酶预处理对马尾松纤维细胞壁结构及微纤丝制备的影响研究
发布时间：2018-11-23 18:23
【摘要】：纤维素微纤丝(CMF)由于其强度高、重量轻、可再生的特点,以及其表现出的良好的生物相容性、可降解性和阻隔性能而备受关注。由于机械解离制备CMF所需能耗过高,并且产品尺寸分布不均匀,因此CMF很难实现产业化。生物酶预处理是解决该问题的一个有效方法,先对纤维原料进行预处理,降低微纤丝之间的结合力,使其易于微纤化,然后再进行机械解离,可以大幅降低机械能耗。本课题重点研究酶预处理对细胞壁结构的影响以及酶预处理对机械解离制备CMF的促进作用。通过控制漂白马尾松纤维的酶预处理程度的方式来改变纤维细胞壁的结构,然后进行不同程度的高压均质处理,以此来探究纤维细胞壁结构对于机械解离的影响,从而揭示酶预处理促进机械解离制备CMF的机理。在酶水解过程中,纤维细胞壁发生切断、撕裂、剥皮、润胀和侵蚀。漂白马尾松纤维表面存在大量纹孔呈线性排列,撕裂作用主要发生在纹孔所在区域。断头率和扭结纤维含量的变化反映了纤维被切断的程度。漂白马尾松纤维经5.0FPU/g纤维素酶降解2h后,纤维被切断次数达到最大,约为3~4次。随酶用量的增加,细胞壁比表面积呈现先减小后增加再减小再增加的“W型”变化,纤维素结晶度的变化趋势恰好与之相反,呈现先增加后减小再增加再减小的“M型”变化;纤维素酶经细胞壁的中孔和大孔进入细胞壁结构内部,随着酶用量的增加,中孔总体积先增加然后保持稳定,大孔总体积先增加后减少,微孔总体积稍有减小,总孔体积的变化趋势与大孔总体积的变化趋势相同。微纤化主要局限于细胞壁的表面,沿细胞壁本身向边缘蔓延,最终细胞壁被完全解离,进而得到CMF。酶预处理破坏纤维细胞壁结构,提高比表面积,使得微纤化区域增加,促进细胞壁的解离。高压均质处理程度越高,纤维的微纤化程度越高,相应的机械能耗也越高。随着均质次数的增加,纤维粒径、纤维素平均聚合度呈下降趋势,纤维保水值和热稳定性以及CMF薄膜透光率呈上升趋势。高压均质机的能耗主要取决于物料体积和均质次数,固含量对其影响较小。纤维素酶预处理破坏了纤维细胞壁的基本结构,形成具有较大比表面积的纤维碎片和片段,增加了微纤化发生的区域。分别以CMF直径分布、能量消耗、纤维素平均聚合度和CMF薄膜透光率为指标,评价酶预处理对机械解离制备CMF的促进作用。结果表明,漂白马尾松纤维在100MPa压力下均质处理30次后得到的MFC的聚合度为354,直径主要分布在20~50nm;漂白马尾松纤维在50℃下经10.0FPU/g纤维素酶水解2h,在100MPa压力下均质处理30次后得到的MFC的聚合度为229,直径主要分布在10~40nm。相同均质条件下,解离酶预处理纤维较解离原料纤维而言,能量消耗更少,且解离效果更好。
[Abstract]:Cellulose microfibrillar (CMF) has attracted much attention due to its high strength, light weight, reproducibility, and its good biocompatibility, degradability and barrier properties. Because the energy consumption of mechanical dissociation to prepare CMF is too high and the product size distribution is not uniform, it is difficult to realize the industrialization of CMF. Biological enzyme pretreatment is an effective method to solve this problem. Firstly, pretreatment of fiber raw materials to reduce the adhesion between microfibrils, make it easy to micro-fibrillate, then mechanical dissociation, can greatly reduce the mechanical energy consumption. The effect of enzyme pretreatment on cell wall structure and the effect of enzyme pretreatment on the preparation of CMF by mechanical dissociation were studied. By controlling the degree of enzyme pretreatment of bleached Masson pine fiber, the structure of cell wall was changed, and then treated with different degrees of high pressure homogenization, so as to explore the effect of cell wall structure on mechanical dissociation. Therefore, the mechanism of enzyme pretreatment promoting mechanical dissociation to prepare CMF was revealed. During enzymatic hydrolysis, the cell wall is cut, torn, peeled, swelled and eroded. A large number of holes on the surface of bleached Masson pine fiber were linearly arranged, and the tearing action mainly occurred in the region where the holes were located. The change of breakage rate and kink fiber content reflects the degree of fiber being cut off. When the bleached Masson pine fiber was degraded by 5.0FPU/g cellulase for 2 hours, the number of cut off reached the maximum, about 34 times. With the increase of enzyme dosage, the specific surface area of cell wall showed a change of "W type" which decreased first, then increased then decreased, and then increased. The change trend of cellulose crystallinity was just the opposite, showing the change of "M type" which increased first and then decreased. Cellulase entered the cell wall structure through the mesopore and macropore of the cell wall. With the increase of the amount of enzyme, the total volume of the mesopore first increased and then remained stable, the total volume of the macropore increased first and then decreased, and the total volume of the micropore decreased slightly. The change trend of total pore volume is the same as that of large pore volume. Microfibrillarization is mainly confined to the surface of the cell wall, spreading along the cell wall itself to the edge. Finally, the cell wall is completely dissociated and CMF. is obtained. Enzyme pretreatment destroyed the cell wall structure, increased the specific surface area, increased the microfibrillarization area, and promoted the dissociation of the cell wall. The higher the treatment degree of high pressure homogenization, the higher the degree of fiber microfibrillation and the higher the corresponding mechanical energy consumption. With the increase of homogenization times, the particle size and average polymerization degree of cellulose decreased, the water retention value and thermal stability of fiber and the transmittance of CMF film increased. The energy consumption of high pressure homogenizer mainly depends on the volume of material and the times of homogenization, and the content of solid has little effect on it. The cellulase pretreatment destroyed the basic structure of the cell wall, formed fiber fragments and fragments with large specific surface area, and increased the area of microfibrillation. Based on the diameter distribution of CMF, energy consumption, average polymerization degree of cellulose and transmittance of CMF film, the effect of enzyme pretreatment on the preparation of CMF by mechanical dissociation was evaluated. The results showed that the degree of polymerization of bleached Masson pine fiber after 30 times homogenization treatment under 100MPa pressure was 354, and the diameter of MFC was mainly distributed at 20 ~ 50nm. Bleached Masson pine fiber was hydrolyzed by 10.0FPU/g cellulase at 50 鈩，
