Research On Effects Of Low-Frequency Alternating Magnetic Field On Liquid Fermentation Of Antrodia Camphorata And Its Mechanisms

As an edible and medicinal fungus,Antrodia camphorata has high nutritional and commercial values.The liquid fermentation is usually used to obtain mycelia with various active substances.Currently,magnetic field has been used to promote microbial growth or microbial metabolites synthesis,and the effect is remarkable.In this study,the low-frequency alternating magnetic field and the RNA-Seq technique were applied into liquid fermentation of Antrodia camphorata to improve mycelial biomass and explore the mechanism of magnetic field on liquid fermentation,respectively.The main results were as follows:(1)Study on effects of low-frequency alternating magnetic field on liquid fermentation of Antrodia camphorata and its scale-up experiment: The purpose of this part is to improve the liquid fermentation using low-frequency alternating magnetic field.For this reason,using mycelial biomass promotion rate of Antrodia camphorata as the evaluation index,the effects of low-frequency alternating magnetic field on liquid fermentation of Antrodia camphorata were studied.The results showed that when the intensity of magnetic field was 80 Gs,magnetic treatment start time was 3 d after inoculation and duration time was 4 h,the magnetic field had a strong stimulation on the Antrodia camphorata liquid fermentation.Under these conditions,the biomass of Antrodia camphorata,the yield of triterpenoid and polysaccharide increased by 15.87%,26.85% and 24.26%,respectively.Under the optimal conditions,the scale-up experiment was carried out in a 5 L fermenter.The results showed that the biomass of Antrodia camphorata,the yield of triterpenoid and polysaccharide increased by 10.61%,29.91% and 20.81%,respectively.And using the 5 L fermenter could make the fermentation finish 27 h ahead of normal time.It can be concluded that the magnetic field-assisted fermentation can increase the mycelial biomass,polysaccharide and triterpenoid yield of Antrodia camphorata,and shorten fermentation time.(2)The effects of low-frequency alternating magnetic field on the mycelium structure of Antrodia camphorata: The purpose of this part is to explore the effects of low-frequency alternating magnetic field on mycelium at the cellular level.For this reason,the changes of mycelium structure were observed by scanning electron microscopy and transmission electron microscopy.After magnetic field treatment,the mycelium morphology was rougher and looser,the cell walls were slightly thinner,and the vacuole and mitochondria volume were larger than that of untreated mycelium,indicating that magnetic field treatment affected the structure of cells.The fluorescence polarization technique was used to determine the membrane fluidity with the fluorescence probe DPH.The results showed that the fluorescence polarization and fluorescence anisotropy decreased with the increase of magnetic induction time.The increased of membrane fluidity promoted the exchange rate of intracellular and extracellular substances.This may be one of the reasons for the increase of mycelial biomass.(3)The effects of low-frequency alternating magnetic field on gene expression of Antrodia camphorata: The purpose of this part is to explore the mechanism of low-frequency alternating magnetic field promoting liquid fermentation of Antrodia camphorata at the molecular level.21431 Unigene were obtained from mycelia of Antrodia camphorata by the transcriptome sequencing technique.1880 differential genes including 1873 up-regulated genes and 7 down-regulated genes were obtained through the experimental group vs the control group by differentially screening.The GO enrichment analysis showed that the differential genes were mostly enriched in the metabolic process and catalytic activity.The KEGG enrichment analysis showed that the differential genes were almost enriched in arginine and proline metabolism,ubiquitin mediated proteolysis,beta-alanine metabolism,cysteine and methionine metabolism,valine,leucine and isoleucine degradation,and citrate cycle.Additionally,it was found that high-expressed genes related to amino acid metabolism,signal transduction,citrate cycle and endocytosis contributed to the increase of mycelial biomass,polysaccharide and triterpenoid yield of Antrodia camphorata.