Evaluation of toxic effect of monoterpene compounds on anaerobic digestion

Monoterpenes are antimicrobial compounds widely distributed in vegetable biomass, whose inhibitory potential for anaerobic digestion is underestimated. In this research, the toxic effect of limonene and fenchone, two of the main monoterpenes present in vegetable biomasses, and those of 4-terpineol, α-terpineol, and p-cymene, compounds described as main metabolites of limonene degradation, have been assessed. Methane production was totally inhibited at dosed of 1000 mg L−1 of fenchone and limonene and at 600 mg L−1 of p-cymene and 4-terpineol. Based on the methane production rate, the inhibition followed the next trend: α-terpineol < < fenchone < limonene ≈ p-cymene < 4-terpineol. Regardless of dosed concentration, monoterpenes were mostly degraded at the end of the experiment (>85%), except p-cymene at 600 mg L−1. Therefore, monoterpenes could entail a high risk of inhibition that can be aggravated by the difficulty to accurately follow their concentration and by the scarce information on their effect on anaerobic process. ; Dra. Angeles Trujillo-Reyes acknowledges to the Pablo de Olavide University and the Santander Bank for her mobility grant to the Pontificia Universidad Católica de Valparaíso, Chile. Dr. Juan Cubero-Cardoso wants to thank Next Generation European Funds and the Ministry of Universities of Spain for funding the Recualificación del Profesorado Universitario system. Dr. Antonio Serrano is grateful to the Economic Transformation, Industry, Knowledge, and Universities Department of the Andalucía Autonomous Government for his Emergia fellowship (EMERGIA20_00114). Dr. David Jeison acknowledges the support provided by CRHIAM centre (ANID/FONDAP/15130015). Funding for open access charge: Universidad de Granada / CBUA. ; Química "Profesor José Carlos Vílchez Martín"