| Phaffia rhodozyma was chosen as the producer of astaxanthin. Theeffect of mutagenesis, optimization of the medium and additives onastaxanthin yield was studied.Atmospheric and Room Temperature Plasma (ARTP) is a newmutagenesis method, which has the advantage of simple and safeoperation and no pollution to the environment. At present, there are notrelatively reports about Phaffia rhodozyma with ARTP. An astaxanthinhyper-producing mutant A7was obtained by ARTP method of originalstrain AS2.1557and3×10-4beta-ionone screening. A7strain has geneticstability through continuous passage culture. Astaxanthin production andastaxanthin content of mutant A7are reached1.67mg/L and224.6μg/gby YM medium, which increased40%and42%compared with those ofAS2.1557.Effects of different carbon sources, nitiogen sources, growth factorson astaxanthin biosynthesis by mutant A7were studied through the singlefactor experiment. We chose three significant factors and these factorsand their interaction were studied by response surface methodology (RSM). A optimized medium was obtained, which was composed of36.64g/L sucrose,3.1g/L (NH4)2SO4,1.79g/L yeast extract,0.1g/LCaCl2,2g/L KH2PO4,0.5g/L MgSO4and0.1g/L NaCl2. The effect ofinoculum size, agitation speeds, temperature, liquid volume and initial pHvalue on the astaxanthin production by X. dendrorhous was studied. Theoptimum conditions were10%,200rpm,20°C,50ml and5.5,respectively. In this medium, the biomass of Phaffia rhodozyma,astaxanthin yield were8g/L and3.6mg/L. In addition, we also studiedthe growth of mutant strains in the fermentation tank and drew a varietyof kinetic curves of the Phaffia rhodozyma. We could continue to do theresearch of the subsequent kinetics and fermenter culture in furtute.We studied the influence of additives on the growth and astaxanthinproduction by original strains, firstly. When20mg/L nicotinamide wasadded, astaxanthin production was1.8mg/L. A15%was observdcompared with the control and the addition of9mg/L nicotinic acid onlyslightly improved astaxanthin production. The effect of oxygen carrier onthe astaxanthin production was studied. Among them, the stimulation ofH2O2and soya bean oil was remarkable. When20μL/L H2O2was added,astaxanthin production was2.47mg/L. A15%was observd comparedwith the control. The addition of10ml/L soya bean oil improved37.6%.Among unsaturated fatty acids, only linolenic acid improved13%astaxanthin production, the others almost had no positive effect. We also studied the influence of additives on the growth and astaxanthinproduction by A7strains. When50.9mg/L Isoamyl enolate was added,astaxanthin production was4.07mg/L inereased10%than the control.The astaxanthin production was4.4mg/L improved40%with theaddition of1mg/L indole-3-acetic acid. |
