Faculty of Science, University of Copenhagen, Rolighedsvej 23, Frederiksberg, Denmark.
Biotechnol Bioeng. 2014 Jan;111(1):59-68. doi: 10.1002/bit.25098. Epub 2013 Sep 11.
Production of ethanol from lignocellulosic materials has a promising market potential, but the process is still only at pilot/demonstration scale due to the technical and economical difficulties of the process. Operating the process at very high solids concentrations (above 20% dry matter-DM) has proven essential for economic feasibility at industrial scale. Historically, simultaneous saccharification and fermentation (SSF) was found to give better ethanol yields compared to separate hydrolysis and fermentation (SHF), but data in literature are typically based on operating the process at low dry matter conditions. In this work the impact of selected enzyme preparation and processing strategy (SHF, presaccharification and simultaneous saccharification and fermentation-PSSF, and SSF) on final ethanol yield and overall performance was investigated with pretreated wheat straw up to 30% DM. The experiments revealed that an SSF strategy was indeed better than SHF when applying an older generation enzyme cocktail (Celluclast-Novozym 188). In case of the newer product Cellic CTec 2, SHF resulted in 20% higher final ethanol yield compared to SSF. It was possible to close the mass balance around cellulose to around 94%, revealing that the most relevant products could be accounted for. One observation was the presence of oxidized sugar (gluconic acid) upon enzymatic hydrolysis with the latest enzyme preparation. Experiments showed gluconic acid formation by recently discovered enzymatic class of lytic polysaccharides monoxygenases (LPMO's) to be depending on the processing strategy. The lowest concentration was achieved in SSF, which could be correlated with less available oxygen due to simultaneous oxygen consumption by the yeast. Quantity of glycerol and cell mass was also depending on the selected processing strategy.
从木质纤维素原料生产乙醇具有广阔的市场潜力，但由于该过程的技术和经济困难，该过程仍仅处于中试/示范规模。在非常高的固体浓度（高于 20%干物质-DM）下操作该过程已被证明对于工业规模的经济可行性至关重要。从历史上看，与单独的水解和发酵（SHF）相比，同时糖化和发酵（SSF）被发现可获得更好的乙醇产率，但文献中的数据通常基于在低干物质条件下操作该过程。在这项工作中，研究了选定的酶制剂和加工策略（SHF、预糖化和同时糖化和发酵-PSSF、SSF）对预处理小麦秸秆高达 30% DM 的最终乙醇产率和整体性能的影响。实验表明，当应用较旧一代酶混合物（Celluclast-Novozym 188）时，SSF 策略确实优于 SHF。对于较新的产品 Cellic CTec 2，与 SSF 相比，SHF 可使最终乙醇产率提高 20%。可以将纤维素的质量平衡封闭在 94%左右，这表明可以解释最相关的产物。一个观察结果是，在使用最新的酶制剂进行酶解时存在氧化糖（葡萄糖酸）。实验表明，糖基水解酶类氧化还原酶（LPMO）最近发现的酶类的葡萄糖酸形成取决于加工策略。在 SSF 中达到最低浓度，这可以与由于酵母同时消耗氧气而导致的同时氧气消耗有关。甘油和细胞质量的数量也取决于所选的加工策略。
