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首页> 外文学位 >Sequential saccharification and fermentation of corn stover for the production of fuel ethanol using wood-rot fungi, Saccharomyces cerevisiae and Escherichia coli K011.
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Sequential saccharification and fermentation of corn stover for the production of fuel ethanol using wood-rot fungi, Saccharomyces cerevisiae and Escherichia coli K011.

机译：玉米秸秆的顺序糖化和发酵，用于利用木腐真菌，酿酒酵母和大肠杆菌K011生产燃料乙醇。

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摘要

We aim to develop a sequential biological process that converts cellulosic materials into fermentable sugars and ultimately ethanol as a transportation fuel. We performed solid state fermentation at ambient conditions to induce lignocellulolytic activities from three fungal species, namely Phanerochaete chrysosporium, Gloeophyllum trabeum and Trichoderma reesei. We cultivated each of the fungal species on pure cellulose and corn stover to induce the secretion of cellulases, hemicellulase and lignolytic enzymes via solid state fermentation for several days. Corn stover was chosen as the main material as it is one of the most abundant agricultural residues. The mold mediated processes liberate simple carbohydrates, suitable substrates for downstream microbial utilization. Next, we performed simultaneous saccharification and fermentation (SSF) of the cellulosic materials to produce more sugars that are converted to ethanol.;Prior to the SSF studies on the corn stover, we initially performed enzymatic studies of these fungal species on pure cellulose to evaluate their in situ enzyme production and hydrolytic abilities. Filter paper was used in the screening in accordance to the recommendations of several previously reported studies. The efficiency of the fungal species in saccharifying the filter was compared against a low dose (25 FPU/g cellulose) of a commercial cellulase. Results indicated that the most efficient fungal species in saccharifying the filter paper was T. reesei with 5.13 g/100 g filter paper of ethanol being produced at days 5, followed by P. chrysosporium at 1.79 g/100 g filter paper. No ethanol was produced from the filter paper treated with G. trabeum throughout the five day fermentation stage. Acetic acid was only produced in the sample treated with T. reesei and the commercial enzyme, with concentration 0.95 g and 2.57 g/100 g filter paper, respectively at day 5.;Next, we performed enzymatic saccharification of corn stover using P. chrysosporium and G. trabeum. Subsequent fermentation of the saccharification products to ethanol was achieved via the use of Saccharomyces cerevisiae and Escherichia coli K011. During the SSF period with S. cerevisiae or E. coli , ethanol production was highest on day 4 for all samples inoculated with either P. chrysosporium or G. trabeum. For the corn stover treated with P. chrysosporium, the conversion of corn stover to ethanol was 2.29 g/100 g corn stover for the sample inoculated with S. cerevisiae, whereas for the sample inoculated with E. coli K011, the ethanol concentration was 4.14 g/100 g corn stover. While for the corn stover treated with G. trabeum, the conversion of corn stover to ethanol was 1.90 g and 4.79 g/100 g corn stover for the sample inoculated with S. cerevisiae and E. coli K011, respectively.;In the later stages of our study, we further explore the