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题名	秸秆汽爆分级及其发酵黄原胶的研究
作者	张志国
学位类别	博士
答辩日期	2010-05-27
授予单位	中国科学院研究生院
授予地点	北京
导师	陈洪章
关键词	秸秆 汽爆 黄原胶 惰性载体固态发酵 压力脉动
其他题名	Straw fraction by steam explosion and xanthan production
学位专业	生物化工
中文摘要	秸秆是储量丰富的可再生资源，将秸秆降解用于发酵大宗化学品对于减少石化资源使用和保障粮食安全具有重要意义，克服秸秆发酵大宗化学品的技术障碍和经济瓶颈使其实现产业化是目前面临的迫切任务。基于此，本论文首先研究了秸秆汽爆和水流筛分组合处理的分级方法，其次探索秸秆酶解液发酵黄原胶的可行性，最后选用惰性载体固态发酵方式生产黄原胶。通过上述研究得到以下结果： 1）建立了汽爆和水流筛分组合处理的秸秆分级方法，其筛分得到的纤维细胞、杂细胞分别占总量的47.6%和19.9%。分析两者化学组成、形态和酶解性质显示，杂细胞可在1: 3的高固液比条件下酶解，酶解液糖浓度达到81.99 g L-1，直接满足了发酵所需高糖浓度的要求；而纤维细胞难以在高固液比酶解，在1: 20下酶解率仅为42.61%。上述结果说明麦草汽爆分级和分别利用是实现秸秆高值化的有效途径。 2）建立了汽爆秸秆酶解液发酵黄原胶的工艺系统。首先研究了野油菜黄单胞菌对汽爆所产生抑制成分的敏感性以及这些物质的脱除方法。结果表明弱酸、呋喃衍生物和酚类物质都对黄原胶发酵有抑制作用。相近的汽爆强度下，使用低压和长维持时间的组合可以有效减少抑制物的生成量。1.3MPa、8 min汽爆条件下（R0=7552）的糠醛、5-羟甲基糠醛、酚类物质产生量比1.4MPa、6 min（R0=7787）条件下分别低37.1%、37.8%和20.6%；新生磷酸钙絮凝可以去除30%的酚类物质，汽爆秸秆风干处理可以去除78.3%的甲酸，94.5%的糠醛和88.8%的羟甲基糠醛。在脱除抑制成分的基础上优化了酶解液发酵黄原胶的培养基，其产量达到20.7 g L-1，碳源转化率达到0.62 g g-1。最后探索了木糖存在对发酵的影响。结果表明，X. campestris利用木糖能力很弱（消耗速率0.053~0.060 g L-1 h-1），木糖比例大于50%还会抑制其生长，但少量的木糖的存在（总糖的10%）可以提高黄原胶的分子量和侧链上乙酰基团、丙酮酰基团的含量，有提高产物品质作用。 3）针对液态发酵黄原胶发酵液粘度大，难以实现高浓度发酵的问题，选用惰性载体固态发酵技术生产黄原胶，并对其发酵过程进行了动力学表征。结果显示在0.5 cm立方体颗粒聚氨酯树脂载体，固液比1: 15（w: w）以及4.5 cm堆料厚度条件下，惰性载体固态发酵黄原胶浓度达到38.65 g L-1，是相应液态发酵产量的1.8倍。进一步分析比较静态固态发酵和压力脉动固态发酵方式对惰性吸附载体固态发酵黄原胶的影响，发现压力脉动方式能提高黄原胶发酵水平，使其产物浓度达到42.62 g L-1。 4. 建立了近红外光谱快速分析黄原胶固态发酵样品的方法。模型的外部验证显示，黄原胶浓度和生物量浓度的预测均方差分别为0.5597 g L-1和0.1692 g L-1。说明近红外光谱技术能够满足黄原胶固态发酵过程分析快速、准确的要求，为固态发酵提供了一种简便的分析方法。
英文摘要	Straw is a regenerative resource with abundant reserves. Using straw to build sugar platform and transforming its hydrolysates into bulk chemicals are important way to deal with petrochemical resource depletion and ensure food security. In this study, wheat straw was detached by steam-exploded treatment and water filtration, the feasibility of xanthan production by fermentation of wheat straw hydrolysate was investigated and then solid-state fermentation on inert carrier was chosen to produce xanthan. The main research contents and results of this dissertation are as follows: 1) Straw was treated by steam explosion and water filtration to detach the fibers and miscellaneous cells. The proportions of fibers and miscellaneous cells in exploded wheat straw were 47.6%, 19.9%, respectively. The morphology, chemical composition and degradability of fibers and miscellaneous cells were quite different. Miscellaneous cells were hydrolyzed at high-solid-liquid ratio (1: 3) and the sugar concentration of hydrolyzate reached 81.99 g L-1, which was conducive to industrial applications. The fibers had higher cellulose content (57.16%) but lower enzymolysis rate (42.61%) when the solid-liquid ratio was 1: 20. These results suggested that fraction and water filtration were effective for straw high-value utility. 2）The process of using steam-exploded straw hydrolysate to produce xanthan was established. Weak acids, furan derivatives and phenolic substances in the hydrolysate inhibited the growth of Xanthomonas campestris and the generation of xanthan. When the exploded intensity was similar, derived inhibitors under low pressure and long maintaining time were much less than those under high pressure and short maintaining time. For example, when the pressure and maintaining time were1.3 MPa and 12 min (R0=7552), the amounts of furfural, 5-hydroxymethylfurfural and phenolic substances were 37.1%, 37.8% and 20.6% less than those respectively when the pressure and maintaining time were 1.4 MPa and 10 min (R0=7787). Calcium phosphate flocculation was used to remove 30% phenolic substances and 78.3% fomic acid, 94.5% furfural and 88.8% 5-hydroxymethylfurfural were removed by air drying. After detoxification, the hydrolysate was used in xanthan production. Using the optimized media, xanthan production reached 20.7 g L-1, when the transfermation rate of sugar was 0.62 g g-1. The effect of xylose on X. campestris growth, xanthan generation and xanthan structure were also studied. X. campestris has a weak ability of metabolizing xylose (consumption rate was about 0.053~0.060 g L-1 h-1), when the ratio of xylose was more than 50%, the growth of the microorganism was mainly inhibited. However, the presence of a small amount of xylose (10%) could increase the molecular weight of xanthan gum and the content of acetyl and pyruvoyl group in side chain, improving the quality of xanthan. 3）Solid-state fermentation on polyurethane foam enhanced xanthan production. Under the optimized conditions (0.5-cm (side length) PUF cubes, 1: 15 of solid-liquid ratio and 4.5 cm bed depth), when glucose concentration was 80 g L-1, the final gum concentration in SSF were 38.65 g L-1, which was 1.8 times of that obtained in submerged fermentation. If air pressure pulsation was performed, the xanthan production was further increased and reached 42.62 g L-1. 4）A near-infrared spectroscopy method was established for rapid analysis of solid-state fermentation samples. The results of validation showed that the root mean square errors of pridiction of xanthan and biomass were 0.5597 and 0.1692 g L-1 respectively. It was suggested that NIRS was a simple, quick and accurate method for the monitor of xanthan production under solid state fermentation.
公开日期	2013-09-17
页码	139
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1527]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	张志国. 秸秆汽爆分级及其发酵黄原胶的研究[D]. 北京. 中国科学院研究生院. 2010.

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