Meyerozyma guilliermondii, a non-conventional yeast that naturally assimilates xylose, is considered as a candidate for biotechnological production of the sugar alternative xylitol. Because the genes of the xylose metabolism were yet unknown, all efforts published so far to increase the xylitol yield of this yeast are limited to fermentation optimization. Hence, this study aimed to genetically engineer this organism for the first time with the objective to increase xylitol production. Therefore, the previously uncharacterized genes of M. guilliermondii ATCC 6260 encoding for xylose reductase (XR) and xylitol dehydrogenase (XDH) were identified by pathway investigations and sequence similarity analysis. Cloning and overexpression of the putative XR as well as knockout of the putative XDH genes generated strains with about threefold increased xylitol yield. Strains that combined both genetic modifications displayed fivefold increase in overall xylitol yield. Enzymatic activity assays with lysates of XR overexpressing and XDH knockout strains underlined the presumed functions of the respective genes. Furthermore, growth evaluation of the engineered strains on xylose as sole carbon source provides insights into xylose metabolism and its utilization for cell growth.

中文翻译：

---

鉴定与古细菌耶尔森氏木糖代谢有关的基因及其遗传工程，以提高木糖醇的产量。

Meererozyma guilliermondii是一种自然吸收木糖的非常规酵母，被认为是糖替代木糖醇生物技术生产的候选产品。由于木糖代谢的基因尚不清楚，因此，迄今为止为提高该酵母的木糖醇产量而发表的所有努力仅限于发酵优化。因此，本研究旨在首次对该生物进行基因工程改造，目的是增加木糖醇的产量。因此，通过途径研究和序列相似性分析鉴定了编码木糖还原酶（XR）和木糖醇脱氢酶（XDH）的吉利蒙德氏杆菌ATCC 6260先前未鉴定的基因。推定的XR的克隆和过表达以及推定的XDH基因的敲除产生了木糖醇产率提高约三倍的菌株。结合了两种遗传修饰的菌株显示出木糖醇总产量增加了五倍。XR过表达和XDH敲除菌株的裂解物的酶活性测定强调了各个基因的推测功能。此外，对工程菌株以木糖作为唯一碳源的生长评估提供了对木糖代谢及其在细胞生长中利用的见解。