Xylitol is a commercially important chemical with multiple applications in the food and pharmaceutical industries. According to the US Department of Energy, xylitol is one of the top twelve platform chemicals that can be produced from biomass. The chemical method for xylitol synthesis is however, expensive and energy intensive. In contrast, the biological route using microbial cell factories offers a potential cost-effective alternative process. The bioprocess occurs under ambient conditions and makes use of biocatalysts and biomass which can be sourced from renewable carbon originating from a variety of cheap waste feedstocks. In this study, biotransformation of xylose to xylitol was investigated using Yarrowia lipolytica, an oleaginous yeast which was firstly grown on a glycerol/glucose for screening of co-substrate, followed by media optimisation in shake flask, scale up in bioreactor and downstream processing of xylitol. A two-step medium optimization was employed using central composite design and artificial neural network coupled with genetic algorithm. The yeast amassed a concentration of 53.2 g/L xylitol using pure glycerol (PG) and xylose with a bioconversion yield of 0.97 g/g. Similar results were obtained when PG was substituted with crude glycerol (CG) from the biodiesel industry (titer: 50.5 g/L; yield: 0.92 g/g). Even when xylose from sugarcane bagasse hydrolysate was used as opposed to pure xylose, a xylitol yield of 0.54 g/g was achieved. Xylitol was successfully crystallized from PG/xylose and CG/xylose fermentation broths with a recovery of 39.5 and 35.3%, respectively. To the best of the author’s knowledge, this study demonstrates for the first time the potential of using Y. lipolytica as a microbial cell factory for xylitol synthesis from inexpensive feedstocks. The results obtained are competitive with other xylitol producing organisms.

中文翻译：

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产油酵母酵母解脂耶氏酵母将粗甘油和木糖生物价值转化为木糖醇。

木糖醇是一种重要的商业化学品，在食品和制药工业中有多种应用。根据美国能源部的数据，木糖醇是可以由生物质生产的十二种平台化学品之一。然而，用于木糖醇合成的化学方法昂贵且耗能。相反，使用微生物细胞工厂的生物途径提供了一种潜在的具有成本效益的替代方法。该生物过程在环境条件下发生，并利用了生物催化剂和生物质，这些生物催化剂和生物质可以来自各种廉价废物原料产生的可再生碳。在这项研究中，使用解脂耶氏酵母（Yarrowia lipolytica）研究了木糖向木糖醇的生物转化，这是一种油脂性酵母，首先在甘油/葡萄糖上生长以筛选共底物，然后在摇瓶中进行培养基优化，在生物反应器中扩大规模，并在木糖醇的下游进行处理。利用中央复合设计和人工神经网络结合遗传算法进行了两步介质优化。酵母使用纯甘油（PG）和木糖积累了53.2 g / L的木糖醇浓度，生物转化产量为0.97 g / g。当用生物柴油行业的粗甘油（CG）替代PG时，可获得相似的结果（滴定度：50.5 g / L；产率：0.92 g / g）。即使使用来自甘蔗渣水解物的木糖而不是纯木糖，木糖醇的产量也达到0.54g / g。木糖醇已成功从PG /木糖和CG /木糖发酵液中结晶，回收率分别为39.5％和35.3％。据作者所知，这项研究首次证明了将解脂耶氏酵母用作从廉价原料合成木糖醇的微生物细胞工厂的潜力。获得的结果与其他木糖醇生产生物竞争。