| 【Objective】Isolate and identify Saccharomyces cerevisiae strains with high enrichment rate of iron,and optimize the composition of their medium and fermentation conditions.【Method】Iron-tolerant Saccharomyces cerevisiae were isolated and bred from the rhizosphere soil of orchards,and identified by morphological,physiological and biochemical analysis and 26 S rDNA gene sequence analysis;Single factor test was used to set different types of carbon sources (glucose,sucrose,lactose,fructose,maltose)and nitrogen sources (ammonium sulfate,yeast extract,peptone,urea)，and different mass concentrations of Fe2+（100,200,300,…,1 000,1 200,1 600,2 000 μg/mL）,carbon sources(10,20,30,40,50,60,70,80,90 g/L)，nitrogen sources(inorganic nitrogen 2,4,6,8,10,20 g/L;organic nitrogen 4,8,12,16,20,24,28 g/L)，inorganic salts (MgSO4·7H2O 0.3,0.5,1.0,1.5,2.0 g/L;KH2PO4 0.5,1.5,2.5,3.5,4.5 g/L)，and to explore the effects of different medium components on the ironrich ability of Saccharomyces cerevisiae.Single factor test was used to study temperature(26,28,30,32,34,36,38 ℃),and initial pH value(3.5,4.0,4.5,5.0,5.5,6.0,6.5,7.0,7.5),inoculation amount(2%,4%,6%,8%,10%,12%),speed (140,160,180,200,220 r/min),liquid loading (20,30,40,50,60,70 mL in 250 mL triangle bottle)on the iron rich capacity of Saccharomyces cerevisiae.The L9(34) orthogonal experiment design was carried out by selecting temperature,initial pH value,inoculation amount and rotational speed to obtain the best fermentation culture conditions,and the verification experiment was carried out.【Result】An iron-tolerant saccharomyces Cerevisiae strain ZY-JM16 was isolated and identified from the soil of Sanyemutong Orchard.Through single factor test,the optimal medium composition was obtained as follows:sucrose 50 g/L，urea 4 g/L，yeast extract 24 g/L，KH2PO4 2.5 g/L，MgSO4·7H2O 0.5 g/L，Fe2+ 900 μg/mL(FeSO4·7H2O 4.5 g/L).Single factor test and orthogonal test were used to optimize,and the optimum fermentation parameters for high iron content of the strain were as follows:initial pH 4.8,temperature 28 ℃,rotation speed 180 r/min,inoculum size 6%,liquid loading size 50 mL per 250 mL,fermentation time 40 h.Under these conditions,the iron-rich rate of the strain reached 91.80%,which was 229.27% higher than that before optimization;The microbial biomass reached 13.06 g/L,which was 59.07% higher than that before optimization.【Conclusion】A strain of highly efficient iron-rich Saccharomyces cerevisiae ZY-JM16 was obtained and its culture conditions were optimized,to clarify the growth rule of the strain. |
