The Japan Association of Rural Resource Recycling Solutions (JARUS), 5-34-4 Shinbashi, Minato-ku, Tokyo 105-0004, Japan.
J Biosci Bioeng. 2011 Mar;111(3):320-5. doi: 10.1016/j.jbiosc.2010.11.003. Epub 2010 Dec 15.
Silage production from rice straw and whole-plant forage paddy rice is increasing in Japan because of decrease in rice consumption. One potential use for this silage is bioethanol production. In this study, we analyzed the effectiveness of three different commercially available cellulases at saccharification of sun-dried rice straw, ensiled rice straw, and rice whole-crop silage (WCS). Furthermore, the ethanol productivity of the simultaneous saccharification and ethanol fermentation process (SSF) from the same plant substrates was analyzed. Among the three kinds of cellulases tested (Novozymes NS50013, Genencor GC220, and Acremonium cellulase), Acremonium cellulase showed the highest ethanol production for the three plant substrates, and the WCS produced the highest ethanol level. Analysis of the enzymatic degradation activity of the cellulases revealed that Acremonium cellulase contained remarkably high glucoamylase and pectinase side activities relative to the other cellulase preparations. The addition of glucoamylase and pectinase to the other two cellulases significantly increased ethanol productivity to levels observed for the Acremonium cellulase preparation, which showed little enhanced performance with the addition of the same enzymes. Finally, we tested whether milling and sterilization had an effect on ethanol production and found that sterilized silage produced higher ethanol levels but that the milling process had no significant effect. These results show that (i) silage made from whole-plant rice can be used for bioethanol production and (ii) the proper selection and combination of commercially available enzymes can make SSF more cost efficient by removing the need for a pre-treatment step.
由于日本国内大米食用量减少，利用稻草和整株水稻生产青贮饲料的情况日渐增多。这种青贮饲料的一个潜在用途是生产生物乙醇。本研究分析了 3 种市售纤维素酶对晒干稻草、青贮稻草和水稻全株青贮料（WCS）糖化的效果。此外，还分析了利用同一植物原料进行同步糖化和发酵（SSF）过程的乙醇生产效率。在所测试的 3 种纤维素酶（诺维信 NS50013、杰能科 GC220 和枝顶孢霉纤维素酶）中，枝顶孢霉纤维素酶对 3 种植物原料显示出最高的乙醇产量，而 WCS 产生的乙醇水平最高。对纤维素酶的酶解活性分析表明，与其他纤维素酶制剂相比，枝顶孢霉纤维素酶含有显著较高的糖化酶和果胶酶侧活力。向另外两种纤维素酶中添加糖化酶和果胶酶可显著提高乙醇生产效率，达到与枝顶孢霉纤维素酶制剂相同的水平，而向后者中添加相同的酶则几乎没有提高性能。最后，我们测试了粉碎和灭菌是否会影响乙醇生产，发现灭菌青贮料可产生更高的乙醇水平，但粉碎过程没有显著影响。这些结果表明：（i）整株水稻青贮料可用于生物乙醇生产；（ii）通过选择和组合市售酶，可以避免预处理步骤，从而降低 SSF 的成本。
