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Synergistic enzymatic hydrolysis of cassava starch and anearobic digestion of cassava waste.

机译：木薯淀粉的协同酶水解和木薯废物的厌氧消化。

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摘要

Cassava is a major root crop and source of food and feed carbohydrate for humans and livestock. Cassava provides economic and subsistence value to more than 800 million to one billion people in Brazil, China, Haiti, India, Indonesia, Nigeria, Thailand and many other countries. However, current processes for conversion of cassava roots to value added products are far from optimum. Glucose is produced by first extracting starch from the roots. The starch is then subjected to two separate operations called liquefaction and saccharification. Each operation incurs many cost elements. Liquefaction for example demands elaborate equipment and energy inputs, while starch extraction is energy, labor and technology intensive. These requirements place glucose and other value added cassava products beyond the reach of many developing nations. It would be efficient and advantageous if liquefaction and saccharification could be carried out simultaneously as one operation and the starch hydrolyzed directly without going through the extraction procedure. Furthermore, over 60 % of global cassava output (which was 252.2 x 109 kg in 2011) is processed annually for human food, generating enormous quantities of organic waste matter with attendant environmental and disposal issues. Anaerobic digestion of cassava wastes could generate beneficial products and at the same time be environment friendly.;The objectives of this study were to develop and demonstrate a village-scale method of processing fresh cassava root into flour from solar-convection dried cassava chips, produce glucose sweetener from combined liquefaction and saccharification hydrolysis of native starch that was not first extracted, and generate biogas (methane) from anaerobic digestion of cassava waste.;A solar convection dryer requiring no fuel or electricity was used to dry thin slices of cassava root into dry chips that were subsequently ground into cassava flour. The flour as well as freshly ground cassava root (pulp) was used as substrate for conversion into glucose by enzyme hydrolysis. The rates of conversion (kinetics) for both substrates were determined at two different temperatures and compared with those of commercially available refined cassava starch. Cassava waste from peelings and trimmings was used as feedstock for anaerobic digestion into methane fuel.;Results showed that rates of reaction for hydrolysis of all three substrates were similar to each other at both temperatures, but resulted in different extent of reaction. The cassava flour and pulp produced syrup with 3-4% glucose, while the commercial starch produced 10% glucose within 4 hours at 60°C, and 72 hours at 37°C. Anaerobic digestion of cassava waste produced bio-methane yield of 0.25 liter/ gram volatile solids with a production efficiency of 71 %. These findings would suggest the possibility of a cottage industry cassava processing operation that would be self-sufficient in which fresh cassava roots could be solar-convection dried to make flour. The flour and grated root pulp could be hydrolyzed in one step to make glucose syrup sweetener, while the waste peelings and trimmings could be processed by anaerobic digestion to produce useful energy in the form of biogas for maintaining digester temperature and/or supplementing heat required for hydrolysis and in the solar dryer. In addition, amylolytic (starch hydrolyzing) enzymes could be harvested from the anaerobic digestion liquor, and the post digestion effluent applied to farm land as source of organic fertilizer.
机译：木薯是主要的根系作物，是人类和牲畜食物和饲料碳水化合物的来源。木薯为巴西，中国，海地，印度，印度尼西亚，尼日利亚，泰国和许多其他国家的8亿至10亿人口提供经济和生存价值。但是，当前将木薯根转化为增值产品的过程远非最佳。通过首先从根中提取淀粉来生产葡萄糖。然后将淀粉进行两个独立的操作，即液化和糖化。每个操作都会产生许多成本要素。例如，液化需要复杂的设备和能量输入，而淀粉提取需要大量的能源，劳动力和技术。这些要求使葡萄糖和其他增值的木薯产品超出了许多发展中国家的承受范围。如果液化和糖化可以作为一种操作同时进行并且淀粉直接水解而不经过提取程序，那将是有效和有利的。此外，全球每年有超过60％的木薯产量（2011年为252.2 x 109千克）用于人类食品加工，产生了大量的有机废物，并伴随着环境和处置问题。木薯废物的厌氧消化可以产生有益的产品，同时也有利于环境。这项研究的目的是开发和证明一种乡村规模的方法，该方法是将对流干燥的木薯片加工成新鲜的木薯根，制成面粉，生产葡萄糖的甜味剂是由未先提取的天然淀粉液化和糖化水解联合得到的，但未经过木薯废物的厌氧消化而产生沼气（甲烷）。使用太阳能对流干燥机，无需燃料或电力，将木薯根切成薄片干薯片，然后将其磨成木薯粉。面粉以及新近磨碎的木薯根（纸浆）用作通过酶水解转化为葡萄糖的底物。在两种不同的温度下测定两种底物的转化率（动力学），并将其与市售精制木薯淀粉进行比较。木屑和去皮屑产生的木薯废物被用作厌氧消化成甲烷燃料的原料。结果表明，在这两个温度下，所有三种底物的水解反应速率彼此相似，但导致反应程度不同。木薯粉和纸浆产生的糖浆含3-4％的葡萄糖，而商品淀粉在60°C的4小时内和37°C的72小时内产生10％葡萄糖。木薯废物的厌氧消化产生的生物甲烷产量为0.25升/克挥发性固体，生产效​​率为71％。这些发现将表明家庭手工业木薯加工操作的可能性是自给自足的，其中可以将新鲜的木薯根进行对流干燥以制成面粉。面粉和磨碎的根浆可以一步水解成葡萄糖浆甜味剂，而废物的果皮和切屑可以通过厌氧消化处理，以沼气的形式产生有用的能量，以维持消化温度和/或补充热量。水解和在太阳能干燥器中。此外，可以从厌氧消化液中收获淀粉分解酶（淀粉水解酶），并将消化后的废水作为有机肥料来源应用于农田。

著录项

  • 作者

    Aso, Samuel Nwanele.;

  • 作者单位

    University of Florida.;

  • 授予单位 University of Florida.;
  • 学科 Engineering Agricultural.;Agriculture Food Science and Technology.;Chemistry Biochemistry.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 324 p.
  • 总页数 324
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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