National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan.
National Institute of Livestock and Grassland Science, Nasushiobara, Tochigi 329-2793, Japan.
Biotechnol Biofuels. 2011 Nov 1;4:46. doi: 10.1186/1754-6834-4-46.
In the normal process of bioethanol production, biomass is transported to integrated large factories for degradation to sugar, fermentation, and recovery of ethanol by distillation. Biomass nutrient loss occurs during preservation and degradation. Our aim was to develop a decentralized ethanol production system appropriate for farm or co-operative level production that uses a solid-state fermentation method for producing bio-ethanol from whole crops, provides cattle feed, and produces no wastes. The idea is to incorporate traditional silage methods with simultaneous saccharification and fermentation. Harvested, fresh biomass is ensiled with biomass-degrading enzymes and yeast. Multiple parallel reactions for biomass degradation and ethanol and lactic acid production are induced in solid culture in hermetically sealed containers at a ranch. After fermentation, ethanol is collected on site from the vapor from heated fermented products.
The parallel reactions of simultaneous saccharification and fermentation were induced efficiently in the model fermentation system. In a laboratory-scale feasibility study of the process, 250 g of freshly harvested forage rice with 62% moisture was treated with 0.86 filter paper units/g dry matter (DM) of cellulase and 0.32 U/g DM of glucoamylase. After 20 days of incubation at 28°C, 6.4 wt.% of ethanol in fresh matter (equivalent to 169 g/kg DM) was produced. When the 46 wt.% moisture was gathered as vapor from the fermented product, 74% of the produced ethanol was collected. Organic cellular contents (such as the amylase and pronase degradable fractions) were decreased by 63% and organic cell wall (fiber) content by 7% compared to silage prepared from the same material.
We confirmed that efficient ethanol production is induced in nonsterilized whole rice plants in a laboratory-scale solid-state fermentation system. For practical use of the method, further study is needed to scale-up the fermentation volume, develop an efficient ethanol recovery method, and evaluate the fermentation residue as an actual cattle feed.
在正常的生物乙醇生产过程中，生物质被运送到综合大型工厂，通过降解为糖、发酵和蒸馏回收乙醇。生物质在保存和降解过程中会发生营养损失。我们的目标是开发一种适用于农场或合作社生产的分散式乙醇生产系统，该系统使用固态发酵方法从整个作物中生产生物乙醇，提供牛饲料，并且不产生废物。该方法是将传统青贮方法与同步糖化和发酵相结合。收获的新鲜生物质与生物质降解酶和酵母一起青贮。在牧场的密封容器中，固态培养物中诱导了多个用于生物质降解和乙醇和乳酸生产的平行反应。发酵后，从加热发酵产品的蒸汽中现场收集乙醇。
在模型发酵系统中有效地诱导了同步糖化和发酵的平行反应。在该过程的实验室规模可行性研究中，用 0.86 滤纸单位/干物质（DM）的纤维素酶和 0.32 U/g DM 的糖化酶处理 250 g 水分含量为 62%的新鲜饲料稻。在 28°C 下孵育 20 天后，新鲜物质中产生了 6.4 wt.%的乙醇（相当于 169 g/kg DM）。当 46 wt.%的水分从发酵产物中以蒸汽形式收集时，收集到的乙醇产量为 74%。与用相同材料制备的青贮饲料相比，有机细胞内容物（如淀粉酶和蛋白酶可降解部分）减少了 63%，有机细胞壁（纤维）含量减少了 7%。
我们证实，在实验室规模的固态发酵系统中，未经灭菌的整株水稻可以有效地诱导乙醇生产。为了实际应用该方法，需要进一步研究发酵体积的放大、开发有效的乙醇回收方法，并评估发酵残渣作为实际牛饲料的用途。
