Abstract
BackgroundMucor circinelloides WJ11 is a high-lipid producing strain and an excellent producer of γ-linolenic acid (GLA) which is crucial for human health. We have previously identified genes that encode for AMP-activated protein kinase (AMPK) complex in M. circinelloides which is an important regulator for lipid accumulation. Comparative transcriptional analysis between the high and low lipid-producing strains of M. circinelloides showed a direct correlation in the transcriptional level of AMPK genes with lipid metabolism. Thus, the role of Snf-β, which encodes for β subunit of AMPK complex, in lipid accumulation of the WJ11 strain was evaluated in the present study.ResultsThe results showed that lipid content of cell dry weight in Snf-β knockout strain was increased by 32 % (from 19 to 25 %). However, in Snf-β overexpressing strain, lipid content of cell dry weight was decreased about 25 % (from 19 to 14.2 %) compared to the control strain. Total fatty acid analysis revealed that the expression of the Snf-β gene did not significantly affect the fatty acid composition of the strains. However, GLA content in biomass was increased from 2.5 % in control strain to 3.3 % in Snf-β knockout strain due to increased lipid accumulation and decreased to 1.83 % in Snf-β overexpressing strain. AMPK is known to inactivate acetyl-CoA carboxylase (ACC) which catalyzes the rate-limiting step in lipid synthesis. Snf-β manipulation also altered the expression level of the ACC1 gene which may indicate that Snf-β control lipid metabolism by regulating ACC1 gene.ConclusionsOur results suggested that Snf-β gene plays an important role in regulating lipid accumulation in M. circinelloides WJ11. Moreover, it will be interesting to evaluate the potential of other key subunits of AMPK related to lipid metabolism. Better insight can show us the way to manipulate these subunits effectively for upscaling the lipid production. Up to our knowledge, it is the first study to investigate the role of Snf-β in lipid accumulation in M. circinelloides.
Highlights
Microbial lipids have attracted significant research interest during the past few years owing to their benefits and potential to replace conventional sources [1, 2]
Generation of Snf‐β knockout and Snf‐β overexpressing strains of M. circinelloides by genetic engineering Based on protein sequence alignment, one gene (Scaffold00011.47) that codes for β subunit of SNF1/AMPK complex was found, and named as Snf-β [26].To determine the role of Snf-β in fatty acid accumulation, both knockout mutants and overexpressing strains of this gene were generated
A study has shown that α deletion in engineered eicosapentaenoic acid (EPA) producing Y. lipolytica strain increased the EPA production by 52 % compared to the control strain. The application of this trait is not limited to EPA production but can be applied to many other industrial settings to produce valuable lipid-derived metabolites. [34]. This is the first study to determine the role of β subunit of AMPK/SNF1 in lipid accumulation in M. circinelloides WJ11
Summary
Microbial lipids have attracted significant research interest during the past few years owing to their benefits and potential to replace conventional sources [1, 2]. Some oleaginous microbes can produce polyunsaturated fatty acids (PUFAs) that are considered essential fatty acids, they must be obtained from external sources as the human body cannot synthesize them [3,4,5]. M. circinelloides is a well-known filamentous fungus, considered to be the microbial factory for the production of useful natural compounds and metabolites [9]. They have the capability of producing a high amount of PUFAs rich in GLA (γ-linolenic acid, 18:3, delta-6,9,12) [8, 10]. Mucor circinelloides WJ11 is a high-lipid producing strain and an excellent producer of γ-linolenic acid (GLA) which is crucial for human health. The role of Snf-β, which encodes for β subunit of AMPK complex, in lipid accumulation of the WJ11 strain was evaluated in the present study
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