Production and separation of pseudomonas aeruginosa rhamnolipids using coupling technology of cyclic fermentation with foam fractionation

Rhamnolipids are widely investigated to control the growth of food pathogenic bacteria as well as repair environmental problems. This work was proposed to in situ recover rhamnolipids from the fermentation medium of Pseudomonas aeruginosa D1 through foam fractionation. The kinetic model of the fermentation process of Pseudomonas aeruginosa was established, solved and tested. The model fitted well with the experimental data. The results showed that the initial addition rhamnolipids concentration of 1.25 g/L had little effect on the growth of bacteria, but could significantly affect the synthesis of rhamnolipids. Under the suitable conditions of volumetric air flow rate 60 mL/min, loading liquid volume 100 mL, pore diameter of gas distributor 160 mu m, the enrichment ratio and the recovery percentage of rhamnolipids reached 4.83 and 75.15%, respectively. Experimental results indicated that the maximum yield of rhamnolipids could be obtained by coupling foam fractionation with fermentation at 42 h, in which the synthesis rate of rhamnolipids was maximal. Moreover, the yield of rhamnolipids per unit volume of fermentation medium was 16.46 g/L, and the yield was 32.63% higher than that of uncoupled operation, and 13.04 and 10.32% higher than those of coupled operation at other fermentation times.