Preparation Of Odd-Carbon Fatty Acids By Fermentation And Its Metabolic Pathway In Rhodococcus Opacus PD630

Odd-carbon fatty acids(OCFA)have essential functional characteristics and are widely used in food and pharmaceutical industries,as well as the chemical industry.Rhodococcus opacus PD630(R.opacus PD630)can use various organic compounds as its carbon source,has a high oil accumulation capacity and can synthesize a higher proportion of OCFA under natural conditions.In this study,the content of OCFA was significantly increased by adding 1-propanol to the fermentation medium of R.opacus PD630.And a high-yield OCFA process was obtained.Furthermore,the characteristic of OCFA oil from R.opacus PD630 was examined in detail.Then the metabolic pathway,which promoted the significant accumulation of OCFA,was revealed.The detailed research contents and results are as follows:(1)Preparation of OCFA oil by fermentation.R.opacus PD630 was used to prepare OCFA oil by fermentation.It was found that the addition of 1-propanol significantly increased the content of OCFA,and a high-yield OCFA process was established.When 1%(v/v)1-propanol in combination with glucose was used as the fermentation carbon source,the proportion of OCFA in total fatty acids increased from 29.45% to 84.51%,an increase of 186.96%.(2)Composition and thermal properties of OCFA oil.In this study,OCFA oil was prepared and extracted by R.opacus PD630 using 1-propanol combined with glucose as the carbon source through a 100 L fermentation tank and subcritical extraction technology.Gas chromatography,ultra-performance liquid chromatography-mass spectrometry,and differential scanning calorimetry were used to analyze the fatty acids composition and positional distribution,triacylglycerol(TAG)molecular species,and thermal properties of OCFA oil,respectively.It was discovered that the proportion of OCFA in total fatty acids reached to 68.15%.Saturated fatty acids such as palmitic acid(C16: 0)were preferentially located at sn-2 position in TAG.The most abundant TAG included He Pa Ha,He PHa,He Pa He,He Ha Ha,He Pa O,and He PPa.It was confirmed that the 1,3-random-2-random theory was applicable to R.opacus PD630.As to thermal profiles,it was found that the oil had a low melting point and recrystallization was detected.(3)Study on the metabolic pathway of high-yield OCFA in R.opacus PD630.Based on metabolomics and transcriptomics,differential metabolites and transcripts of R.opacus PD630 with or without 1-propanol were comprehensively analyzed.The metabolic pathway contributing to the significant improvement of the OCFA content in R.opacus PD630 with 1-propanol was revealed.In the presence of 1-propanol,the amount of propionyl-Co A synthesis increased significantly,and the expression of 1-propanol metabolic pathway and methylmalonyl-Co A pathway in the cells increased,resulting in increased OCFA synthesis.Also,the stress mechanism in the presence of 1-propanol was elucidated.Cells became shorter and thicker.It is also manifested in the reduction of short peptides,the increase of unsaturation degree in cell membrane phospholipids.And OCFA synthesis pathway was strengthened to increase the content of OCFA.In this paper,the high-yield process conditions of OCFA oil were obtained through carbon source optimization.The composition and thermal properties of OCFA oil were analyzed,and the metabolic pathways that 1-propanol can promote large amounts of OCFA synthesis were clarified.It provides a new strategy for the preparation of OCFA by microbial method,and provides a basis for the regulation of R.opacus PD630 fermentation carbon source and OCFA accumulation.