ANALYSIS OF THE CHEMICAL COMPOSITION AND MORPHOLOGICAL STRUCTURE OF BANANA PSEUDO-STEM Kun Li,a Shiyu Fu,a* Huaiyu Zhan,a Yao Zhan,a and Lucian A. Lucia a,b
An analysis of the chemical composition and anatomical structure of
banana pudo-stem was carried out using Light Microscopy (LM),
Scanning Electron Microscopy (SEM), and Confocal Lar Scanning
Microscopy (CLSM). The chemical analysis indicated there is a high
holocellulo content and low lignin content in banana pudo-stem
compared with some other non-wood fiber resources. The results
demonstrate that the banana pudo-stem has potential value for
pulping. In addition, we report for the first time from using LM and CLSM
that banana stems posss a structure involving helicoidal fibers
parated by barrier films.
Keywords: Banana pudo-stem; Chemical analysis; Scanning Electron Microscopy (SEM); Light Microscopy (LM); Confocal Lar Scanning Microscopy (CLSM)
Contact information: State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640 China; b. Laboratory of Soft Materials & Green Chemistry, Department of Wood & Paper Science, North Carolina State University, Raleigh, North Carolina 27695-8005 USA; * Corresponding author. Tel: +86 20 87112453
E-mail address: shyfu@scut.edu (S.Fu)
INTRODUCTION
In recent years, people have placed a high emphasis on forest prervation and rational u of forestry and agricultural residues. This trend is mainly motivated and accelerated by the dilemma of an ever-increasing consumption of wood fiber-bad products relative to dwindling wood resources. Furthermore, the application of cellulo fibers has many advantages: it is environmentally sound, recyclable, and low in cost. In 2006, the annual global production of lignocellulosic fibers from crops was about 4 billion tons, of which 60% came from agriculture and 40% from the forest. In comparison, the annual world production of steel was around 0.7 billion tons, and plastic was about
闩的读音0.1 billion tons (Justiz-Smith et al. 2008).
In general, banana pudo-stem is an abundant natural resource in subtropical and tropical regions and has potential for providing profitable products such as manure (Ultra et al. 2005) and feed (Ulloa et al. 2004), which call for practical techniques and process to exploit this natural resource. In South China, the production of banana has significant economical importance. After harvesting banana bunches from the trees over a tract of land, a large amount of waste biomass remains, becau each banana plant cannot be ud for the next harvest. The bare pudo-stems are normally felled and usually abandoned in the soil plantation to become organic waste and cau environmental pollution. Therefore, exploitation of the waste banana pudo-stems will be significantly beneficial to the environment and bring additional profits to farmers.
It has been reported (Justiz-Smith et al. 2008) that the fiber of banana pudo-stem has a high Young’s modulus and water absorption capacity. Moreover, the banana pudo-stem shows satisfactory physical properties, such as relatively high tensile strength and stiffness, which indicate its prospect as a promising fiber material. The application of natural fibers including banana pudo-stem has been proved promising in various technical fields, such as replacing synthetic fibers as reinforcement in various composites ud in automobile parts (Pothan and Thomas (2003). Zainudin
青金石蓝(2009) studied the thermal behavior of banana pudo-stem (BPS)-filled unplastisized polyvinyl chloride (UPVC) composites. From the study, the thermal stability of the composites was found to be higher than that of BPS fiber and the UPVC matrix. Savastano (2004) studied the application of natural fiberous materials, including banana stem, as reinforcement in cement product. The results demonstrated that the narrow and recycled fibers possd irregular surfaces and low coarness; hence, they can be ud as cement reinforcement. Additionally, the fiber of banana pudo-stem has potential for u in absorbents becau of its strong water absorption property. Anirudhan (2006) and Noeline (2005) studied new absorbent systems containing banana pudo-stem. The absorbent systems, which can remove phosphate from wastewater, exhibit high absorption potential and satisfactory recyclability.
