Department of Biology, Lund University, Lund, Sweden.
Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana.
J Ind Microbiol Biotechnol. 2019 Feb;46(2):133-145. doi: 10.1007/s10295-018-2107-4. Epub 2018 Nov 28.
The use of thermotolerant yeast strains is an important attribute for a cost-effective high temperature biofermentation processes. However, the availability of thermotolerant yeast strains remains a major challenge. Isolation of temperature resistant strains from extreme environments or the improvements of current strains are two major strategies known to date. We hypothesised that bacteria are potential "hurdles" in the life cycle of yeasts, which could influence the evolution of extreme phenotypes, such as thermotolerance. We subjected a wild-type yeast, Lachancea thermotolerans to six species of bacteria sequentially for several generations. After coevolution, we observed that three replicate lines of yeasts grown in the presence of bacteria grew up to 37 °C whereas the controls run in parallel without bacteria could only grow poorly at 35 °C retaining the ancestral mesophilic trait. In addition to improvement of thermotolerance, our results show that the fermentative ability was also elevated, making the strains more ideal for the alcoholic fermentation process because the overall productivity and ethanol titers per unit volume of substrate consumed during the fermentation process was increased. Our unique method is attractive for the development of thermotolerant strains or to augment the available strain development approaches for high temperature industrial biofermentation.
耐热酵母菌株的使用是高性价比高温生物发酵过程的一个重要特性。然而，耐热酵母菌株的可用性仍然是一个主要挑战。目前已知的两种主要策略是从极端环境中分离耐热菌株或改进现有菌株。我们假设细菌是酵母生命周期中的潜在“障碍”，这可能影响耐热等极端表型的进化。我们将野生型酵母 Lachancea thermotolerans 依次与六种细菌共培养了几代。在共进化之后，我们观察到在有细菌存在的情况下生长的三个酵母重复系可以在 37°C 下生长，而平行运行的没有细菌的对照系只能在 35°C 下生长不良，保留了祖先的中温特性。除了耐热性的提高，我们的结果还表明发酵能力也得到了提高，使这些菌株更适合酒精发酵过程，因为在发酵过程中，单位体积消耗的基质的整体生产力和乙醇浓度都有所提高。我们独特的方法对于开发耐热菌株或增强高温工业生物发酵中可用的菌株开发方法很有吸引力。
