Liu Zhuo, Ho Shih-Hsin, Sasaki Kengo, den Haan Riaan, Inokuma Kentaro, Ogino Chiaki, van Zyl Willem H, Hasunuma Tomohisa, Kondo Akihiko
Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan.
Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan.
Sci Rep. 2016 Apr 15;6:24550. doi: 10.1038/srep24550.
Cellulosic biofuel is the subject of increasing attention. The main obstacle toward its economic feasibility is the recalcitrance of lignocellulose requiring large amount of enzyme to break. Several engineered yeast strains have been developed with cellulolytic activities to reduce the need for enzyme addition, but exhibiting limited effect. Here, we report the successful engineering of a cellulose-adherent Saccharomyces cerevisiae displaying four different synergistic cellulases on the cell surface. The cellulase-displaying yeast strain exhibited clear cell-to-cellulose adhesion and a "tearing" cellulose degradation pattern; the adhesion ability correlated with enhanced surface area and roughness of the target cellulose fibers, resulting in higher hydrolysis efficiency. The engineered yeast directly produced ethanol from rice straw despite a more than 40% decrease in the required enzyme dosage for high-density fermentation. Thus, improved cell-to-cellulose interactions provided a novel strategy for increasing cellulose hydrolysis, suggesting a mechanism for promoting the feasibility of cellulosic biofuel production.
纤维素生物燃料正受到越来越多的关注。其经济可行性的主要障碍是木质纤维素的顽固性，需要大量酶来分解。已经开发了几种具有纤维素分解活性的工程酵母菌株，以减少酶添加的需求，但效果有限。在此，我们报告了一种成功构建的纤维素附着型酿酒酵母，其在细胞表面展示了四种不同的协同纤维素酶。展示纤维素酶的酵母菌株表现出明显的细胞与纤维素粘附以及“撕裂”纤维素降解模式；粘附能力与目标纤维素纤维表面积和粗糙度的增加相关，从而提高了水解效率。尽管高密度发酵所需的酶剂量减少了40%以上，但工程酵母仍能直接从稻草中生产乙醇。因此，改善细胞与纤维素的相互作用为提高纤维素水解提供了一种新策略，提示了一种促进纤维素生物燃料生产可行性的机制。
