香蕉茎秆酶法脱胶工艺及其脱胶纤维性能

为了将生物质废弃物香蕉茎秆进行高值化利用,采用酶法脱胶工艺制备香蕉茎秆纤维。研究超声预处理工艺中频率、处理温度对香蕉茎秆脱胶率的影响,确定较佳的超声预处理工艺。将预处理后的香蕉茎秆粗纤维进行半纤维素酶、果胶酶脱胶,分别考察缓冲液pH、酶浓度、反应温度对脱胶率的影响。结果表明:预处理工艺中超声处理的较佳频率为40 kHz,温度为70℃;酶法脱胶工艺中较佳的半纤维素酶缓冲液pH为5.5,半纤维素酶浓度为0.004 g·ml^-1,反应温度为50℃;较佳的果胶酶缓冲液pH为6.0,果胶酶浓度为0.003 g·ml^-1,反应温度为55℃。采用傅里叶红外光谱(FTIR)、X射线衍射(XRD)和扫描电镜(SEM)分析酶法较佳工艺制备的香蕉茎秆纤维的理化特性;并对其机械性能进行测试与分析。FTIR及XRD结果表明:酶法较佳工艺制备的香蕉茎秆纤维去除了半纤维素和大部分果胶,相对结晶度为66.4%;机械性能测试结果表明酶法较佳工艺制备的香蕉茎秆纤维的拉伸强度、杨氏模量和断裂伸长率分别是118.48 MPa,15.15 GPa,0.67%。

Enzyme degumming process of banana pseudostem fibers and characterization of degummed fibers

In order to utilize the banana pseudostems, a rich biomass resource in Hainan, the fibers were extracted from banana pseudostem by enzyme treatment. In this work, the better process conditions of frequency and temperature in ultrasonic pretreatment were determined, and two enzymes, hemicellulase and pectinase, were used to remove pectin and hemicelluloses, and to loose the compact structure of fibers, respectively. The better degummed process conditions of the concentration of these two enzymes, reaction temperature and pH value in enzyme process were optimized in terms of degummed rate. The optimum parameters were determined as: the concentration of hemicellulase 0.004 g·ml^-1, reaction temperature 50℃, pH value 5.5, concentration of pectinase 0.003 g·ml^-1, reaction temperature 55℃ and pH value 6.0. Chemical characterization of the banana pseudostem fibers confirmed that the cellulose content was increased from 60% to 65% due to the application of enzyme treatments. The physicochemical properties of enzyme treated banana pseudostem fibers were analyzed by using the fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The tensile properties of enzyme treated banana pseudostem fibers were also investigated. The FTIR and XRD analyses of the enzyme treated banana pseudostem fibers showed an obvious reduction in amount of noncellulosic substances with a crystallinity index of 66.4%. Surface morphological studies using SEM revealed that the enzyme treated banana pseudostem fibers had a rougher surface with a lot of little pectin substance and exhibited brittle fracture. The tensile tests revealed that the tensile strength was about 118.48 MPa with Young's modulus of 15.15 GPa and elongation at break of 0.67%.