Modulation of Fatty Acid Composition of <i>Aspergillus oryzae</i> in Response to Ethanol Stress

The koji mold <i>Aspergillus oryzae</i> is widely adopted for producing rice wine, wherein koji mold saccharifies rice starch and sake yeast ferments glucose to ethanol. During rice wine brewing, the accumulating ethanol becomes a major source of stress for <i>A. oryzae</i>,...

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Bibliographic Details
Main Authors: Long Ma, Lijun Fu, Zhihong Hu, Yongkai Li, Xing Zheng, Zhe Zhang, Chunmiao Jiang, Bin Zeng
Format: Article
Language:English
Published: MDPI AG 2019-06-01
Series:Microorganisms
Subjects:
Online Access:https://www.mdpi.com/2076-2607/7/6/158
Description
Summary:The koji mold <i>Aspergillus oryzae</i> is widely adopted for producing rice wine, wherein koji mold saccharifies rice starch and sake yeast ferments glucose to ethanol. During rice wine brewing, the accumulating ethanol becomes a major source of stress for <i>A. oryzae</i>, and there is a decline in hydrolysis efficiency. However, the protective mechanisms of <i>A. oryzae</i> against ethanol stress are poorly understood. In the present study, we demonstrate that ethanol adversity caused a significant inhibition of mycelium growth and conidia formation in <i>A. oryzae</i>, and this suppressive effect increased with ethanol concentration. Transmission electron microscopy analysis revealed that ethanol uptake triggered internal cellular perturbations, such as irregular nuclei and the aggregation of scattered vacuoles in <i>A. oryzae</i> cells. Metabolic analysis uncovered an increase in fatty acid unsaturation under high ethanol conditions, in which a large proportion of stearic acid was converted into linoleic acid, and the expression of related fatty acid desaturases was activated. Our results therefore improve the understanding of ethanol adaptation mechanisms in <i>A. oryzae</i> and offer target genes for ethanol tolerance enhancement via genetic engineering.
ISSN:2076-2607