Paramylon production from heterotrophic cultivation of Euglena gracilis in two different industrial byproducts: Corn steep liquor and brewer's spent grain

Euglena gracilis is a promising microalga containing valuable intracellular components such as paramylon with notable immune-functionality. For economic paramylon production, industrial byproducts can be considered as low-priced media. In this study, corn steep liquor and brewers' spent grain were employed as cost-effective media for paramylon production. The paramylon content and yield for E. gracilis cultivated using the corn steep liquor (46.3% w/w and 0.17 g/g) were higher than those using the brewer's spent grain (32.3% w/w and 0.11 g/g). Under the optimized cultural condition of 5% diluted corn steep liquor at an initial pH of 3.5 and temperature of 25 degrees C, E. gracilis showed the competitive paramylon content (54.2%) and productivity (0.45 g/L/d) compared to those of other studies even without an additional carbon source. This study is the first report on applicability of brewers' spent grain to bioproduction of E. gracilis but it needs further investigation for productivity enhancement. Thus we suggest using corn steep liquor as a sole substrate for E. gracilis is a promising way which shows competent productivity even without any additional substrate such as glucose or fructose. Application of the corn steep liquor as an industrial byproduct can be a successful strategy for efficient and economic paramylon production.