**2. Materials and methods**

#### **2.1. Material**

such as H2SO4, HCl, HNO3, CH3COOH, HCOOH, H3PO4, and NaOH, KOH, CaOH2, NH3 H2O in the ball milling pretreatment of corn stover [6]. Bjerre et al. studied the wet oxidation process of wheat straw as a pretreatment method. By using a specially constructed auto‐ clave system, the wet oxidation process was optimized with respect to both reaction time and temperature (20 g/L straw, 170℃, 5 to 10 min) and gave about 85% w/w yield of con‐ verting cellulose to glucose [7]. Zhu and Pan evaluated the performances of three of the most promising pretreatment technologies, including steam explosion, organosolv, and sul‐ fite pretreatment to overcome lignocelluloses recalcitrance (SPORL) for softwood pretreat‐ ment. SPORL was the most efficient process and produced highest sugar yield [8]. Keshwani et al. examined the feasibility of microwave pretreatment to enhance enzymatic hydrolysis of switchgrass. It was found that the application of microwave radiation for 10 minutes at 250 watts to switchgrass immersed in 3% sodium hydroxide solution (w/v) produced the highest yields of reducing sugar [9]. Yu et al. studied a two-step liquid hot water pretreat‐ ment (TSLHW) mehod. The first step of pretreatment was temperature range from 180 to 200℃, and the highest yield of total xylose achieved was 86.4% after 20 min at 180℃. The second-step of pretreatment was temperature range from 180 to 240℃ for 0-60 min. The op‐ timum reaction conditions of pretreatment with minimal degradation of sugars were 200℃ for 20 min [10]. Sulfuric acid is widely used for acid pretreatment among various types of acid such as hydrochloric acid, nitric acid and phosphoric acid [11]. Maarten et al. compared the efficiencies of fumaric, maleic, and sulfuric acid in wheat straw pretreatment. At 150℃ and 20-30% (w/w) dry wheat straw, the pretreatment with dilute fumaric or maleic acid could be a serious alternative to dilute sulfuric acid pretreatment [12]. Sun et al. studied the effectiveness of different alkaline solutions by analyzing the delignification and dissolution of hemicelluloses in wheat straw. The optimal process condition was 1.5% NaOH for 144h at

4 Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization

20℃, releasing 60% and 80% lignin and hemicelluloses, respectively [13].

**Figure 1.** Simplified impact of pretreatment on biomass modified from Mosier et al. [5]

Moso bamboo aging with 4 years was used in this study. They were taken from a bamboo plantation located in Anhui province, China. The initial moisture content of samples was about 6.13%, and the density was about 0.65g/cm3. Bamboo materials were cut off to sample size 40mm (longitudinal) by 3-8mm (radial) by 20-30mm (tangential). Then, they were broken down to particles with a Wiley mill and the size of bamboo particles used in the test was about 250-425 um. Finally, the particles were dried at 105℃ until mass variability of samples was less than 0.2%.

**3. Results and discussion**

The functional groups of untreated and pretreated bamboo were shown in the FTIR spectra presented in Figure 2. For untreated bamboo, there was a strong broad O-H stretching absorbance at 3350cm-1. The absorbance at 2910 cm-1 was a prominent C-H stretching. In the fingerprint region (from 1800 to 800 cm-1), some important information on various functional groups presented in untreated bamboo. The absorbance at 1740 cm-1 was attributed to C=O stretching vibration in hemicelluloses. The bands from 1600 to 1450 cm-1 was due to aromatic skeletal vibration in lignin. The absorbance at 1370cm-1 was C-H bending of cellulose or hemicelluloses, and that of 1230cm-1 was C-O stretching of phenolic hydroxyl group in the lignin. The absorbance at 1160cm-1 and 1030 cm-1 was respectively attributed to C-O-C stretching of cellulose or hemicelluloses and C-O stretching of cellulose, hemicelluloses or

