High-density Cultivation of Lycopene-producing Engineered Bacteria in 5 L Fermenter and Optimization of Fermentation Conditions
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Abstract:
In this study, the fermentation conditions of lycopene-producing engineered Bacteria W-05 were optimized. Firstly, single factor experiments were used to determine the type of culture medium, culture temperature, preferred sources of carbon and nitrogen, and inorganic salt. Then, according to the results of the single factor experiments, the response surface experiments were set up to determine the interaction between various factors. The results of the response surface experiments showed the components of the medium: peptone 10.00 g/L, yeast extract powder 5.00 g/L, glycerol 7.80 mL/L, ammonium nitrate 3.30 g/L, KH2PO4 1.80 g/L, and NaCl 11.62 g/L, under which, the lycopene yield reached a theoretical value of 3.42 mg/L. W-05 was then cultured at a high density using the optimized medium in a 5 L fermenter, and the experimental results showed the optimal fermentation conditions: pH 7.0, dissolved oxygen percentage about 20%, and the use of exponential fed-batch strategy. Under these conditions, the biomass and lycopene production of W-05 increased significantly (p<0.05), compared with those obtained via batch fermentation. The dry weight of bacterial cells reached 16.55 g/L and lycopene yield reached 19.93 mg/L after the optimized fermentation for 29 h. These results show that improving the medium composition and fermentation conditions can greatly increase the yield of lycopene produced by engineered bacterium W-05.
