Isolation And Optimization Of Culture Conditions Of Biosurfactant-Producing Bacterium

Biosurfactants have the characteristics of high surface-activity,structural diversity,low toxicity,biodegradability and eco-friendly.Biosurfactants can be widely used in oil exploitation,medical services,food industry,environmental modification and many other fields.Therefore,the research and development of biosurfactants have important significance.In the present study,five strains were isolated from the biosurfactant-producing bacterium of bacterial contamination Ochrobactrum sp.DGG-1-3 by the method of enrichment cultivation,plate separation,flask culture and measuring emulsifying activity and surface tension of the culture broth.The fermentation broth of strain 1#had high emulsifying activity and emulsifying index E24 was 54%,whose surface tension decreased from 65mN/m to 50mN/m.Ochrobactrum sp.l#was capable of utilizing carbohydrate(sucrose,maltose,starch)and hydrocarbon(tridecane,liquid paraffin,pentacosane,dotriacontane)for cell growth and bioemulsifier production with carbohydrate as carbon source.The cell density reached the highest when sucrose and liquid paraffin were used as carbon source respectively.The emulsifying index of the fermentation broth was 54%when source and maltose was used as carbon source respectively.During fermentation,the emulsification index of the fermentation broth reached the maximum on the fourth day with sucrose as carbon source,while the emulsifying index of the fermentation broth reached the maximum on the fifth day with maltose as carbon source.Ochrobactrum sp.l#was capable of utilizing organic nitrogen source(peptone,beef extract,yeast extract,corn syrup,soybean flour,soybean meal hydrolyzed)and inorganic nitrogen source(sodium nitrate,potassium nitrate,ammonium chloride,ammonium sulfate,ammonium nitrate)for cell growth and utilizing inorganic nitrogen source for bioemulsifier production.Comparision the effect of nitrogen source(sodium nitrate,ammonium sulfate,ammonium nitrate)at the same level of nitrogen element mole and at the same weight concentration on biosufactant.It was showed that the method of adding the nitrogen source of same weight concentration,exploring the effect of nitrogen source on biosurfactant fermentation was inaccurate and not objective.The result was found that when added nitrogen source at the same level of nitrogen element mole,using sodium nitrate was the most efficient nitrogen source for Ochrobactrum sp.1#to produce bioemulsifier,and the emulsifying index of the fermentation broth was 54%on the fourth day,when added nitrogen source at the same weight concentration,using ammonium nitrate and ammonium sulfate as nitrogen source respectively,the emulsifying index of the fermentation broth improve remarkable was 48%on the third day.Considering the lower cost of ammonium nitrate compared with sodium nitrate,using ammonium nitrate as nitrogen source was more appropriate.