Promotion of medium-chain fatty acids and long-chain alcohols production by zero-valent iron: Effect of particle sizes

Abstract

The effect of zero-valent iron (ZVI) particle size on biological chain elongation (CE) was explored. The addition of ZVI particles with diameters of 50 nm-1000 µm stimulated both medium-chain fatty acids (MCFAs) and long-chain alcohols (LCAs) production, and increased carbon conversion rate of CE process by 2.8–12.2 times. ZVI particle size of 75 µm exhibited the best performance in promoting MCFAs production, achieved the highest MCFAs production of 2164.2 mg/L, which was 11.9 times of control group. ZVI particle size of 1000 µm showed the best performance in stimulating LCAs production, obtained the highest LCAs production of 434.0 mg/L, which was 33.4 times of the control group. Microbial community analysis suggested that different ZVI particle sizes significantly affected genus Clostridium_sensu_stricto_12 and Clostridium_sensu_stricto_7. Functional enzyme analysis revealed that 75 µm ZVI particles induced the strengthened reverse β oxidation pathway, while 1000 µm ZVI particles enhanced the fatty acid biosynthesis pathway.