Evaluation of Growth Characteristics of <I>Euglena gracilis</I> 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/(m 2 ·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.

Bioproducts From Euglena gracilis: Synthesis and Applications

“…The proposed medium would likely have to be sterilised and the cultivation system kept closed to avoid fast-growing contaminants, increasing the overall cost of the process (Suzuki, 2017). The use of wastewater, municipal organic waste, compost or nutrition-rich waste products from the food industry such as potato liquor or dairy effluent could lower the costs by replacing or supplementing the HT growth medium with the additional benefit of potentially bioremediating these effluents (Šantek et al, 2012; Mahapatra et al, 2013; Yadavalli et al, 2014; Torihara and Kishimoto, 2015; Tossavainen et al, 2018).…”

Molecular tools and applications of Euglena gracilis: From biorefineries to bioremediation

“…There is a growing demand for nutrient removal (e.g., nitrogen and phosphorus) from inland waterways such as lakes and ponds to prevent eutrophication. As E. gracilis can utilize water contaminated with high amounts of nitrogen and phosphorus for growth and tolerates high concentrations of heavy metals (Torihara & Kishimoto, 2015), it holds promise for application in various bioremediation settings, one of which is heavy metal remediation discussed below.…”

A Synthetic Biology Perspective on the Bioengineering Tools for an Industrial Microalga: Euglena gracilis

“…It majorly lives in freshwater, is distributed worldwide, and could bloom in ponds, rivers, wastewater, etc. E. gracilis exhibits both animal and plant features with various modes of nutrition, including autotrophy, heterotrophy, and mixotrophy ( Torihara and Kishimoto, 2015 ). As a model microorganism, E. gracilis has been studied extensively in many aspects, such as the development of secondary endosymbiotic chloroplasts, bioremediation of environmental pollutions, and decreasing carbon dioxide emissions, especially the improved harvest of high-value products that people in the market favor ( Klinthong et al, 2015 ; Gissibl et al, 2019 ; Tahira et al, 2019 ).…”