Some other valuable products can also be obtained from banana pudo-stem. For example, the high content of cellulo in banana pudo-stem has promising potential as a source of man-modified polysaccharide. Adinugraha (2005) studied the synthesis of sodium carboxymethylcellulsoe (CMC) from Cavendish banana pudo-stem and succeeded in establishing a novel method to utilize Cavendish banana pudo-stem for preparing sodium CMC. Additionally, Wuyts (2006) succeeded in extracting ployphenol oxida (PPO), which is a copper-containing enzyme with molecular oxygen as co-substrate.视觉游戏
People have long studied the application of banana pudo-stem in the pulping and papermaking industry. Guha (1960) studied the kraft pulping process of banana pudo-stem. Subrahmanyan (1963) drew the conclusion that the fiber of banana pudo-stem is higher in strength properties than areca husk by comparing their soda pulps. Heikal (1976) developed the nitric acid pulping process of banana pudo-stem. Dhake (1983) succeeded in producing high-yield chemi-mecahnical pulp of banana pudo-stem with pretreatment of NaOH. Cordeiro (2003) determined parts of the chemical compositions of banana pudo-stem and developed the soda-AQ pulping process of banana pudo-stem. Jahan (2007) studied the formic acid pulping and Totally Chlorine Free (TCF) bleaching of banana pudo-stem. Manimaran (2007) studied the biobleaching of banana pudo-stem with xylana. Cordeiro studied the microstructure of the banana pudo-stem fiber bundles (2005) and poly-bad composites (2006) with SEM and TEM. In this paper, more detailed morphological information of banana stem including pudo-stem and pith is provided by CLSM obrvation for the first time.
Further study on the chemical composition and microstructure of banana pudo-stem will be beneficial to the novel applications of this valuable resource. Therefore, the purpo of this paper is to determine the chemical composition and get detailed morphological information of banana pudo-stem with variety of measurements.
EXPERIMENTAL
Materials and Chemical Analysis
思量是什么意思The banana pudo-stems were harvested from a banana plantation in Gaozhou (Guangdong, China). The banana pudo-stem, which was parated from banana bunch and foliage, was about 30cm in diameter and 70cm in height. The layered outer bark can be parated from the pudo-stem into veral blocks by hand. Some samples deprived of pith were air-dried and ground, and the fractions that pasd a 40 mesh screen were collected and prerved for chemical analysis. The samples were first submitted to soxhlet extraction with ethanol/toluene (1:2, v/v) for 8h. The ash content, extractives, Klason lignin, holocellulo, cellulo, and pectin were determined following the TAPPI methods (T 211 om-93, T 204 cm-97, T 13, T 9, T 17). The cellulo content was determined by treating extractives-free samples with alcoholic nitric acid (4:1, v/v) solutions under reflux during four cycles of 1h. At the end, to calculate the final content of cellulo, one must subtract the ash content, becau the banana pudo-stem is rich in ash. The cellulo content was determined following the Kurschner-Hoffner approach, which consists of treating 1g of extractives-free samples with 25ml of alcoholic nitric acid solutions under reflux during four cycles of 1h. After each cycle, the solution was removed for a fresh volume. The alcoholic nitric acid solution involved mixing one volu
me of 65% (w/w) solution of nitric acid with four volumes of 96% purity ethanol. Hollocellulo was determined following the method of sodium chlorite, which consisted of 2g of extractives-free fractions with the mixture of 65ml distilled water, 0.5ml acetic acid, and 0.6g pure sodium chlorite during 1h at 75˚C. This treatment was repeated three times until the samples became white. The final content of holocellulo was calculated by subtracting the ash content due to the high ash content in the pudo-stem.
The polysaccharides of the banana pudo-stem materials were also analyzed. The holocellulo of banana pudo-stem was mixed with 72% H2SO4 in 30˚C for 2h, and then subjected to a hydrolytic process with 4% H2SO4 in 120˚C for 1h. Lastly, the monosaccharide in the hydrolyzate was determined by Ion Chromatography (IC) (Dionex, USA).
Obrvation with LM
楞读音The samples of banana pudo-stem were heated in boiling water to drive the internal air out, and then immerd in a mixture of 30% H2O2 and acetic acid at the ratio of 1:1(v/v). This process was carried out at 60˚C for 48h until the fibers became white and disperd, and the fibers were carefully prerved for LM and CLSM obrvation. In the end, some fibers were removed from the suspensio
n and placed with a dropper onto the glass slide, and then covered by a piece of coverglass and stained with Herzberg dye. At last, the sample of fibers from banana pudo-stem was analyzed under the Olympus bx51 light microscopy (Olympus, Japan).
