activated carbon exhibited the maximum adsorbed amount of 2.32mmol/g for PFOS and 1.15mmol/g for PFOA at pH 5.0, much higher than other granular and powdered activated carbons reported. The activated carbon prepared under the severe activation condition contained many enlarged pores, favorable for the adsorption of PFOS and PFOA. In addition, the spent activated carbon was hardly regenerated in NaOH/NaCl solution, while the regeneration efficiency was significantly enhanced in hot water and methanol/ethanol solution, indicating that hydrophobic interaction was mainly responsible for the adsorption. The regeneration percent was up to 98% using 50% ethanol solution at 45°C.

Evaluation of aqueous ammonia pretreatment for enzymatic hydrolysis of different fractions of bamboo shoot and mature bamboo.

The production of fermentable sugars from different fractions of bamboo shoots and mature bamboos (Phyllostachys heterocycla var. pubescens) by cellulase and/or xylanase was investigated. Aqueous ammonia pretreatment exhibited high but different delignification capacities for different bamboo fractions. Supplementation of cellulases with xylanase synergistically improved the glucose and xylose yields of mature bamboo fractions. High hydrolyzability was observed in the hydrolysis of both non-pretreated and pretreated bamboo shoot fractions, suggesting pretreatment was not necessary for the hydrolysis of bamboo shoots. High hydrolyzability together with the advantages of low lignin content, fast growth, and widely distribution demonstrated that bamboo shoots were excellent lignocellulosic materials for the production of bioethanol and other biochemicals.

Plant material features responsible for bamboo's excellent mechanical performance: a comparison of tensile properties of bamboo and spruce at the tissue, fibre and cell wall levels.

BACKGROUND AND AIMS: Bamboo is well known for its fast growth and excellent mechanical performance, but the underlying relationships between its structure and properties are only partially known. Since it lacks secondary thickening, bamboo cannot use adaptive growth in the same way as a tree would in order to modify the geometry of the stem and increase its moment of inertia to cope with bending stresses caused by wind loads. Consequently, mechanical adaptation can only be achieved at the tissue level, and this study aims to examine how this is achieved by comparison with a softwood tree species at the tissue, fibre and cell wall levels. METHODS: The mechanical properties of single fibres and tissue slices of stems of mature moso bamboo (Phyllostachys pubescens) and spruce (Picea abies) latewood were investigated in microtensile tests. Cell parameters, cellulose microfibril angles and chemical composition were determined using light and electron microscopy, wide-angle X-ray scattering and confocal Raman microscopy. KEY RESULTS: Pronounced differences in tensile stiffness and strength were found at the tissue and fibre levels, but not at the cell wall level. Thus, under tensile loads, the differing wall structures of bamboo (multilayered) and spruce (sandwich-like) appear to be of minor relevance. CONCLUSIONS: The superior tensile properties of bamboo fibres and fibre bundles are mainly a result of amplified cell wall formation, leading to a densely packed tissue, rather than being based on specific cell wall properties. The material optimization towards extremely compact fibres with a multi-lamellar cell wall in bamboo might be a result of a plant growth strategy that compensates for the lack of secondary thickening growth at the tissue level, which is not only favourable for the biomechanics of the plant but is also increasingly utilized in terms of engineering products made from bamboo culms.

Enhanced enzymatic hydrolysis of bamboo (Dendrocalamus giganteus Munro) culm by hydrothermal pretreatment.

Bamboo was non-isothermally pretreated with hot water at 140-200°C for different times (10-120 min). The effects of pretreatment conditions on the degradation of carbohydrates, cellulose crystallinity, partial removal/relocation of lignin, morphologic change of the feedstock, and glucose yield during the enzymatic hydrolysis were investigated. The effective removal of amorphous cellulose and hemicelluloses led to the increase of crystalline index of the residues. In comparison with the raw material, the surface of the pretreated samples was irregular and numerous lignin droplets appeared on the cellulose bundle surface under the intense pretreatment conditions. The glucose conversion increased with the raise of pretreatment temperature and the prolongation of time, and the maximum conversion of 75.7% was achieved for the sample pretreated at 200°C for 120 min, whereas the untreated sample was only 15.7%. The result illustrated that hydrothermal pretreatment affected the composition of bamboo, and remarkably enhanced the enzymatic hydrolysis efficiency.

Surface characterizations of bamboo substrates treated by hot water extraction.

