Zara Giacomo, Angelozzi Daniele, Belviso Simona, Bardi Laura, Goffrini Paola, Lodi Tiziana, Budroni Marilena, Mannazzu Ilaria
Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agroalimentari, Sezione di Microbiologia Generale ed Applicata, Università degli Studi di Sassari, Sassari, Italy.
FEMS Yeast Res. 2009 Mar;9(2):217-25. doi: 10.1111/j.1567-1364.2008.00472.x.
To further elucidate the biosynthesis of lipids in flor strains under fermentative conditions, the transcription levels of the lipid biosynthetic genes ACS1, ACS2, ACC1, OLE1, ERG1, ERG11, ARE1 and ARE2, as well as the lipid composition and cell viability of a flor strain were compared with that of a non-flor strain during hypoxic and aerobic fermentations in the absence of lipid nutrients. While no significant differences in transcription levels or lipid compositions were observed between the two strains when oxygen was not limiting, significant differences were seen during hypoxic fermentation. In this last condition, the flor strain, in spite of higher levels of transcription of hypoxic genes, lost the abilities to desaturate fatty acids and complete ergosterol biosynthesis, and showed a dramatic loss of viability. In contrast, the non-flor strain, which showed lower transcription levels, was able to reach a balanced lipid composition and maintained a higher cell viability. One possible explanation is that the flor strain requires a higher amount of oxygen than the non-flor strain in order to carry out the oxygen-dependent steps of lipid biosynthesis under fermentative conditions.
为了进一步阐明在发酵条件下弗洛酵母菌株中脂质的生物合成，在无氧和有氧发酵且缺乏脂质营养的情况下，比较了弗洛酵母菌株与非弗洛酵母菌株中脂质生物合成基因ACS1、ACS2、ACC1、OLE1、ERG1、ERG11、ARE1和ARE2的转录水平，以及脂质组成和细胞活力。当氧气不成为限制因素时，两菌株之间未观察到转录水平或脂质组成的显著差异，但在缺氧发酵过程中则出现了显著差异。在这种情况下，尽管弗洛酵母菌株缺氧基因转录水平较高，但它失去了使脂肪酸去饱和以及完成麦角固醇生物合成的能力，并表现出活力的急剧丧失。相比之下，转录水平较低的非弗洛酵母菌株能够达到平衡的脂质组成并保持较高的细胞活力。一种可能的解释是，在发酵条件下，弗洛酵母菌株进行脂质生物合成的需氧步骤时，比非弗洛酵母菌株需要更多的氧气。
