Evaluation of Growth Characteristics of Euglena gracilis for Microalgal Biomass Production Using Wastewater

Abstract

Recently, fossil fuel depletion and global warming have become serious problems in the world. In order to solve these problems, renewable energy has attracted much attention. Here, a microalga, Euglena gracilis (E.gracilis), was focused on as a renewable biomass energy source. In our idea, E. gracilis biomass produced using nutrients in wastewater is mixed with sewage sludge, and anaerobically digested for methane recovery. It is considered that microorganisms and suspended solids in wastewater may have a negative impact against the growth of E. gracilis. Accordingly, their effect on the growth of E. gracilis was discussed in this research. Three types of culture media, supernatant fluid of wastewater, suspended solids-free wastewater, and suspended solids and microorganisms-free wastewater, were used for the cultivation test. The culturing conditions were a temperature of 25°C and photosynthetically active radiation of 98.2 μmol/(m²•s). As a result, E. gracilis was able to increase in wastewater, though both microorganisms and suspended solids gave a negative influence. Since the negative effect of suspended solids was stronger than that of microorganisms, an introduction of a pre-removal process of suspended solids would be favored for the microalgal biomass production in wastewater.