Optimization For Fermentation Conditions Of Phenazing-1-Carboxylic Acid In Genetically Engineered Bacteria M18Q

The Pseudomonas sp. M18, isolated from the watermelon rhizosphere in 1996, is antagonistic against a number of soil-borne pathogens and could promote plant growth. This capability is primarily due to its ability to produce several antibiotics, such as phenazine-1-carboxylic acid (PCA), pyoluteorin (Plt) and so on. QscR functions as a global repressor and qscR negatively regulates PCA production in Pseudomonas sp. M18. We constructed Pseudomonas sp. M18Q mutant strain by homologous recombination technique. In PPM medium, synthesis of PCA in M18Q was higher than that in wild-type M18.To increase the production of PCA by M18Q, we primarily screen out the proper age of seed, liquid volume (ml), inoculum (%) and compositions of the medium to be optimized. When 3% (v/v) culture with 14h age of seed (OD≈3.5) was inoculated into the 100ml liquid medium, PCA production was increased 5.25 times compared with 120mg/L in original medium. The screened compositions of medium to be optimized were (g/L): glucose 8, fructose 4, glycerol 4, mannitol 4, peptone 11, soybean powder 27.5, soytone 16.3, and KNO3 5. For the purpose of obtaining the maximum PCA yield, we employed statistical experimental design and analysis to carry out a systematical investigation and evaluation. The Plackett-Burman design shown glucose and soytone were the most significant factors among the entire ingredients influencing the PCA yield. The predicted maximum PCA yield of 1250mg/L appeared at glucose 17.81 g/L and soytone 11.47 g/L respectively after the Response Surface Method. 15 of 500ml flasks fermentation, 3L flask fermentation and 10L fermenter fermentation basically verified the results. 1100mg/L PCA production was increased 8.17 times compared with that of in the original medium which was 120mg/L.