Comparative ethanol productivities of different Zymomonas recombinants fermenting oat hull hydrolysate
Comparative ethanol productivities of different Zymomonas recombinants fermenting oat hull hydrolysate
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DOI：
10.1385/abab:91-93:1-9:133
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发表时间：
2001-03-01
影响因子：
3
通讯作者：
Tolan, JS
中科院分区：
文献类型：
--
作者：
Lawford, HG;Rousseau, JD;Tolan, JS
加拿大渥太华的Iogen公司最近在其酶生产设施附近建造了一个50吨/天的生物质制乙醇示范工厂。Iogen与多伦多大学合作，利用其生物质水解物测试了国家可再生能源实验室代谢工程的活动酵母菌的C6/C5共发酵性能特征。在本研究中，生物质原料是一种农业废弃物，即燕麦壳，通过专有的两阶段工艺进行水解，其中包括200-250度的稀硫酸预处理，然后是纤维素酶水解。燕麦壳水解液（OHH）含有葡萄糖、木糖和阿拉伯糖，质量比约为8:3:0.5。发酵培养基由稀释的水解液制备，加入2.5 mL/L的玉米浆（50%固体）和1.2 g/L的磷酸二铵进行营养修饰。使用这种最低水平的营养补充进行大规模乙醇生产的估计成本为每加仑乙醇4.4美分。本研究考察了利用木糖、耐四环素、携带质粒、获得专利的重组Z. mobilis培养物：CP4:pZB5、ZM4:pZB5、39676:pZB4L，以及一种适应硬木预水解的39676:pZB4L（称为“适应”菌株）的生长和发酵性能。在含有6% （w/v）葡萄糖、3%木糖和0.75%醋酸的无条件OHH条件下，发酵时间为30 h时，rec Zm ZM4:pZB5的发酵效果最好，发酵时间为48 h时，CP4:pZB5的发酵效果次之，相应的容积率分别为1.4和0.89 g/(L.h)。以有效葡萄糖和木糖为基础，两菌株的工艺乙醇收率均为0.47 g/g（转化率为92%）。48h时，rec Zm 39676:pZB4L和适应菌株的产率分别为0.32和0.34 g/g。试验菌株都不能发酵阿拉伯糖。醋酸耐受性似乎是共发酵性能的主要决定因素。
Iogen Corporation of Ottawa, Canada, has recently built a 50 t/d biomass-to-ethanol demonstration plant adjacent to its enzyme production facility. Iogen has partnered with the University of Toronto to test the C6/C5 cofermentation performance characteristics of National Renewable Energy Laboratory's metabolically engineered Zymomonas mobilis using its biomass hydrolysates. In this study, the biomass feedstock was an agricultural waste, namely oat hulls, which was hydrolyzed in a proprietary two-stage process involving pretreatment with dilute sulfuric acid at 200-250 degreesC, followed by cellulase hydrolysis. The oat hull hydrolysate (OHH) contained glucose, xylose, and arabinose in a mass ratio of about 8:3:0.5. Fermentation media, prepared from diluted hydrolysate, were nutritionally amended with 2.5 mL/L of corn steep liquor (50% solids) and 1.2 g/L of diammonium phosphate. The estimated cost for large-scale ethanol production using this minimal level of nutrient supplementation was 4.4 cent /gal of ethanol. This work examined the growth and fermentation performance of xylose-utilizing, tetracycline-resistant, plasmid-bearing, patented, recombinant Z. mobilis cultures: CP4:pZB5, ZM4:pZB5, 39676:pZB4L, and a hardwood prehydrolysate-adapted variant of 39676:pZB4L (designated as the "adapted" strain). In pi-I-stat batch fermentations with unconditioned OHH containing 6% (w/v) glucose, 3% xylose, and 0.75% acetic acid, rec Zm ZM4:pZB5 gave the best performance with a fermentation time of 30 h, followed by CP4:pZB5 at 48 h, with corresponding volumetric productivities of 1.4 and 0.89 g/(L.h), respectively. Based on the available glucose and xylose, the process ethanol yield for both strains was 0.47 g/g (92% conversion efficiency). At 48 h, the process yield for rec Zm 39676:pZB4L and the adapted strain was 0.32 and 0.34 g/g, respectively. None of the test strains was able to ferment arabinose. Acetic acid tolerance appeared to be a major determining factor in cofermentation performance.