USDA Agricultural Research Service, National Center for Agricultural Utilization Research, Peoria, IL 61604, U.S.A.
Biochem J. 2012 Mar 1;442(2):241-52. doi: 10.1042/BJ20111922.
Conversion of plant cell walls to ethanol constitutes second generation bioethanol production. The process consists of several steps: biomass selection/genetic modification, physiochemical pretreatment, enzymatic saccharification, fermentation and separation. Ultimately, it is desirable to combine as many of the biochemical steps as possible in a single organism to achieve CBP (consolidated bioprocessing). A commercially ready CBP organism is currently unreported. Production of second generation bioethanol is hindered by economics, particularly in the cost of pretreatment (including waste management and solvent recovery), the cost of saccharification enzymes (particularly exocellulases and endocellulases displaying kcat ~1 s-1 on crystalline cellulose), and the inefficiency of co-fermentation of 5- and 6-carbon monosaccharides (owing in part to redox cofactor imbalances in Saccharomyces cerevisiae).
将植物细胞壁转化为乙醇构成第二代生物乙醇生产。该过程包括多个步骤：生物质选择/遗传修饰、理化预处理、酶解糖化、发酵和分离。最终，理想情况下，尽可能将多个生化步骤组合在单个生物体中，以实现 CBP（综合生物加工）。目前尚未报道具有商业应用前景的 CBP 生物体。第二代生物乙醇的生产受到经济性的阻碍，特别是预处理的成本（包括废物管理和溶剂回收）、糖化酶的成本（特别是外切纤维素酶和内切纤维素酶在结晶纤维素上的 kcat~1 s-1）以及 5-和 6-碳单糖的共发酵效率（部分原因是酿酒酵母中氧化还原辅因子失衡）。
