Screening Of β-carotene Producing Strain,Optimization Of Fermentation Process And Application In Juice And Carbonated Beverages

Recently,the natural pigment market is more and more concerned about biological functions and food safety issues.Chemically synthesizedβ-carotene is generally less expensive than natural pigment,but many uncertain diseases are associated with the use of synthetic pigment.Theβ-carotene extracted from plants is restricted by the raw materials,climate,and transportation conditions.Therefore,research on the production ofβ-carotene by microbial fermentation is particularly important.In this study,high-yieldβ-carotene strains were screened from samples such as soil,and it’s yield was optimized from liquid fermentation and solid-state fermentation,and the stability of juice and carbonated beverages were studied.1.There were 70 colored strains isolated from soil and rot,22 of them were able to produceβ-carotene,including 19 yeast strains and 3 bacteria strains.Four strains were selected for ITS sequence analysis,and similarity sequences were compared with known sequences in the GenBank database by Blast tools.Finally,S3-1 and S3-6 were identified as Sporidiobolus pararoseus,S17-1 and S33-2 were Rhodotorula sp.respectively.2.The composition and fermentation conditions of Sporidiobolus pararoseus S3-1medium were optimized by single factor and orthogonal experiment.The optimum medium composition were:glucose 40 g/L,yeast extract 30 g/L,MgSO₄ 0.2 g/L,anhydrous CaCl₂0.5 g/L,KH₂PO₄ 0.8 g/L;The optimum fermentation conditions were:initial volume40 mL/250 mL,initial pH 5.0,inoculation 6.0%,incubation for 84h.Under the optimized conditions,the biomass reach to 21.03 g/L,and theβ-carotene yield reach to（3.08±0.46）mg/L,which was 76%and 43%higher than that before respectively,and the purity was 60%.3.The solid-state fermentation process of sporidiobolus pararoseus S3-1 was optimized.The soybean meal and the beer gains were used as the main fermentation substrate.The peptone was the best nitrogen by single factor.The optimized conditions were as follows:soybean meal:beer gains=7:3.inventory 22.80 g/250 mL,peptone 0.5 g/L（0.61 g/kg substrate）,inoculation13%,water content 55%,temperature 30°C,pH 5.0,incubation for 84 h。Under optimal fermentation conditions,the yield ofβ-carotene reach to 2.71 g/kg dry basis,which was 70%higher than that before.The content of crude protein in the mixed matrix after fermentation increased by 5%,the crude fat content decreased by 68%.The total amount of amino acids was20%higher than that before.Among them,histidine,leucine,methionine,serine and isoleucine had a large increase.It is more suitable for animal feed.4.The light stability ofβ-carotene produced by Sporidiobolus pararoseus S3-1 was compared with synthetic pigment.The results show that stored in outdoor natural light for 12days,β-carotene was more suitable for juice than carbonated beverages;In carbonated beverages,syntheticβ-carotene was more stable than fermented.The fermentedβ-carotene had better stability than the synthetic type within 12 days of storage under indoor lighting,and the preservation rate was above 90%.The thermal stability of fermentedβ-carotene was compared with synthetic.The results showed that the storage rate was above 89%after storage at20°C⁶0°C for 6 h.Both had relatively high thermal stability within 6 h.