Cagnin Lorenzo, Gronchi Nicoletta, Basaglia Marina, Favaro Lorenzo, Casella Sergio
Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova, Legnaro, Italy.
Front Microbiol. 2021 Nov 4;12:756032. doi: 10.3389/fmicb.2021.756032. eCollection 2021.
The production of lignocellulosic ethanol calls for a robust fermentative yeast able to tolerate a wide range of toxic molecules that occur in the pre-treated lignocellulose. The concentration of inhibitors varies according to the composition of the lignocellulosic material and the harshness of the pre-treatment used. It follows that the versatility of the yeast should be considered when selecting a robust strain. This work aimed at the validation of seven natural strains, previously selected for their industrial fitness, for their application in the production of lignocellulosic bioethanol. Their inhibitor resistance and fermentative performances were compared to those of the benchmark industrial yeast Ethanol Red, currently utilized in the second-generation ethanol plants. The yeast strains were characterized for their tolerance using a synthetic inhibitor mixture formulated with increasing concentrations of weak acids and furans, as well as steam-exploded lignocellulosic pre-hydrolysates, generally containing the same inhibitors. The eight non-diluted liquors have been adopted to assess yeast ability to withstand bioethanol industrial conditions. The most tolerant Fm17 strain, together with the reference Ethanol Red, was evaluated for fermentative performances in two pre-hydrolysates obtained from cardoon and common reed, chosen for their large inhibitor concentrations. Fm17 outperformed the industrial strain Ethanol Red, producing up to 18 and 39 g/L ethanol from cardoon and common reed, respectively, with ethanol yields always higher than those of the benchmark strain. This natural strain exhibits great potential to be used as superior yeast in the lignocellulosic ethanol plants.
木质纤维素乙醇的生产需要一种强大的发酵酵母，它能够耐受预处理木质纤维素中出现的多种有毒分子。抑制剂的浓度会根据木质纤维素材料的组成和所用预处理的严苛程度而有所不同。因此，在选择强大的酵母菌株时，应考虑酵母的多功能性。这项工作旨在验证七种先前因其工业适用性而被选中的天然菌株在木质纤维素生物乙醇生产中的应用。将它们的抗抑制剂能力和发酵性能与目前在第二代乙醇工厂中使用的基准工业酵母乙醇红进行了比较。使用由浓度不断增加的弱酸和呋喃以及蒸汽爆破木质纤维素预水解物配制的合成抑制剂混合物对酵母菌株的耐受性进行了表征，蒸汽爆破木质纤维素预水解物通常含有相同的抑制剂。采用这八种未稀释的溶液来评估酵母耐受生物乙醇工业条件的能力。对耐受性最强的Fm17菌株以及参考菌株乙醇红在从刺芹和芦苇中获得的两种预水解物中的发酵性能进行了评估，这两种原料因其抑制剂浓度高而被选用。Fm17的表现优于工业菌株乙醇红，分别从刺芹和芦苇中生产出高达18克/升和39克/升的乙醇，乙醇产量始终高于基准菌株。这种天然菌株在木质纤维素乙醇工厂中作为优质酵母具有巨大的应用潜力。
