Microbial oils are regarded as promising alternatives to fossil fuels. For bio-oil production to be sustainable over the long term, utilizing low-cost substrates like volatile fatty acids (VFAs) is crucial. Increasing attention is being paid to one of the most common VFAs: propionate, a substrate that could be used to produce the odd-chain FAs of industrial interest. However, little is known about microbial responses to propionate-induced stress and the genes involved. Using genomic library screening, we identified two genes involved in propionate tolerance in Yarrowia lipolytica-MFS1 and RTS1. Strains containing each of the genes displayed enhanced tolerance to propionate even when the genes were expressed in truncated form via a replicative plasmid. Compared with the control strain, the strain overexpressing MFS1 under a constitutive promoter displayed greater tolerance to propionate: It had a shorter lag phase and higher growth rate in propionate medium (0.047 hr-1 versus 0.030 hr-1 for the control in 40 g/L propionate); it also accumulated more total lipids and more odd-chain lipids (10% and 3.3%, respectively) than the control. The strain overexpressing RTS1 showed less tolerance for propionate than the strains harboring the truncated form (0.057 hr-1 versus 0.065 hr-1 in 40 g/L propionate medium) but still had higher tolerance than the control strain. Furthermore, the overexpression of RTS1 seemed to confer tolerance to other weak acids such as lactate, formic acid, malic acid, and succinic acid. This work provides a basis for better understanding the response to propionate-induced stress in Y. lipolytica.

中文翻译：

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在基因组文库中筛选解脂耶氏酵母中丙酸耐受性相关基因。

微生物油被认为是化石燃料的有前途的替代品。对于长期可持续的生物油生产，利用低成本基质（如挥发性脂肪酸（VFA））至关重要。人们越来越关注最常见的VFA之一：丙酸酯，一种可用于生产具有工业价值的奇链FA的基质。但是，人们对微生物对丙酸诱导的应激反应和涉及的基因知之甚少。使用基因组文库筛选，我们确定了解脂耶氏酵母-MFS1和RTS1中的丙酸耐受性的两个基因。包含每个基因的菌株对丙酸的耐受性增强，即使这些基因通过复制质粒以截短的形式表达时也是如此。与对照菌株相比，在组成型启动子下过表达MFS1的菌株显示出对丙酸酯的更大耐受性：它在丙酸酯培养基中具有更短的滞后阶段和更高的生长速率（在40 g / L丙酸酯中，对照组为0.047 hr-1比0.030 hr-1）；与对照相比，它还积累了更多的总脂质和更多的奇链脂质（分别为10％和3.3％）。过表达RTS1的菌株对丙酸的耐受性低于带有截短形式的菌株（在40 g / L丙酸酯培养基中为0.057 hr-1对0.065 hr-1），但仍比对照菌株具有更高的耐受性。此外，RTS1的过表达似乎赋予了对其他弱酸的耐受性，例如乳酸，甲酸，苹果酸和琥珀酸。这项工作为更好地了解解脂耶氏酵母中丙酸诱导的应激反应提供了基础。