Development of cultivation process for biomass production from Ettlia sp.

Abstract

In recent decades, climate change has been striking the globe and renewable energy sources have become necessary. Biomass has been spotlighted to solve global warming and microalgal biomass especially is gaining attention with advantages regarding food-ethics and deforestation. In this study, a process cultivating a microalga species, namely Ettlia sp. YC001, was statistically optimized. The optimization increased biomass and lipid productivities by 4.9-fold and 2.4-fold, respectively. Subsequently, two feedstocks, i.e., Helianthus tuberosus and algal residue were utilized as alternative nutrient sources. They were hydrolyzed to generate low-cost medium which resulted in biomass and lipid with the same productivity. Furthermore, a sequential hydrolysis process was developed to utilize both feedstocks efficiently. Additionally, an analogous techno-economic analysis for both processes using the optimized medium and low-cost medium was conducted to examine the effectiveness of the developed processes. Hydrolysate medium decreased two-thirds and three-fourths of required operational expenditures to produce Ettlia sp. biomass and lipid, respectively. Lastly, the fructose utilization pathway of Ettlia sp. was analyzed with RNA expression levels of genes related to sugar transportation and the glycolysis pathway. The results showed that the glycolysis pathway of the species is up-regulated under the presence of fructose, and STF11, a hypothetical fructose transporter, transported fructose into cells.