Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA 50011, USA.
Bioprocess Biosyst Eng. 2012 Jan;35(1-2):99-104. doi: 10.1007/s00449-011-0617-9. Epub 2011 Sep 10.
A cascade type of fermentation, designated the cascade simultaneous saccharification and fermentation (CSSF), was studied to convert corn stover derived pentose and hexose to ethanol with reduced enzyme input. In detail, each step of CSSF utilizes two sequential SSF phases operating on pentose and hexose, i.e., pentose conversion using xylanase, endo-glucanase, and recombinant Escherichia coli (KO11) with minimal glucose conversion in the first phase SSF, and hexose conversion in the second phase SSF using cellulase, β-glucosidase, and Saccharomyces cerevisiae (D(5)A). In this cascade scheme, multiple stages of 1st and 2nd phase SSF were performed in series; enzymes are recycled from the fermentation broth of the last stage for the use of the next stage. This bioconversion process yielded up to 60% of the theoretical maximum ethanol yield based on the total sugars in untreated corn stover, while enzyme loadings were reduced by 50% (v/v) and the final ethanol concentration reached 27 g/l.
采用级联式发酵，即级联同步糖化发酵（CSSF），以降低酶用量将玉米秸秆中的戊糖和己糖转化为乙醇。详细来说，CSSF 的每一步都利用两个连续的 SSF 阶段来处理戊糖和己糖，即使用木聚糖酶、内切葡聚糖酶和重组大肠杆菌（KO11）在第一阶段 SSF 中进行戊糖转化，同时在第二阶段 SSF 中使用纤维素酶、β-葡萄糖苷酶和酿酒酵母（D(5)A）进行己糖转化，第一阶段和第二阶段 SSF 的多个阶段串联进行；酶从最后一个阶段的发酵液中回收，用于下一个阶段。在这个生物转化过程中，基于未处理玉米秸秆中的总糖，可达到理论最大乙醇产量的 60%，而酶用量减少了 50%（v/v），最终乙醇浓度达到 27g/L。
