Optimization of Growth Medium and Fed-Batch Cultivation Using Different Feeding Strategies for Production of Acinetobacter Sp. : A Biological Phosphorus Removal

Acinetobacter sp. has been reported previously in their role to enhance the removal of biological phosphorus and heavy metal when introduced in waste water treatment. This is an importance characteristics to be used in remediating the waste water instead of depend on naturally present of microbes. Therefore, high densities of Acinetobacter sp. to function in the bioremediation treatment are needed. The objective of this study is to optimize the production medium and bioprocessing condition for high biomass production of Acinetobacter sp. in a semi-industrial scale 16-L bioreactor. In this research, six different production media were screened to determine the most potent formulation for cell growth. The cell mass production of 2.54 g L^-1 was obtained from shake flask cultures of the best medium with sucrose as the carbon source. This medium was then optimized using statistical approach of response surface methodology. Growth kinetic study of statistical optimized medium gives maximal cell mass of 5.58 gL^-1. During batch cultures of Acinetobacter sp. in the bioreactor 16-L under un-controlled and control pH, the cell mass production is 7.91 gL^-1 and 5.70 gL^-1 respectively indicating by pH drop from 7.0 to 6.0. Unfortunately, cultivation under un-controlled pH and dissolved oxygen cell mass was increased up to 156.06 % after 16-18 hours of cultivation. In conclusion, the growth of Acinetobacter sp. showing the cell mass production rate of 0.23 g L^-1 h^-1 under un-controlled pH when compared with controlled pH cultivation only 0.12 g L^-1 h^-1. Nonetheless, the cell mass was increased when fed-batch cultivations was conducted under controlled dissolved oxygen at 30 % with uncontrolled pH condition. The cell mass production was increased up to 73.19 % (51.60 gL^-1) when constantly fed with full medium composition of optimized medium when compared feeding with mono-carbon solution.

KEYWORD: wastewater treatment, phosphate removal, medium optimization, processing condition, bioreactor, Acinetobacter sp.