초록
To improve the sustainability of microalgae as a bioenergy feedstock, lipid-extracted microalgae (LEM) are often further treated by anaerobic digestion (AD). However, the residual chloroform used for extracting lipids as a solvent could inhibit this process, an aspect that has not been studied to date. In this study, the inhibitory effect of chloroform on H<SUB>2</SUB> and CH<SUB>4</SUB> production was investigated by performing batch tests. To prepare the feedstock, Chlorella vulgaris was ultrasonicated and the supernatant was discarded after centrifugation. In case of H<SUB>2</SUB> production, it was found that the H<SUB>2</SUB> yield fell to almost half that of the control (15.6 mL H<SUB>2</SUB>/g COD<SUB>added</SUB>) at 100 mg CHCl<SUB>3</SUB>/L. The reason for the decrease of the H<SUB>2</SUB> yield with the increase of chloroform level was due to the change of metabolites from acetate and butyrate to lactate via a non-hydrogenic reaction. In comparison with H<SUB>2</SUB> production, a much more severe inhibitory effect of chloroform on CH<SUB>4</SUB> production was observed. The inhibitor concentration (IC<SUB>30, 60, and 90</SUB>) on H<SUB>2</SUB> production was 138, 319, and 622 mg CHCl<SUB>3</SUB>/L, respectively, while concentrations of 15, 37, and 86 mg CHCl<SUB>3</SUB>/L were obtained on CH<SUB>4</SUB> production. When the chloroform concentration was ≥25 mg/L on CH<SUB>4</SUB> production, more than 2 g COD/L of organic acids remained, resulting in a decrease of CH<SUB>4</SUB> yield. These findings indicate that the residual chloroform in LEM should be seriously considered to prevent possible microbial inhibition when designing a process for additional energy recovery from microalgae via AD.