Characteristics of Moso Bamboo with Chemical Pretreatment

http://dx.doi.org/10.5772/55379

7

The chemical group difference of bamboo-H2SO4 and bamboo was showed in Figure 3. It was very obvious that the number of most chemical groups on the bamboo-H2SO4 sample surface was more than that of untreated bamboo surface, except for absorption of C=O stretching vibration. The information is very important, which confirms the removal of hemicelluloses of bamboo. The main feature of difference between hemicelluloses and cellulose is that hemicelluloses has branches with short lateral chains consisting of different sugars. These monosaccharides include pentoses (xylose, rhamnose, and arabinose), hexoses (glucose, mannose, and galactose), and uronic acids (e.g., 4-omethylglucuronic, D-glucuronic, and Dgalactouronic acids) [29]. Hemicelluloses is known to coat the cellulose microfibrils in the plant cell wall, forming a physical barrier to access by hydrolytic enzymes. Removal of hemicellu‐ loses from the microfibrils is believed to expose the cellulose surface and to increase the enzymatic hydrolysis of cellulose [17, 18]. Dilute-acid pretreatment is a main method for the selective fractionation of hemicelluloses from biomass. Both cellulose and hemicelluloses components can also be hydrolysed using dilute-acid catalysed processes but in this case a two step-hydrolysis is required. The difference between two steps is mainly the operational

temperature, which is high in the second step (generally around 230-240 ℃) [19, 20].

The chemical group difference of bamboo-NaOH and bamboo was showed in Figure 4. It was found that the number of all chemical groups on the bamboo-NaOH sample surface was less than that of bamboo surface. This indicated the removal of hemicelluloses and lignin of bamboo. Alkaline pre-treatments are very effective for lignin solubilisation exhibiting only minor cellulose and slightly higher hemicelluloses solubilisation [21]. Generally, alkaline pretreatments include wet oxidation and the ammonia. The wet oxidation was used in this research. Wet oxidation is defined as pretreatment process including oxygen and water at elevated temperatures and pressure, promoting the oxidation of lignin and decomposing it to CO2, H2O and carboxylic acids [22, 23]. The hemicellulosic sugars remain mainly in the oligomeric form, and although there is a low formation of furan-aldehydes, a significant formation of carboxylic acids still exists [24]. It is well known that lignin confers integrity and structural rigidity on the plant cell wall. There is several information that cellulolytic enzymes

**3.1. FTIR analysis**

lignin [16].

#### **2.2. Pretreatment**

Bamboo particles were pretreated using a microwave accelerated reaction system. 2% of sulfuric acid (w/w of H2SO4/bamboo) and 10% sodium hydrate (w/w of NaOH/bamboo) were used in the pretreated process. About 3g bamboo particles were mixed with the solvent in a 100 mL vessel. The mass ratio of liquor-to-bamboo was about 8:1. The vessel with samples was positioned at the centre of a rotating circular ceramic plate in the microwave oven for pre‐ treatment at the power level of 400 W. The temperature was raised to 180 ℃ (target tempera‐ ture) in about 10 min and maintained for an additional 30min. After the pretreatment, a few minutes were allowed for the temperature to drop down below 50 ℃, and then pretreated substrate and spent liquor were then separated by filtration. The substrate was washed using distilled water until pH value of washed liquor was about 7. Each experiment was carried out in three times and average results were reported.

#### **2.3. Property test**

#### **1.** FTIR test

The functional group difference of untreated and pretreated samples was analyzed by means of FTIR-spectrometer (Bruker, Bremen, Germany). The concentration of the sample in the tablets was constant of 1 mg/400 mg KBr. Scans were run at a resolution of 4cm-1 and each sample consisted of 64 scans recorded in absorbance units from 3800 to 750cm-1. The spectra were ATR and baseline corrected and the spectra analyzed for carbonyl bands using relative indices. A minimum of two samples were tested, and data from the first run was used when it was shown to be in accordance with the second run. The experimental data could be directly obtained though FTIR-spectrometer, but they were analyzed by using Origin 8.0 software.

#### **2.** XRD test

XRD test of untreated and pretreated bamboo samples was carried out using an X-ray diffractometer (Diffraktometer D5000, Siemens, Germany) with an X-ray generator and a Co target (λ=0.1729 nm) at a scanning speed of 3º/min, and the data were recorded every 0.02º (2θ) for the angle range of 2θ=5-45º. The cellulose crystallinity (CrI) was calculated based on formula (1):

$$\text{CrI} = \left(\text{I}\_{002}\text{-I}\_{\text{am}}\right) / 1002 \tag{1}$$

Where, I002 was the overall intensity of the peak at 2θ about 22º and Iam was the intensity of the baseline at 2θ about 18º.
