VTT Technical Research Centre of Finland, Tietotie 2, FI-02150 Espoo, Finland.
Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yajoi, Bunkyo, Tokyo 113-8657, Japan.
FEMS Yeast Res. 2020 May 1;20(3). doi: 10.1093/femsyr/foaa019.
Processed lignocellulosic biomass is a source of mixed sugars that can be used for microbial fermentation into fuels or higher value products, like chemicals. Previously, the yeast Saccharomyces cerevisiae was engineered to utilize its cellodextrins through the heterologous expression of sugar transporters together with an intracellular expressed β-glucosidase. In this study, we screened a selection of eight (putative) cellodextrin transporters from different yeast and fungal hosts in order to extend the catalogue of available cellobiose transporters for cellobiose fermentation in S. cerevisiae. We confirmed that several in silico predicted cellodextrin transporters from Aspergillus niger were capable of transporting cellobiose with low affinity. In addition, we found a novel cellobiose transporter from the yeast Lipomyces starkeyi, encoded by the gene Ls120451. This transporter allowed efficient growth on cellobiose, while it also grew on glucose and lactose, but not cellotriose nor cellotetraose. We characterized the transporter more in-depth together with the transporter CdtG from Penicillium oxalicum. CdtG showed to be slightly more efficient in cellobiose consumption than Ls120451 at concentrations below 1.0 g/L. Ls120451 was more efficient in cellobiose consumption at higher concentrations and strains expressing this transporter grew slightly slower, but produced up to 30% more ethanol than CdtG.
经过加工的木质纤维素生物质是一种混合糖的来源，可以用于微生物发酵成燃料或更高价值的产品，如化学品。以前，通过异源表达糖转运蛋白和细胞内表达的β-葡萄糖苷酶，对酵母酿酒酵母进行了工程改造，以利用其纤维二糖。在这项研究中，我们筛选了来自不同酵母和真菌宿主的 8 种（推定的）纤维二糖转运蛋白，以扩展可用于酿酒酵母纤维二糖发酵的可用纤维二糖转运蛋白目录。我们证实，来自黑曲霉的几种计算机预测纤维二糖转运蛋白能够以低亲和力转运纤维二糖。此外，我们从酵母石纹假丝酵母中发现了一种新型的纤维二糖转运蛋白，由基因 Ls120451 编码。该转运蛋白允许在纤维二糖上有效生长，同时也在葡萄糖和乳糖上生长，但不在纤维三糖和纤维四糖上生长。我们与来自草酸青霉的转运蛋白 CdtG 一起更深入地研究了这种转运蛋白。在低于 1.0 g/L 的浓度下，CdtG 在纤维二糖消耗方面的效率略高于 Ls120451。在较高浓度下，Ls120451 消耗纤维二糖的效率更高，并且表达这种转运蛋白的菌株生长速度略慢，但比 CdtG 多产生 30%的乙醇。
