Effect Of Dissolved Oxygen And Stirring On The Echinocandin B Fermentation

Echinocandin B?ECB?is a novel cyclo-lipopeptide antibiotics produced by Aspergillus nidulan,which is the precursor for the synthesis of antifungal drug anidulafungin.In this work,the Aspergillus nidulans ZJB09223 strain was selected for ECB production mutagenized by our lab.The ECB Fermentation conditions were optimized,and the effect of dissolved oxygen and stirring on ECB fermentation was studied.The major reserch results are as follows:The culture conditions for improving ECB fermentation production were optimized,and the optimized conditions were as follows:seed age44-48h,inoculum size 12%?v/v?,and initial pH 6.8.The optimum carbon source is methyl oleate,and the optimal concentration was 80g/L.ECB production reached to 2354 mg/L,51.8%higher than that of the fermentation of mannitol as carbon source.The effect of oxygen carrier on the ECB production was conducted at hypoxic conditions with 100mL medium in 250 mL shaking flask.The results indicated that 1.5%of n-hexane as an oxygen carrier may make the ECB production increased by 41.8%;at the same time when 1.5%n-hexane as the oxygen carrier and 0.5%span-20 as a surfactant were added to the fermentation medium,ECB production reached to 897 mg/L,61.2%higher than that of the hypoxic conditions.Then the effect of dissolved oxygen on the ECB production was studied in 30 L fermenter,the results indicated that with the increasing aeration rate,the dissolved oxygen level was improved at the initial fermentation period,but then the dissolved oxygen also keep at a very low level.The ECB fermentation production was 704.5 mg/L at 1 vvm,30.7%higher than that of the0.5vvm.The lower dissolved oxygen could not be improved by increasing the aeration;therefore,the following experiments were controlled by oxygen.The ECB production could reach to 1118.3 mg/L at30-40%dissolved oxygen level,which suggested that DO have great effect on the fermentation production of the ECB.Aspergillus nidulans ZJB09223 was sensitive to shear force.The ECB production in flat baffled flask and tip baffled flask were1279.6mg/L and 1398.4 mg/L,which were decreased by 22.6%and11.9%,respectively,and the fermentation period was shorted.Micro-particles can influence cell morphology and ECB production,the effect of two kinds of micro-particles of talcum powder and glass beads on ECB production was investigated.The results showed that the 20 g/L of talcum powder(d₅₀=14.2?m)and seven glass beads?d=6 mm?made the ECB fermentation production reached to 1262.9 mg/L and1344.1mg/L,which has increased 33.2%and 41.7%,respectively,compared with the control.At last,the effect of different impeller types on the ECB production was studied in 30 L fermenter,the results showed that ECB production reached to 1208 mg/L with parabolic disc turbine impeller,which increased 71.3%compared with the control.