| PHB is synthesized by many microorganisms when carbon and nitrogen is unbalance in microorganisms as carbon sources and energy.As biological synthetic material,PHB has biological compatibility and optical activity.Coenzyme Q10(CoQ10)is used as an oral prophylaxis and therapy for cardiovascular and mitochondrial respiratory-chain diseases,among others.This study aims to isolate and optimize the culture conditions of novel bacteria with higher coenzyme Q10 production activity.Our laboratory has a bacteria Methylobacterium sp.XJLW.It can produce PHB and CoQ10 from methanol.As we know that methanol is a cheap chemical raw material,it can reduce the cost of fermentation obviously,so it has important implications.In our experiment,we investigate the effects of media component and condition of culture on bacteria biomass and production of PHB.And result shows media M3 is better than others for bacteria growth and PHB,in the conditions of initial methanol 1.5%(v/v),nitrogen sources 0.5 g/L,inoculate volume 2%(v/v),temperature 30 ? and itinial pH 7.0,obtains the highest bacteria mass at 2.4 g/L and PHB is 588 mg/L.Then we study effects of fed-batch cultivation on bacteria biomass and production of PHB and CoQ10 in a 5-L fermenter.The broth of 4 days cuture in flask was used as seed culture with an inoculate volume 10%(v/v).Dissolved oxygen feedback was selected as our fed-batch strategy.After 24 h after inoculation,when the DO decreases to 20%,methanol and ammounium hydroxide was feed.The whole fermentation process last 107 h,with a total of 830 mL methanol and 103 mL ammounium hydroxide added.The final biomass reached 46 g/L with a yield of PHB and CoQ10 reaching 6.9 g/L and 22.28 mg/L,respectively.A pair of specific primers was designed based on the key enzyme Serien Hydroxymethyl-Transferase(SHMT)of Pseudomonas putida xyz-zjut.A similar size fragment of SHMT was successfully cloned from the Methylobacterium sp.XJLW with high gene sequence identity to that of Pseudomonas putida. |
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