Studies On Fermenting Process And Metabolic Regulation For Producing β-carotene By Blakeslea Trispora

β-carotene is the precursor of vitamin A and it is an important natural pigments.β-carotene has predominantly function of antioxidant, anti-aging, inhibition ofcardiovascular disease, anticancer, prevent and treat cataract. It is also used in foodcolorants and calciumoxide. In addition it is used as an margarine, capsule, costmetic eg.In this paper, Blakeslea trispora was mutated to obtain high production β-carotene strain.The fermentation conditions and medium were optimized, the aim was to improve thecapacity of these strains to produce β-carotene. There were the detailed researchingcontents.1) The culture medium and cultivating condition of original strain were optimized.First, seed cultivation condition of original strain was optimized, the result showed thatthe best seed culture medium was listed as follow: corn flour3%, soybean flour3%,KH2PO40.1%, MgSO40.02%, VB10.001%. The seed culture conditions of original trainwas obtained as following: temperature28℃, rotating speed200rpm, original pH6.5,seed age of strain (+)20h and strain (-)25h. At the basis of the optimization of seedcultivation, optimization medium composition for original strain was selected asfollowing: glucose7.16%, soybean flour1%, Wheat bran extract4.08%, KH2PO40.2%,MgSO40.04%, VB10.01%, soybean oil3%. The maximal β-carotene production oforiginal strain was645mg/L, which agreed with the predicted values well. Theoptimization fermentation conditions of original train was obtained as following:fermentation time144h, inoculum size9%, the ratio of strain (+) to strain(-)1:5,original pH6, culture temperature28℃, rotating speed180rpm.2) The mutation breeding of the the original negative strain of Blakeslea trisporawas carried out by ultraviolet radiation (UV) and compound mutagenesis (UV and LiCl).First, it was mutated by ultraviolet radiation (UV). The best mutated time was10minand mutation strain UV-Ⅱwas obtained. Then the strain UV-Ⅱwas mutated bycompound mutagenesis (UV and LiCl) and mutation strain L-5was obtained. Theβ-carotene production of mutation strain L-5was1126mg/L. By genetic stability tested,strain L-5showed a good stability.3) The culture medium and cultivating condition of mutant strain L-5wereoptimized. The optimization culture conditions were obtained as following: seed age ofstrain (+)20h and strain (-)25h, fermentation time168h, inoculum size9%, the ratioof strain (+) to strain (-)1:9, original pH6.5, culture temperature28℃, rotating speed200rpm. Then based on the optimization culture conditions, optimization mediumcomposition was selected as following: glucose9%, soybean flour0.3%, Wheat branextract4%, KH2PO40.2%, MgSO40.05%, VB10.001%, soybean oil1%. Under theidentified optimal conditions, the maximal β-carotene production was1298mg/L.4) The regulating additives were added into the optimal fermenting medium to study the effect on β-carotene production. The effective conditions were obtained asfollowing:30mg/L ketoconazole was added into the medium after30h olderinoculation,0.1%β-ionone was added into the medium after36h older inoculation,0.1%Span-20and1%dodecane were added into the medium, these conditionseffectively improved β-carotene production. At last, optimal agitation speed andaeration rate in15L stirred tank reactor on the basis of the optimization of cultivationwere100rpm and1.5vvm, respectively.