Obrvation with CLSM
Before they were fixed on the glass slide, the banana pudo-stem fibers were preliminarily stained with acridine orange (AO). It was found that lignin contains a
美女头像微信detectable level of fluorochromic activity that can be detected by lecting suitable incident and obrved wavelength. It was reported (Li and Reeve 2004) that when the concentration of AO is sufficiently low, only lignin will be labeled and the fluorescence intensity of stained fibers can be correlated to the lignin distribution of fibers. Some wood materials have been studied with CLSM (Xu et al. 2006), but the lignin distribution in non-wood materials have never been reported. In this experiment, the banana pudo-stem fibers were immerd in the solution consisting of 1mg AO powder and 10ml deionized water for 1h at room temperature. After fluorescent staining, the residual dye was washed out with deionized water, and the washing was conducted three times. Finally, the fluorescently labeled fibers were mounted on glass slide and obrved under CLSM immediately to avoid fluorescence quenching.
Images were obtained using a Leica TCS SP5 CLSM device (Leica, Germany). An argon ion lar (488nm) was ud as the illumination light.
Obrvation with SEM
Different morphological parts of banana pudo-stem were removed and freeze-dried for SEM analysis. The samples of different parts were carefully cut to expo the inner wall and ektexine, and then the specimens were coated with a thin gold-palladium film. The obrvation was carried out under an LEO 1530VP SEM (Oxford, United Kingdom).
RESULTS AND DISCUSSION
Main chemical compositions, such as cellulo, holocellulo, lignin, extractives, and ash content of banana pudo-stem were determined in the chemical analysis. In addition, the holocellulo compositions were also determined with IC.
Chemical Composition
The moisture content of the fresh banana pudo-stem was about 96%. The amounts of chemical compositions in the raw material are listed in Table 1. In comparison with the traditional raw material
女人带貔貅的正确方法s ud in the pulp and papermaking industry, it was found that the content of holocellulo in banana pudo-stem was much lower than wood fibers (Gong 2007; Cai and Tao 2007), but still higher than straw, which is a typical kind of nonwood fiber (Liu et al 2003). However, banana pudo-stem had lower lignin content than wood and straw. While the ash and extractive contents in banana pudo-stem were higher than that of wood fibers, they were still lower than straw. In conclusion, the banana pudo-stem has potential in application of pulping and papermaking becau of its acceptable content of cellulo and holocellulo and low lignin content.
The holocellulo composition of banana pudo-stem is shown in Table 2. Gluco was the predominant monomer in this raw material with a 71.76% content, followed by xylo, 11.20%; arabino, 7.34%; galacto, 2.02%; manno, 0.58%; and galacturonic acid, 7.09%. Altogether, 97.90% of the holocellulo was compod by the monosaccharides.
Table 1. Chemical Composition* of Banana Stem and Some Other Raw
Materials工作述职报告范文
Table 2. Monosaccharides Composition of Banana Pudo-Stem and
holocellulo (qualitative proportion, %)
Sample Glu Xyl Gal Ara Man Glucuronic
acid
Galacturonic acid Pudo-stem 71.76 11.20 2.02 7.34 0.58 n.d.
7.09 Holocellulo 67.90 12.58 2.25 5.44 1.02
1.27 5.44
LM Analysis
Figures 1 and 2 are LM micrographs of banana pudo-stem. From Fig. 1 it is
obvious that plenty of parenchyma cells were contained in the banana pudo-stem, which caud high ash content and negative effects on the pulping and papermaking process. It can be discovered from Fig. 2 that the pudo-stem fiber is narrow and has a gmented structure (B in Fig. 2). The fiber has a regular shape, and the end (A in Fig. 2) is sharp, which agrees with the typical features of bast fibers (Wang 1999).
Obrvations with SEM and CLSM
It was reported by Ganan (2004) that the fiber bundles of banana pudo-stem are
covered with a layer of membrane compod of hemicellulo and pectin. After removal of the non-cellulo components, the fiber bundles prent a complex hierarchically microordered structure formed by microsized fibers with two orientations. The fibers constructing this structure can be divided into elementary fibers and narrow fibers according to their orientation. The elementary fibers, in the diameter range of 10 to 15μm, are oriented in the bundle direction, while the narrow fibers in the diameter range of 3 to 4μm are intertwined around the elementary fibers.
(%) Cellulo Holocellulo Klason
lignin Acid-soluble lignin
Ash content Extracts Pectin Banana stem
39.12 72.71 8.88 1.90 8.20 3.05 0.27 Aspen (Gong,2007)
45 77.64-79.22 22.37-23.40 2.05-2.38 0.52-1.03 2.00-2.20 - Straw
(Liu et al. 2003)
36.20 63.1 11.30 4.15 12.87 7.45 - Pine (Cai and Tao 2007)
45 71-83 24.57-29.85 0.37 0.27-0.28 1.11-3.51 - * The composite contents are bad on dried raw materials
