Research On Lycopene High-Producting Strains Breeding And Fermentation Optimization

As one of natural carotenoids,lycopene has many physiological health functions on human body. Therefore, the research of lycopene is a hot topic in the field of food, health care products, cosmetics, etc in the world.The method of lycopene fermentation has the advantage of low cost, short production cycle, safe and non-toxic, so it is received much attention. In this work,which focus on enhancing of lycopene production,the high productivity strain was selected and bred for lycopene production was optimized.The main research contents and results are as follows:Blakeslea trispora Y (+) and Y (-) were used as the starting strains. After treated with NTG, UV and LiCl complex mutagenesis processing,mutant strains Y(+)-63and Y(-)-43with high lycopene productivity were screened out by using the flat plate preliminary screening and the shake flask secondary screening.Under the fermentation condition without being optimized,the production of lycopene was0.46g/L,which was27.8%higher than the parental strains Y (+) and Y (-).The strains are genetically stable.The effect of lycopene synthesis with the ways and conditions of fermentation were investigated.The method of Blakeslea trispora strains (+) and (-) in a ratio of1:5directly inoculation in fermentation medium was indetermined,which was as follows:inoculation size103spores/mL fermentation liquid,temperature27℃,medium load amount50mL/500mL shaking flask, rotary speeds of shaking flask220rpm,1%n-Dodecane and0.15%Tween80added at0h,0.471mmol/L β-ionone added at36h,30mg/L ketoconazole and1g/L imidazole added at50h,culture time6days.The media components of mated Blakeslea trispora producing lycopene were optimized using response surface design.The optimum media components were:36.6g/L of Glucose,26.9g/L of Corn steep liquor,1.2g/L of K2HPO4,40g/L of Modified starch,40g/L of Soybean cake powder,40g/L of Oil,0.1g/L of MgSO4,0.01g/L of VB1,pH6.7.After being verified, the model is high significance. The optimized medium formulation is compared with the original fermentation medium and single factor optimized medium, lycopene production increased by42%and23%, respectively.According to stirring speed on the impact of lycopene fermentation process, the controlling fermentation process parameters of15L bioreactor is determined:culture temperature27℃, the air flow0.5m3/h, stirring speed starting at200rpm, when the level of dissolved oxygen from the initial100%down to30%, stirring speed is gradually increased up to600rpm at the post-fermentation. Under this condition,lycopene production was1.14g/L at the end of fermentation,which was16%higher than that of shaking-flask fermentation.Based on the analysis of batch fermentation process and intermittent and constant carbohydrate supplement,an improved pH-control carbohydrate supplement strategy for Blakeslea trispora producing lycopene. Having considered the pH variation and the glucose consumption status,The proposed carbohydrate supplement policies effectively avoid underfeeding or overfeeding, lycopene production reached1.43g/L,which increased by25.4%compared to that of batch fermentation (1.14g/L).