本文编号：2352356
[Abstract]:Cellulose microfibrillar (CMF) has attracted much attention due to its high strength, light weight, reproducibility, and its good biocompatibility, degradability and barrier properties. Because the energy consumption of mechanical dissociation to prepare CMF is too high and the product size distribution is not uniform, it is difficult to realize the industrialization of CMF. Biological enzyme pretreatment is an effective method to solve this problem. Firstly, pretreatment of fiber raw materials to reduce the adhesion between microfibrils, make it easy to micro-fibrillate, then mechanical dissociation, can greatly reduce the mechanical energy consumption. The effect of enzyme pretreatment on cell wall structure and the effect of enzyme pretreatment on the preparation of CMF by mechanical dissociation were studied. By controlling the degree of enzyme pretreatment of bleached Masson pine fiber, the structure of cell wall was changed, and then treated with different degrees of high pressure homogenization, so as to explore the effect of cell wall structure on mechanical dissociation. Therefore, the mechanism of enzyme pretreatment promoting mechanical dissociation to prepare CMF was revealed. During enzymatic hydrolysis, the cell wall is cut, torn, peeled, swelled and eroded. A large number of holes on the surface of bleached Masson pine fiber were linearly arranged, and the tearing action mainly occurred in the region where the holes were located. The change of breakage rate and kink fiber content reflects the degree of fiber being cut off. When the bleached Masson pine fiber was degraded by 5.0FPU/g cellulase for 2 hours, the number of cut off reached the maximum, about 34 times. With the increase of enzyme dosage, the specific surface area of cell wall showed a change of "W type" which decreased first, then increased then decreased, and then increased. The change trend of cellulose crystallinity was just the opposite, showing the change of "M type" which increased first and then decreased. Cellulase entered the cell wall structure through the mesopore and macropore of the cell wall. With the increase of the amount of enzyme, the total volume of the mesopore first increased and then remained stable, the total volume of the macropore increased first and then decreased, and the total volume of the micropore decreased slightly. The change trend of total pore volume is the same as that of large pore volume. Microfibrillarization is mainly confined to the surface of the cell wall, spreading along the cell wall itself to the edge. Finally, the cell wall is completely dissociated and CMF. is obtained. Enzyme pretreatment destroyed the cell wall structure, increased the specific surface area, increased the microfibrillarization area, and promoted the dissociation of the cell wall. The higher the treatment degree of high pressure homogenization, the higher the degree of fiber microfibrillation and the higher the corresponding mechanical energy consumption. With the increase of homogenization times, the particle size and average polymerization degree of cellulose decreased, the water retention value and thermal stability of fiber and the transmittance of CMF film increased. The energy consumption of high pressure homogenizer mainly depends on the volume of material and the times of homogenization, and the content of solid has little effect on it. The cellulase pretreatment destroyed the basic structure of the cell wall, formed fiber fragments and fragments with large specific surface area, and increased the area of microfibrillation. Based on the diameter distribution of CMF, energy consumption, average polymerization degree of cellulose and transmittance of CMF film, the effect of enzyme pretreatment on the preparation of CMF by mechanical dissociation was evaluated. The results showed that the degree of polymerization of bleached Masson pine fiber after 30 times homogenization treatment under 100MPa pressure was 354, and the diameter of MFC was mainly distributed at 20 ~ 50nm. Bleached Masson pine fiber was hydrolyzed by 10.0FPU/g cellulase at 50 鈩，
本文编号：2352356
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