Screening Of Rhamnolipid Producing Strains And Optimization Of Culture Conditions

Rhamnolipid is a kind of glycolipid biosurfactants with strong surface activityand emulsifying ability, which can be completely biodegradable and has potentialapplication in the bioremediation of petroleum exploitation, agricultural production,food, medicine and other fields. Rhamnolipid can be produced by microbialfermentation method, and it has advantages of mild fermentation process, lowrequirements for the equipment, wide and low prize source for raw materials. With thedevelopment of society, clean, safe, and efficient rhamnolipid gets people’s moreattentions. At present, the researches on rhamnolipid production are deepened gradually,and have made some progress. However, due to the low rhamnolipid yield andimmature industrial production technology, production of rhamnolipid by microbialfermentation still remains in the shake flask fermentation stage. In this paper, thescreening of the rhamnolipid-producing mutant strains, optimization of fermentationconditions and construction of the kinetics model was studied. The main results are asfollows.A mutant strain SFZ-37with high rhamnolipid yield was obtained by themutagenetic treatments of ultra violet (UV) and atmospheric and room temperatureplasma (ARTP) on the basis of a strain SFV-7which was stored in our laboratory. Afterthe mutagenesis, the rhamnolipid yield of mutant strain SFZ-37could reach6.4g/L andthe increase was70.6%compared with the original strain.Furthermore, the culture medium and the fermentation conditions of strain SFZ-37were optimized by single-factor experiments. The optimal culture medium forrhamnolipid production were as follows (g/L): glycerol30, corn steep liquor6,potassium phosphate monobasic5.71, disodium hydrogen phosphate2.29, magnesiumsulphate0.4; inoculum age24h, inoculum size5%(v/v), temperature30℃, broth’svolume35mL/250mL in shake flask, inital pH7.0, culture time96h. Under theoptimum conditions, the rhamnolipid yield of strain SFZ-37could reach12.59g/L,which increased by96.72%than the parent strain.Based on the experimental data of batch fermentation in5L magnetic stirringfermentation reactor by Pseudomonas aeruginosa SFZ-37, the kinetic model of cellgrowth, product formation and substrate consumption was established. The non-linefitting was employed to model the kinetics of fermentation by software OriginPro8.0.The results indicated that the kinetic model could be used to describe the relationship of cell growth, product formation and substrate consumption during the process of batchfermentation.