252.
Converting lipid-extracted microalgal wastes to methane (CH
4) via anaerobic digestion (AD) has the potential to make microalgae-based biodiesel platform more sustainable. However, it is apparent that remaining
n-hexane (C
6H
14) from lipid extraction could inhibit metabolic pathway of methanogens. To test an inhibitory influence of residual
n-hexane, this study conducted a series of batch AD by mixing lipid-extracted
Chlorella vulgaris with a wide range of
n-hexane concentration (~10 g chemical oxygen demand (COD)/L). Experimental results show that the inhibition of
n-hexane on CH
4 yield was negligible up to 2 g COD/L and inhibition to methanogenesis became significant when it was higher than 4 g COD/L based on quantitative mass balance. Inhibition threshold was about 4 g COD/L of
n-hexane. Analytical result of microbial community profile revealed that dominance of alkane-degrading sulfate-reducing bacteria (SRB) and syntrophic bacteria increased, while that of methanogens sharply dropped as
n-hexane concentration increased. These findings offer a useful guideline of threshold
n-hexane concentration and microbial community shift for the AD of lipid-extracted microalgal wastes.
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