Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501, Japan.
J Biotechnol. 2012 Apr 30;158(4):203-10. doi: 10.1016/j.jbiotec.2011.06.025. Epub 2011 Jun 29.
The cost of the lignocellulose-hydrolyzing enzymes used in the saccharification process of ethanol production from biomass accounts for a relatively high proportion of total processing costs. Cell surface engineering technology has facilitated a reduction in these costs by integrating saccharification and fermentation processes into a recombinant microbe strain expressing heterologous enzymes on the cell surface. We constructed a recombinant Saccharomyces cerevisiae that not only hydrolyzed hemicelluloses by codisplaying endoxylanase from Trichoderma reesei, β-xylosidase from Aspergillus oryzae, and β-glucosidase from Aspergillus aculeatus but that also assimilated xylose through the expression of xylose reductase and xylitol dehydrogenase from Pichia stipitis and xylulokinase from S. cerevisiae. The recombinant strain successfully produced ethanol from rice straw hydrolysate consisting of hemicellulosic material containing xylan, xylooligosaccharides, and cellooligosaccharides without requiring the addition of sugar-hydrolyzing enzymes or detoxication. The ethanol titer of the strain was 8.2g/l after 72h fermentation, which was approximately 2.5-fold higher than that of the control strain. The yield (grams of ethanol per gram of total sugars in rice straw hydrolysate consumed) was 0.41g/g, which corresponded to 82% of the theoretical yield. The cell surface-engineered strain was thus highly effective for consolidating the process of ethanol production from hemicellulosic materials.
用于生物质乙醇生产糖化过程中木质纤维素水解酶的成本占总加工成本的相对较高比例。细胞表面工程技术通过将糖化和发酵过程整合到表达细胞表面异源酶的重组微生物菌株中,降低了这些成本。我们构建了一种重组酿酒酵母,该酵母不仅通过共表达里氏木霉的内切木聚糖酶、米曲霉的β-木糖苷酶和棘孢曲霉的β-葡萄糖苷酶来水解半纤维素,还通过表达毕赤酵母的木糖还原酶和木酮糖激酶以及酿酒酵母的木糖脱氢酶来同化木糖。重组菌株成功地从由含有木聚糖、木二糖和纤维二糖的半纤维素材料组成的水稻秸秆水解物中生产乙醇,而无需添加糖水解酶或解毒。该菌株在 72 小时发酵后,乙醇浓度达到 8.2g/L,比对照菌株高约 2.5 倍。该菌株的得率(每消耗 1 克水稻秸秆水解物中的总糖产生的克乙醇)为 0.41g/g,相当于理论得率的 82%。因此,该细胞表面工程菌株在整合从半纤维素材料生产乙醇的过程中非常有效。