Cellulose is the major constitute of plant biomass and highly available in agricultural wastes and industrial effluents, thereby being a cost-effective feedstock for bioenergy production. However, most hydrogen producing bacteria (HPB) could not directly convert cellulosic materials (such as rice husk and rice straw) into hydrogen whereas most HPB could utilize sugar and starch for hydrogen production. In this work, we used an indigenous bacterial isolate Clostridium butyricum CGS2 as HPB, which could directly convert soluble starch into H2 with a maximum H2 production rate and a H2 yield of 205.07 ml H2/h/l and 6.46 mmol H2/g starch, respectively. However, C. butyricum CGS2 could not ferment pure cellulosic materials such as carboxymethyl cellulose and xylan. Moreover, we found that C. butyricum CGS2 could utilize rich husk to produce H2 at a rate of 13.19 ml H2/h/l due to the starch content in rice husk (H2 yield = 1.49 mmol H2/g rice husk). In contrast, since lacking starch content, rice straw cannot be converted to H2 by C. butyricum CGS2. The foregoing results suggest that increasing the starch content in the natural agricultural wastes may make them better feedstock for fermentative H2 production. Hence, a genetically modified plant (Arabidopsis vacuolar) was constructed to enhance its starch concentration. The starch concentration of mutant plant S1 increased to 10.67 mg/fresh weight, which is four times higher than that of wild type plant. Using mutant plant S1 as carbon source, C. butyricum CGS2 was able to give a high cumulative H2 production and H2 production rate of 285.4 ml H2/l and 43.6 ml/h/l, respectively. The cumulative H2 production and H2 production rate both increased when the concentration of the transgenic plant was increased. Therefore, this study successful demonstrated the feasibility of expressing starch on genetically-modified plants to create a more effective feedstock for dark H2 fermentation.
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机译：纤维素是植物生物质的主要组成部分，在农业废料和工业废水中高度可用，因此是生产生物能源的经济有效的原料。但是，大多数产氢细菌（HPB）不能直接将纤维素材料（例如稻壳和稻草）转化为氢，而大多数HPB可以利用糖和淀粉来生产氢。在这项工作中，我们使用了本地分离的细菌丁酸梭菌CGS2作为HPB，它可以将可溶性淀粉直接转化为H2，具有最高的H2产生率，H2产量为205.07 ml H2 / h / l和6.46 mmol H2 / g淀粉，分别。然而，丁酸梭菌CGS2不能发酵纯纤维素材料，例如羧甲基纤维素和木聚糖。此外，由于稻壳中的淀粉含量（H2产量= 1.49 mmol H2 / g稻壳），我们发现酪酸梭菌CGS2可以利用丰富的稻壳以13.19 ml H2 / h / l的速率生产H2。相反，由于缺乏淀粉含量，稻草不能被丁酸梭菌CGS2转化为H 2。前述结果表明，增加天然农业废料中的淀粉含量可能使它们成为发酵H2生产的较好原料。因此，构建了转基因植物（拟南芥）以提高其淀粉浓度。突变植物S1的淀粉浓度增加到10.67 mg /鲜重，是野生型植物的四倍。使用突变植物S1作为碳源，丁酸梭菌CGS2能够分别产生285.4 ml H2 / l和43.6 ml / h / l的高累积H2产生量和H2产生量。当转基因植物的浓度增加时，累积的H 2产生和H 2产生速率均增加。因此，这项研究成功地证明了在转基因植物上表达淀粉以创建更有效的深色H2发酵原料的可行性。
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