coupling of mild chemical (dilute NaOH) and biological pretreatment and saccharification on the corn stover. Ethanol production was achieved via the sequential saccharification and fermentation of dilute sodium hydroxide (2% w/w NaOH in corn stover) treated corn stover using P. chrysosporium and G. trabeum . Ethanol production peaked on day 3 and day 4 for the samples inoculated with either P. chrysosporium or G. trabeum, slightly plateauing or decreasing thereafter. Ethanol production was highest for the combination of G. trabeum and E. coli K011 at 6.68 g/100 g corn stover, followed by the combination of P. chrysosporium and E. coli K011 at 5.00 g/100 g corn stover. Combination of both the fungi with S. cerevisiae generally had lower ethanol yields, ranging between 2.88 g (P. chrysosporium treated corn stover) and 3.09 g/100 g corn stover (G. trabeum treated corn stover). Acetic acid production ranged between 0.53 g and 2.03 g/100 g corn stover for the samples under different fungal treatments, while lactic acid production was only detected in samples treated with G. trabeum, throughout the 5 days of SSF.;The results of our study indicated that mild alkaline pretreatment coupled with fungal saccharification offer a promising bioprocess for ethanol production from corn stover without the addition of commercial enzymes. We believe these sequential procedures are potentially applicable to various other lignocellulosic materials (i.e. switchgrass, poplar, corn cobs) and may assist in environmentally, economical and technological friendlier ethanol production processes. (Abstract shortened by UMI.)
机译：我们旨在开发一种顺序生物过程，将纤维素材料转化为可发酵的糖，最终将乙醇用作运输燃料。我们在环境条件下进行了固态发酵，以诱导来自三种真菌物种，即Phanerochaete chrysosporium，Gloeophyllum trabeum和里氏木霉的木质纤维素分解活性。我们在纯纤维素和玉米秸秆上培养了每种真菌种类，以通过固态发酵几天来诱导纤维素酶，半纤维素酶和木质素分解酶的分泌。玉米秸秆被选为主要原料，因为它是最丰富的农业残留物之一。霉菌介导的过程释放出简单的碳水化合物，这是下游微生物利用的合适底物。接下来，我们对纤维素材料进行了同时的糖化和发酵（SSF）以产生更多的糖，然后将其转化为乙醇。;在玉米秸秆上进行SSF研究之前，我们首先在纯纤维素上对这些真菌种类进行了酶促研究，以评估它们的原位酶产生和水解能力。根据几项先前报道的研究的建议，滤纸用于筛选。将真菌物质对过滤器进行糖化的效率与低剂量（25 FPU / g纤维素）的商业纤维素酶进行了比较。结果表明，将滤纸糖化最有效的真菌种类是里氏木霉，在第5天产生5.13 g / 100 g乙醇滤纸，然后在1.79 g / 100 g滤纸上接种金黄色葡萄球菌。在整个五天的发酵阶段中，从用小白曲霉处理过的滤纸中未产生乙醇。在第5天，仅在用里氏木霉和市售酶处理过的样品中产生乙酸，浓度分别为0.95 g和2.57 g / 100 g滤纸；然后，我们用金孢假单胞菌进行了玉米秸秆的酶促糖化。和G. trabeum。通过使用啤酒酵母和大肠杆菌K011，将糖化产物随后发酵为乙醇。在啤酒酵母或大肠杆菌的SSF期间，接种金黄色葡萄球菌或小白球菌的所有样品在第4天的乙醇产量最高。对于用金黄色葡萄球菌处理的玉米秸秆，接种啤酒酵母的样品的玉米秸秆转化为乙醇的转化率为2.29 g / 100 g玉米秸秆，而对于接种大肠杆菌K011的样品，乙醇浓度为4.14克/ 100克玉米秸秆。对于用葡萄球菌处理过的玉米秸秆而言，接种啤酒酵母和大肠杆菌K011的样品的玉米秸秆转化为乙醇的转化率分别为1.90 g和4.79 g / 100 g玉米秸秆。在我们的研究中，我们进一步探索了玉米秸秆中温和化学药品（稀NaOH）与生物预处理和糖化的耦合。乙醇的生产是通过使用金黄色葡萄球菌（P. chrysosporium）和小球菌（G. trabeum）对糖化的稀氢氧化钠（玉米秸秆中2％w / w NaOH）进行顺序糖化和发酵来实现的。接种金黄色葡萄球菌或小球菌的样品的乙醇产量在第3天和第4天达到峰值，此后略有平稳或下降。在6.68 g / 100 g玉米秸秆中，小白曲霉和大肠杆菌K011的乙醇产量最高，其次在5.00 g / 100 g玉米秸秆中，金黄色葡萄球菌和大肠杆菌K011的乙醇产量最高。两种真菌与酿酒酵母的组合通常具有较低的乙醇产量，范围为2.88g（经金黄色葡萄球菌处理的玉米秸秆）和3.09g / 100g的玉米秸秆（G.trabeum处理的玉米秸秆）。在不同的真菌处理条件下，样品的乙酸产量范围为0.53 g至2.03 g / 100 g玉米秸秆，而在整个SSF的5天中，仅在用小梁茶处理过的样品中检测到了乳酸产量。研究表明，温和的碱性预处理与真菌糖化相结合，为玉米秸秆生产乙醇而无需添加商业酶提供了一种有前途的生物工艺。我们认为这些顺序的程序可能适用于其他各种木质纤维素材料（如柳枝,、杨木，玉米芯），并可能有助于环境，经济和技术上更友好的乙醇生产过程。 （摘要由UMI缩短。）

著录项

  • 作者

    Vincent, Micky Anak.;

  • 作者单位

    Iowa State University.;

  • 授予单位 Iowa State University.;
  • 学科 Alternative Energy.;Biology Microbiology.;Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 233 p.
  • 总页数 233
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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