Background The search for sustainable energy sources has become a worldwide issue, making the development of efficient biofuel production processes a priority. Immobilization of second-generation (2G) xylose-fermenting Saccharomyces cerevisiae strains is a promising approach to achieve economic viability of 2G bioethanol production from undetoxified hydrolysates through operation at high cell load and mitigation of inhibitor toxicity. In addition, the use of a fixed-bed reactor can contribute to establish an efficient process because of its distinct advantages, such as high conversion rate per weight of biocatalyst and reuse of biocatalyst. Results This work assessed the influence of alginate entrapment on the tolerance of recombinant S. cerevisiae to acetic acid. Encapsulated GSE16-T18SI.1 (T18) yeast showed an outstanding performance in repeated batch fermentations with cell recycling in YPX medium supplemented with 8 g/L acetic acid (pH 5.2), achieving 10 cycles without significant loss of productivity. In the fixed-bed bioreactor, a high xylose fermentation rate with ethanol yield and productivity values of 0.38 gethanol/gsugars and 5.7 g/L/h, respectively were achieved in fermentations using undetoxified sugarcane bagasse hemicellulose hydrolysate, with and without medium recirculation. Conclusions The performance of recombinant strains developed for 2G ethanol production can be boosted strongly by cell immobilization in alginate gels. Yeast encapsulation allows conducting fermentations in repeated batch mode in fixed-bed bioreactors with high xylose assimilation rate and high ethanol productivity using undetoxified hemicellulose hydrolysate.

中文翻译：

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在固定床反应器中使用重组酿酒酵母的固定细胞重复批次作为从未解毒的半纤维素水解物中生产高 2G 乙醇的策略。

背景 寻找可持续能源已成为一个世界性的问题，使开发高效的生物燃料生产工艺成为优先事项。第二代 (2G) 木糖​​发酵酿酒酵母菌株的固定化是一种有前景的方法，可通过在高细胞负荷下操作和减轻抑制剂毒性来实现从未解毒的水解产物生产 2G 生物乙醇的经济可行性。此外，固定床反应器的使用有助于建立高效的工艺，因为它具有独特的优势，例如单位重量生物催化剂的高转化率和生物催化剂的重复利用。结果这项工作评估了藻酸盐包埋对重组酿酒酵母对乙酸的耐受性的影响。封装 GSE16-T18SI。1 (T18) 酵母在添加了 8 g/L 乙酸 (pH 5.2) 的 YPX 培养基中进行细胞循环重复分批发酵时表现出出色的性能，可实现 10 个循环而不会显着降低生产力。在固定床生物反应器中，使用未解毒的甘蔗渣半纤维素水解物进行发酵，在有和没有介质再循环的情况下，实现了高木糖发酵率，乙醇产率和产率分别为 0.38 g乙醇/gsugars 和 5.7 g/L/h。结论 为 2G 乙醇生产而开发的重组菌株的性能可以通过藻酸盐凝胶中的细胞固定而大大提高。