Screening Of High-yield Coenzyme Q₁₀ Strain With Oxygen-limited Model And The Study On Optimization Of The Fermentation Process

Coenzyme Q10 is a natural antioxidant and metabolic activator,which has attracted more and more attention due to its excellent health-care effect.In order to improve the yield of industrial production and expand the market,the high-yield Coenzyme Q10 producing strain and optimization of the fermentation process were studied.Firstly,the high-throughput culturing system for Rhodobacter sphaeroides was established.The strain was treated for 25 seconds by the atmospheric and room temperature plasma(ARTP)to obtain the positive mutants,in which the fatality rate was 86.02%.An oxygen-limited model based on the characteristics of Coenzyme Q10 was designed by adding 0.4 g/L sodium sulfite to the culturing plates.A mutant R.sphaeroides F5D13,which could survive in oxygen-limited environment and performed high-yield production of Coenzyme Q10,was screened out.This strain showed a strong demand of oxygen affinity in 5L fermentation reactor,while the titer was increased by 18%compared to the original strain.Secondly,a single factor experiment was carried out on the initial fermentation medium to investigate the effect when one nutrient was absent.Then the significant factors potassium dihydrogen phosphate and ammonium sulfate were further studied.The initial phosphate concentration would affect the balance between the growth of bacteria and the synthesis of products.The specific titer had a marked increase by limiting the phosphate concentration.The decrease of nitrogen could cause the unbalance C/N ratio,impacting the flow of glucose and stimulating the accumulation of by-product polysaccharide.Therefore,the broth viscosity became extremely high.When the concentration of ammonium sulfate was 3 g/L,the broth viscosity and the production of Coenzyme Q10 were obviously improved.Finally,the influence of oxygen supply level on Coenzyme Q10 fermentation was investigated in 50L reactor.As a result,a new OUR-stat directed strategy with consecutive feeding ammonium sulfate was successfully established.The OUR level during the late phase was controlled at 45±2.6 mmol/L/h by adjusting the ammonium sulfate solution feeding rate at 130±12 mg/L/h.The optimized fermentation process was scaled up in 100 m3 reactors and the highest Coenzyme Q10 content was 2916±80 mg/L.