Modulation of Fatty Acid Composition of Aspergillus oryzae in Response to Ethanol Stress

Abstract

The koji mold Aspergillus oryzae 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 A. oryzae, and there is a decline in hydrolysis efficiency. However, the protective mechanisms of A. oryzae 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 A. oryzae, 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 A. oryzae 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 A. oryzae and offer target genes for ethanol tolerance enhancement via genetic engineering.

Ethanol Inhibits Aflatoxin B1 Biosynthesis in Aspergillus flavus by Up-Regulating Oxidative Stress-Related Genes

“…As a general cell toxic substance, ethanol affects the integrity of the cell membrane, inactivates cellular enzymes, and destroys protein structure, leading to the inhibition of fungal growth, viability, and conidia formation (Ma et al, 2019). In addition, ethanol triggered internal cellular perturbations like irregular nuclei and the aggregation of scattered vacuoles in fungal cells.…”

“…Ma et al (2019) indicated that ethanol stress induced an obvious suppression of Aspergillus oryzae growth and conidia formation, and the inhibitory effect increased with ethanol concentration. As a general cell toxic substance, ethanol disturbed many cellular processes, such as irregular nuclei, the aggregation of scattered vacuoles, the increase of unsaturated fatty acid, and the overexpression of related fatty acid desaturases (Ma et al, 2019).…”

“…As we all know, ethanol is an inhibitor of the growth of bacteria and fungi (Ma et al, 2019). Previous studies showed that the accumulation of ethanol inhibited yeast cell growth and viability, affected the integrity of the cell membrane, and inactivated cellular enzymes, resulting in cell death during fermentation (Gibson et al, 2007;Kim et al, 2016;Ma et al, 2019). Ma et al (2019) indicated that ethanol stress induced an obvious suppression of Aspergillus oryzae growth and conidia formation, and the inhibitory effect increased with ethanol concentration.…”

“…Previous studies showed that the accumulation of ethanol inhibited yeast cell growth and viability, affected the integrity of the cell membrane, and inactivated cellular enzymes, resulting in cell death during fermentation (Gibson et al, 2007;Kim et al, 2016;Ma et al, 2019). Ma et al (2019) indicated that ethanol stress induced an obvious suppression of Aspergillus oryzae growth and conidia formation, and the inhibitory effect increased with ethanol concentration. As a general cell toxic substance, ethanol disturbed many cellular processes, such as irregular nuclei, the aggregation of scattered vacuoles, the increase of unsaturated fatty acid, and the overexpression of related fatty acid desaturases (Ma et al, 2019).…”

Effects on Gene Transcription Profile and Fatty Acid Composition by Genetic Modification of Mevalonate Diphosphate Decarboxylase MVD/Erg19 in Aspergillus Oryzae

“…Total lipids extraction was performed according to a previously described method [32,33]. Briefly, 48-h-old A. oryzae mycelia were collected and vacuum freeze-dried to a constant weight.…”