Breeding Of B.trispora By Pulsed Magnetic Field Mutagenesis And Studying The High-yield Characteristics Of ?-carotene Production

?-carotene is one of the most nutritious natural pigments,and has strong antioxidant activity.The production of?-carotene by microbial fermentation methods such as B.trispora is one of the most promising methods,but its production cannot meet the industrial production needs.In this paper,the strains of B.trispora were selected by pulsed magnetic field technology to obtain?-carotene high-yield strains.The characteristics of the high yield strain and the original strain were compared and analyzed.The main findings obtained are as follows:?1?High-yield strains of B.trispora?-carotene were obtained by mutagenesis using pulsed magnetic field technique.When the number of pulses is 9 and the magnetic field strength is 7 T,the mutagenic effect is the best.The highest yield of?-carotene in the mutagenized strain can reach 1.41±0.05 g/L,which is 60%higher than that of the original strain.?2?The obvious characteristics of the high-yielding strains were analyzed in comparison with the starting strains.Compared with the original strain,the obtained high-yield strain has the characteristics of higher glucose utilization rate,higher accumulation of?-carotene,coarser mycelium and lesser aggregation.Meanwhile,it is found that the extracellular lipase activity of the high-yield strain is more stable.The activity of extracellular lipase is high,and the activity to utilize exogenous oils is improved,and the enzymes activity and genes expression of the key enzymes of antioxidant stress?SOD and CAT?which are closely related to the synthesis of?-carotene,which were significantly increased compared with the original strain.Further studies showed that the expression level of INO₄ gene,a transcription factor regulating phospholipid biosynthesis,was decreased in high-yield strains,indicating that the phospholipid biosynthesis pathway of high-yield strains was weakened,which was conducive to the metabolic flow to?-carotene.?3?The effect of oil on the synthesis of?-carotene in high yield strains was studied.It was found that 30 g/L soybean oil was most conducive to the synthesis of?-carotene from high-yielding strains.The analysis of several oil components showed that the linoleic acid content in oil was positively correlated with the yield of?-carotene.Further studies confirmed that the yield of?-carotene from high-yielding strains increased by 118%compared with that without linoleic acid at the initial stage of fermentation.The results showed that a certain concentration of linoleic acid can promote the synthesis of?-carotene in high-yield strains.The results provided experimental basis for further improving the yield of?-carotene.