Optimization Of The Fermentation Media And Culture Conditions For Flocculant HBF-1 Produced By Marine Halomonas Sp. V3a-1

As the high speed development of the economy and population,the problem of wastewater becomes more and more serious.The chemical flocculants such as the iron, aluminum and the polyacrylamide class flocculants,which are widespread used,not only cause environmental pollution,but also exist latent harm to the human health.In recent years,the study of bioflocculants has attracted wide attention.Since bioflocculants are biodegradable,nontoxic,and produce no secondary pollution,they will be potential replacements for organic synthetic flocculants applied in wastewater treatment,downstream processing,and fermentation processes.The paper has studied the bioflocculant HBF-1 produced by strain Halomonas sp. V3a-1 screened from a hypobenthile sediment sample of the west Pacific Ocean.For depicting the cell growth,bioflocculant-producing and depletion of glucose,the Logistic Equations,Luedeking-Priet are used in quantifying the processing.The bioflocculant-producing dynamics of Halomonas sp.V3a-1 were demonstrated.The models about the strain growth,production of bioflocculant,and consumption of glucose were described.The estimation of the model parameters were confirmed in modeling process based on the fermentation data.Through the comparison of experimental data and the corresponding calculated values from the models,we found that the two group data joint well.These models offered the evidences for large scale production of HBF-1.The carbon sources and nitrogen sources were choosed by single factor experiments firstly.Then the media and growth conditions of Halomonas sp.V3a-1 were optimized by means of orthogonal test based on single factor experiments.The results showed that it was more suitable for the strain's growth and the bioflocculant's excreted using glucose and sucrose as a complex carbon source,and the ratio of them was 3 to 2.If corn powder and urea were used as a complex nitrogen source,the culture would have higher flocculating activity with low cost.The optimal production medium was:6.0 g/L glucose, 4.0 g/L sucrose,2.0 g/L maizena,2.0 g/L urea,1.0 g/L MgSO₄·7H₂O,20.0 g/L NaCl,2.0 g/L KH₂PO₄ and 5.0 g/L K₂HPO₄.The optimal culture conditions were as follows:the temp was 28℃,the initial pH was 7.0,the inoculum size was 3%,and the rotation speed of the shaker was 160 rpm.And the flocculating activity of culture broth could achieve 99.8%under the optimized conditions.In order to increase the yield of HBF-1 further,the fed-batch technology were researched based on the optimized culture conditions by orthogonal tests.The results showed that when the carbon source were feed at 18-24 h,the yields of HBF-1 were raised 9.1-12.7%.And when the nitrogen source as urea was fed at 24-30 h,the yields of HBF-1 were raised 4.5-8.4%.And the cell growth has improved much under the two fed-batch technology.