Screening and optimization for bioflocculant production by isolated Enterobacter cloacae under batch and fed-batch cultication
Poonsuk Prasertsan, Assoc. Prof., D. of Industrial Biotech., F. of Agro-Industry, PSU.
Santad Wichienchot, M.Sc. Student in Biotech., PSU.
Weerapan Dermlim, M.Sc. Student in Biotech., PSU.
Doelle H. W., Prof., D. of Microbiology, The U. of Queensland, St. Lucia, Australia
Corresponding e-mail : ppoonsuk@ratree.psu.ac.th
Grant : Graduate School, PSU.
Presented : The World Congress on Biotechnology and the 11th International Biotechnology
Symposium and Exhibition, 3-8 September 2000, ICC, Berlin, Germany
Key words : screening, optimization, bioflocculant, Enterobacter cloacae, batch, fed-batch
A total of 188 polymer-producing bacterial strains were isolated from recycled sludge of seafood wastewater treatment plants. The strain selected from shake-flask culture based on its highest viscous culture broth exhibiting the flocculating activity was identified to be Enterobacter cloacae. The effect of medium composition on the production of polymer from the isolate was investigated. Among the carbon sources (1%) tested, galactose and sucrose gave higher polymer yields (2.50 and 2.45 g/l, respectively) compared to maltose, fructose and glucose. Surcrose was chosen due to its lower cost and the optimum concentration was found to be 3%, giving the polymer yield of 2.72 g/l after 72 h cultivation. Several sources of inorganic nitrogen and an organic nitrogen tested had no influence on the polymer yield. The optimum concentration of yeast extract was 0.05%. The optimum initial pH was 7.0 and higher yield was achieved under pH controlled (at 7.0) condition. An increase in the aeration rate from 0.05 vvm to 2.0 vvm could elevated the polymer yield to 4.8 g/l while increase of the agitation speed reduced the polymer yield. Further increase of polymer concentration could be achieved from fed-batch culture with the addition of 10% sucrose every three days of cultivation. The polymer yield increased to 6.19 g/l which was 2.5 times higher than the initial value.
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