Enhanced biomass production of pseudomonas flourescens for waste water treatment in shake flask and semi industrial scale bioreactor

Abstract

Pseudomonas fluorescens is a biological denitrification bacterium that able to transform of oxidized nitrogen compounds (nitrate and nitrite) into harmless nitrogen gas. Nitrification followed by denitrification is a reliable and economical method for removing nitrogen from wastewater. However, the process is slow and affected by limitation of organic sources. Therefore in order to increase efficiency P. fluorescens as nitrogen removal in the waste water treatment, it is recommended to study medium composition that affects the growth of P. fluorescens for industrial scale cell mass production. Moreover, little information on cell mass production is available. Therefore, the objective of this research is to develop an industrial culture medium and a cultivation strategy for the mass production of P. fluorescens in a semi-industrial scale. At beginning of research, several medium formulations were tested for their cell growth potential. The best medium yielded a cell mass of only 2.08 g L -1 in shake flask cultures and was optimized using a classical approach (changing factors one by one). Sucrose and yeast extract were selected as the best carbon and nitrogen source respectively for the new medium composition. Only 10 g L -1 for sucrose concentration and 3 g L -1 of yeast extract concentration required for cell growth and no significant increase in cell mass for both concentration above than that. Thus, the final cell mass of optimized medium from classical method achieving a maximum of 3.02 g L -1 increased up to 45.19 %. Then optimized medium was applied in bioreactor for batch cultivation by controlled and uncontrolled pH condition. It is found that controlled pH showed 39.56 % more of cell mass compared to uncontrolled pH yielded a cell mass of only 2.78 g L -1. As a result, fermentation with controlled pH gives higher potential of production of cell mass at industrial scale.