Enhancing mesophilic methanogenesis in oleate-rich environments through optimized micro-aeration pretreatment.

Abstract

Micro-aeration pretreatment has emerged as a promising technology for improving the performance of anaerobic bioreactors in the treatment of lipid-rich organic waste, particularly in mitigating the accumulation of long-chain fatty acids (LCFAs). Micro-aeration intensity is a critical factor in optimizing substrate hydrolysis and methanogenesis efficiency. In this study, optimal micro-aeration intensities for acetoclastic (30 mL-air/g-COD) and overall methanogenesis (7.5 mL-air/g-COD) were initially determined using acetate and glucose as substrates, respectively. Subsequently, the addition of 0.5 mM oleate (a typical LCFA) increased cumulative methane production by 22.1 % when acetate was used as the substrate after 30 mL-air/g-COD micro-aeration pretreatment. Conversely, it decreased cumulative methane production by 17.3 % when glucose was used as the substrate after 7.5 mL-air/g-COD micro-aeration pretreatment. Additionally, the population of facultative hydrolysis microorganisms, such as the genus Pseudomonas, increased by 25.7 % and 27.8 % when acetate and glucose were used as substrates, respectively. Furthermore, the predominant methane-producing archaea, including the genus Methanosarcina, increased by 27.3 % when acetate was used as the substrate, while the genus Methanosaeta decreased by 65.3 % when glucose was used as the substrate. Collectively, these findings provide insights into the methanogenesis pathway under optimal micro-aeration pretreatment conditions, guiding future research in this field.