Effective Recovery Of Rhamnoliquids From The Fermentation Broth Of Pseudomonas Aeruginosa By Using A New Technology Of Foam Fractionation

Rhamnolipid is a kind of glycolipid biosurfactant secreted by pseudomonas aeruginosa,and it has non-toxic,non-sensitive and biodegradable characteristics.Rhamnolipid has exhibited potential application in the fields of oil exploitation,green agriculture and medical treatment.However,the high production cost and the difficulty of downstream separation of rhamnolipid limit its large-scale application.Therefore,it has become a research focus on the development of energy saving,environmental protection and high efficiency method for reducing the production cost of rhamnolipid.In this work,the carbon source of medium was first screened.A coupling technology of foam fractionation and acid precipitation was used to separate rhamnolipid from fermentation broth.Finally,ACA microcapsule was used to immobilize the bacteria cells,and the on-line separation of rhamnolipids was realized by fermentation coupled foam fractionation.Firstly,Pseudomonas aeruginosa D1 was expanded in the seed medium for 16 h,and then transferring into the fermentation medium for producing rhamnolipid.Glycerin,soybean oil,cooking oil,lauric acid,lauryl alcohol and liquid paraffin were used as a single carbon source for culturing pseudomonas aeruginosa D1.The cheap cooking oil is suitable for rhamnolipid production was chosen as the suitable carbon source through comparing the fermentation state,fermentation time and yield of rhamnolipid.The optimum carbon source adding amount was 2%.Secondly,the p H of fermentation broth was adjusted for precipitating rhamnolipid.At p H 3.0,the separation rate of rhamnolipid could reach 73.5%.In order to effectively recover the remaining rhamnolipid from the supernatant of fermentation broth,a new foam fractionation column with wedge-shaped components in the horizontal foam phase was developed to strengthen foam drainage.Under the operating conditions of p H 7.0,pore diameter of gas distributor 650 ?m,volumetric air flow rate 60 m L/min and initial loading liquid volume 100 m L,the recovery percentage of rhamnolipid reached 72%.Using the coupling technology of acid precipitation and foam fractionation,the total recovery percentage of rhamnolipid was about 97%.Finally,in order to avoid the foam entrainment of bacterial cells in the process of foam separation,the microcapsule technology was used to immobilize the bacteria cells.Under the conditions of chitosan concentration of 5.0 g/L,chitosan p H6.0 and sodium citrate liquefaction time of 15 min,ACA microcapsules with good performance and stability were prepared.The on-line enrichment of rhamnolipid by fermentation coupling foam separation method reached the enrichment ratio of 32.5 and recovery rate of 84.6% respectively.The method successfully achieved in situ separation of rhamnolipid and could provide a research idea for industrial production of biological surfactants.