Abstract
Aspergillus oryzae, commonly known as koji mold, has been widely used for the large-scale production of food products (sake, makgeolli, and soy sauce) and can accumulate a high level of lipids. In the present study, we showed the dynamic changes in A. oryzae mycelium growth and conidia formation under nitrogen and phosphorus nutrient stress. The fatty acid profile of A. oryzae was determined and the content of unsaturated fatty acid was found increased under nitrogen and phosphorus limitation. Oleic acid (C18:1), linoleic acid (C18:2), and γ-linolenic acid (C18:3) production were increased on five nitrogen and phosphorus limitation media, especially on nitrogen deep limitation and phosphorus limitation group, showing a 1. 2–, 1. 6–, and 2.4-fold increment, respectively, compared with the control. Transcriptomic analysis showed the expression profile of genes related to nitrogen metabolism, citrate cycle, and linoleic acid synthesis, resulting in the accumulation of unsaturated fatty acid. qRT-PCR results further confirmed the reliability and availability of the differentially expressed genes obtained from the transcriptome analysis. Our study provides a global transcriptome characterization of the nitrogen and phosphorus nutrient stress adaptation process in A. oryzae. It also revealed that the molecular mechanisms of A. oryzae respond to nitrogen and phosphorus stress. Our finding facilitates the construction of industrial strains with a nutrient-limited tolerance.
Highlights
Fatty acids (FAs) are carboxylic acids with long aliphatic chains, which may be straight or branched, saturated or unsaturated, and the majority of FAs generally found in nature have 6–18 carbon atoms (Mohan et al, 2015)
The density of spore decline on N, N-, N- P, and N deep limitation and P sufficiency (N- -)P- media sequentially indicated that the effect of inhibition increased with nitrogen and phosphorus limitation on these media
The pathway and related biosynthesis mechanisms of FA have been well documented, the dependency of this generally regarded as safe (GRAS) strain activity on nutrient availability in a medium is only partially understood
Summary
Fatty acids (FAs) are carboxylic acids with long aliphatic chains, which may be straight or branched, saturated or unsaturated, and the majority of FAs generally found in nature have 6–18 carbon atoms (Mohan et al, 2015). FAs are comprised of saturated fatty acids (SFAs) and unsaturated fatty acids (UFAs). UFAs are typically biosynthesized by desaturation and are vulnerable to oxidation caused by hydration (water), oxidation (oxygen), metallic atoms, or microbes. UFAs can be divided into monounsaturated fatty acids and polyunsaturated fatty acids based on the number of carbon–carbon double bonds (Grama et al, 2014). UFAs are a component of the phospholipids in cell membranes and contribute to maintaining membrane fluidity. It is a fundamental component in human and animal nutrition and with the function of blood lipid
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