Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Nada, Kobe, Japan.
Biotechnol J. 2010 May;5(5):449-55. doi: 10.1002/biot.200900291.
We demonstrate direct ethanol fermentation from amorphous cellulose using cellulase-co-expressing yeast. Endoglucanases (EG) and cellobiohydrolases (CBH) from Trichoderma reesei, and beta-glucosidases (BGL) from Aspergillus aculeatus were integrated into genomes of the yeast strain Saccharomyces cerevisiae MT8-1. BGL was displayed on the yeast cell surface and both EG and CBH were secreted or displayed on the cell surface. All enzymes were successfully expressed on the cell surface or in culture supernatants in their active forms, and cellulose degradation was increased 3- to 5-fold by co-expressing EG and CBH. Direct ethanol fermentation from 10 g/L phosphoric acid swollen cellulose (PASC) was also carried out using EG-, CBH-, and BGL-co-expressing yeast. The ethanol yield was 2.1 g/L for EG-, CBH-, and BGL-displaying yeast, which was higher than that of EG- and CBH-secreting yeast (1.6 g/L ethanol). Our results show that cell surface display is more suitable for direct ethanol fermentation from cellulose.
我们使用表达纤维素酶的酵母演示了从无定形纤维素进行直接乙醇发酵。内切葡聚糖酶（EG）和纤维二糖水解酶（CBH）来自里氏木霉，β-葡萄糖苷酶（BGL）来自棘孢曲霉，被整合到酵母菌株酿酒酵母 MT8-1 的基因组中。BGL 被展示在酵母细胞表面上，而 EG 和 CBH 则被分泌或展示在细胞表面上。所有酶都以其活性形式成功地在细胞表面或培养上清液中表达，并且通过共表达 EG 和 CBH，纤维素降解增加了 3 到 5 倍。使用表达 EG、CBH 和 BGL 的酵母还进行了从 10 g/L 磷酸膨胀纤维素（PASC）进行直接乙醇发酵。EG、CBH 和 BGL 展示酵母的乙醇产量为 2.1 g/L，高于 EG 和 CBH 分泌酵母（1.6 g/L 乙醇）。我们的结果表明，细胞表面展示更适合从纤维素进行直接乙醇发酵。
