摘要
Demand for petroleum-derived products has been growing over the years. To reduce fossil fuel dependence, renewable materials have been explored for alternative transportation fuels. In the US, the use of corn for biofuel production has implication on other markets that utilize corn for animal feed and competes with land needed for food production. Sweetpotato ( Ipomoea batatas ) is an important starch-based crop grown worldwide with agronomic benefits including low requirements of fertilizer and drought tolerance. Sweetpotatoes bred for high starch content (>70 % in dry matter basis), referred to as industrial sweetpotatoes (ISPs), have the additional benefit of growth on marginal lands. The high starch content and yield per unit of land cultivated makes ISPs attractive alternative starch feedstocks for industrial applications. Conversion of sweetpotato to sugars has been achieved using thermotolerant enzymes during liquefaction and saccharification of the starch. Resulting sugars can be used to produce ethanol and/or other sugar-based value-added chemicals. The overall goal of this project was to evaluate the potential use of North Carolina ISPs (lines NC-413 and DM02-180) as an alternative starch feedstock for value-added products production and to further examine their needed conversion parameters. The specific objectives of the project were to: 1) evaluate starch hydrolysis and glucose production rates in the ISPs lines as fresh and flour preparations and compare them with Covington, an important the table-stock sweetpotato; 2) determine process conditions and assess ethanol production potential through Separate Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) of flour ISPs preparations using the yeasts Kluyveromyces marxianus NCYC 851 and Ethanol Red (Saccharomyces cerevisiae ). Additionally, for the purple-fleshed NC-413 ISP line, examine anthocyanin yield through Simultaneous Extraction and Fermentation (SEF) methods; and 3) determine the potential of Near Infrared Spectroscopy (NIRS) and develop models for prediction of major sweetpotato constituents (moisture, protein, fiber, and starch) during processing to provide a rapid analytical tool to replace standard lab methods. Results from the saccharification studies showed that differences in chemical composition among the sweetpotato cultivars affected the starch digestibility and that ISPs had greater starch conversion and glucose production (>0.5 g/g dry ISP) than the table-stock Covington. Considering the most promising hydrolysis conditions found, the yeast K. marxianus was investigated for its ethanol production potential at higher temperatures and compared with S. cerevisiae in SHF and SSF. Fermentation by S. cerevisiae during SHF had a maximum ethanol yield of 0.32 g/g dry ISP, a 1.1-fold increase above that produced by K. marxianus. Subsequent studies showed that ethanol yield increased in a SSF system and that higher yeast concentrations significantly enhanced ethanol production. Maximum ethanol production at 0.39 g/g dry ISP was obtained in a SSF system using S. cerevisiae, 15% greater than that produced by K. marxianus under the same conditions. A SEF of flour purple-fleshed ISP was conducted in order to evaluate the effect of pH on recovery of anthocyanins and ethanol production. Total monomeric anthocyanin (TMA) concentration was measured and it was found that non adjusted pH produced more ethanol than the fermentations with an adjusted pH of 4.5. It was possible to extract 64.4 mg cyanidin-3-glu/100 g dry powder (22.1 mg cyanidin-3-glu/100 g fresh weight) and produce 0.34 g ethanol /g dry ISP demonstrating that SEF can be used to reduce chemical and energy inputs for anthocyanin extraction. The combination of high dry matter and anthocyanin content in the purple-fleshed ISP line make it a suitable substrate for production of industrial colorants and ethanol. This work also developed calibration models to predict the major constituents of biologically processed sweetpotatoes using NIRS. Our calibrated and validated models indicated that NIRS is a tool capable of rapidly predicting the composition of different constituents present in sweetpotato samples before and after exposure to conversion process conditions.
摘要译文
对于石油衍生产品的需求一直在增长多年。为了减少对化石燃料的依赖，可再生材料已经探讨了替代运输燃料。在美国，利用玉米用于生物燃料生产对，利用玉米用于动物饲料等市场含义和竞争所需要的粮食生产用地。甘薯（甘薯）与农艺的好处，包括化肥和耐旱性要求低的全球增长的一个重要的淀粉为基础的作物。Sweetpotatoes饲养淀粉含量高（\u003e 70％25在干物质的基础上），被称为工业sweetpotatoes商（ISP），具有增长对边际土地的额外好处。高淀粉含量和单产的土地耕种，使互联网服务供应商有吸引力的替代淀粉为原料的工业应用。甘薯转化为糖已使用液化淀粉的糖化过程中耐热酶已经实现。所得的糖可用于生产乙醇和/或其他基于糖的附加值的化学品。该项目的总体目标是评估潜在用途北卡罗莱纳州互联网服务供应商（线NC-413和DM02-180）作为替代淀粉原料附加值产品的生产，并进一步审视自己的需要转换参数。该项目的具体目标是：1）评估水解淀粉和葡萄糖生产速率的互联网服务供应商线新鲜和面粉制品，并与科文顿，一个重要的表，股票甘薯比较;2）确定的工艺条件，并通过使用该酵母马克斯克鲁NCYC 851和乙醇红色（酿酒酵母）面粉的ISP制剂单独水解和发酵（SHF），并同时糖化和发酵（SSF）的评估乙醇生产潜力。此外，为紫肉NC-413的ISP线路，通过检查同时提取和发酵（SEF）方法花青素产量;3）确定近红外光谱（NIRS）的潜力，并在加工过程中提供快速的分析工具，以替代标准的实验室方法开发模式主要成分甘薯（水分，蛋白质，纤维和淀粉）的预测。结果从糖化研究表明，甘薯品种间在化学成分的差异影响了淀粉消化率和互联网服务供应商具有更大的淀粉转化和葡萄糖产量（\u003e为0.5g / g干ISP）的比表库存科文顿。考虑发现最有希望的水解条件下，酵母马克斯克鲁维进行了研究其乙醇生产潜力在较高的温度，并与酿酒酵母在SHF和SSF比较。SHF在发酵过程中由酵母有0.32克/克干ISP，1.1倍以上，通过马克斯克鲁维生产的最大乙醇产量。随后的研究表明，乙醇产量增加一个SSF系统和更高的酵母浓度显著增加的乙醇生产。使用酿酒酵母的SSF系统获得最大乙醇产量0.39克/克干的ISP，15％25比由马克斯克鲁维在相同条件下产生的更大。面粉紫肉的ISP的SEF是为了评价pH对花色素苷和乙醇生产的恢复的影响下进行。总单体花青素（TMA）浓度进行测定，其结果发现，非调pH产生比为4.5的PH值调节到的发酵更多的乙醇。这是可能的提取64.4毫克矢车菊-3-谷氨酸/ 100克干粉末（22.1毫克矢车菊-3-谷氨酸/ 100克鲜重），并产生0.34克乙醇/ g干的ISP证明，认为SEF可用于减少化学和能源投入的花青素萃取。高干物质和紫肉ISP线路花青素含量相结合，使其成为一个合适的衬底生产工业着色剂和乙醇。这项工作还开发了校准模型来预测用近红外生物处理sweetpotatoes的主要成分。我们的校准和验证模型表明，近红外光谱是能够快速预测本甘薯样品之前在和曝光到转换处理条件之后的不同成分的组合物的工具。
Diaz Isaya, Joscelin Teresita. Bioprocessing of Industrial Sweetpotatoes for Biobased Products[D]. US: North Carolina State University, 2013