Environment Scanning Electron Microscopy (ESEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface morphology and chemical changes on both the interior and exterior surface of bamboo (Dendrocalamopsis oldhami) substrates treated by hot water extraction. ESEM results showed the visible changes between exterior and interior surface of the treated substrates, in where spherical droplets did not extensively appear on both the surfaces at start of the pretreatment; nevertheless the droplets formation on the exterior surface occurred more rapidly than that of the interior surface. Results from XPS examination that the increase of C1 (C-C, C-H) concentration and decrease of O/C ratio and O1 (C=O) concentration of the samples on the both surfaces further demonstrated that both surfaces consisted of increasing amount of lignin as the extraction continued, especially for exterior surface. The O/C ratios finally reached to a level-off value with exterior surface 0.34 and interior surface 0.37.

Effects of elevated CO2 and temperature on photosynthesis and leaf traits of an understory dwarf bamboo in subalpine forest zone, China.

The dwarf bamboo (Fargesia rufa Yi), growing understory in subalpine dark coniferous forest, is one of the main foods for giant panda, and it influences the regeneration of subalpine coniferous forests in southwestern China. To investigate the effects of elevated CO2, temperature and their combination, the dwarf bamboo plantlets were exposed to two CO2 regimes (ambient and double ambient CO2 concentration) and two temperatures (ambient and +2.2°C) in growth chambers. Gas exchange, leaf traits and carbohydrates concentration were measured after the 150-day experiment. Elevated CO2 significantly increased the net photosynthetic rate (Anet ), intrinsic water-use efficiency (WUEi ) and carbon isotope composition (δ¹³C) and decreased stomatal conductance (g(s)) and total chlorophyll concentration based on mass (Chl(m)) and area (Chl(a)). On the other hand, elevated CO2 decreased specific leaf area (SLA), which was increased by elevated temperature. Elevated CO2 also increased foliar carbon concentration based on mass (C(m)) and area (C(a)), nitrogen concentration based on area (N(a)), carbohydrates concentration (i.e. sucrose, sugar, starch and non-structural carbohydrates) and the slope of the A(net)-N(a) relationship. However, elevated temperature decreased C(m), C(a) and N(a). The combination of elevated CO2 and temperature hardly affected SLA, C(m), C(a), N(m), N(a), Chl(m) and Chl(a). Variables Anet and Na had positive linear relationships in all treatments. Our results showed that photosynthetic acclimation did not occur in dwarf bamboo at elevated CO2 and it could adjust physiology and morphology to enable the capture of more light, to increase WUE and improve nutritional conditions.

Holocellulase activity from Schizophyllum commune grown on bamboo: a comparison with different substrates.

The natural biodiversity that is found in tropical areas offers countless biotechnological opportunities; especially if we take in account that many biomolecules from several microorganisms have supported for many years, different industrial applications in areas such as pharmacology, agro-industry, bioprocess, environmental technology, and bioconversion. In order to find new lignocellulolytic enzymes and evaluate bamboo fibers as substrate, Schizophyllum commune a fungus with broad distribution was isolated and grown during 15 days in liquid culture medium containing 1% lignocellulosic fibers from bamboo, banana stem, and sugarcane bagasse. The enzymatic activity of xylanase, mannanase, polygalacturonase, CMCase, FPase, and avicelase were evaluated. Sugarcane bagasse and banana stem showed to induce higher hollocellulase activity when compared with bamboo as the main carbon source. The physical mechanism that the fungus uses to degrade bamboo was observed not only in fibers naturally infected but also in healthy fibers that were treated and untreated with enzyme solution. SEM analysis showed the structural disruption and invasion of the vascular bundles, parenchyma cells, and parenchymatous tissues as a consequence of the presence of this fungus and the catalytic action of its enzymes into the plant tissue.

Mechanical properties of functionally graded hierarchical bamboo structures.

This paper presents the results of a series of multi-scale experiments and numerical models concerning the mechanical properties of moso culm functionally graded bamboo structures. On the nano- and microscales, nanoindentation techniques are used to study the local variations in the Young's moduli of moso culm bamboo cross-sections. These are then incorporated into finite element models in which the actual variations in Young's moduli are used to model the deformation and fracture of bamboo during fracture toughness experiments. Similarly, the measured gradations in moduli are incorporated into crack bridging models that predict the toughening observed during resistance curve tests. The implications of the results are discussed for the bio-inspired design of structures that mimic the layered, functionally graded structure of bamboo.