Elucidating the influence of environmental factors on biogas-based polyhydroxybutyrate production by Methylocystis hirsuta CSC1

• Published in: The Science of the total environment Vol. 706; p. 135136
• Main Authors: Rodríguez, Yadira, Firmino, Paulo Igor Milen, Arnáiz, Esther, Lebrero, Raquel, Muñoz, Raúl
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2020
• Subjects: Biofuels; Biogas valorization; Bioreactors; Methane; Methane conversion; Methanotrophs; Methylocystaceae; Methylocystis hirsuta; Microbial cell factories; Polyhydroxybutyrate production; Polyhydroxybutyrate production; Microbial cell factories; Methanotrophs; Biogas valorization; Methylocystis hirsuta; Methane conversion
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.135136

[Display omitted] •M. hirsuta CSC1 was a suitable cell factory for PHB from biogas under N limitation.•The maximum PHB content (45 wt%) was reached at an O2:CH4 ratio of 2:1.•PHB synthesis at 25 °C was higher than at 15 and 37 °C.•NO3– as N source supported a superior PHB accumulation compared to NH4+. The valorization of biogas as a feedstock for the generation of added-value bioproducts will play a key role on the sustainability of anaerobic digestion. The present work assessed the influence of key environmental parameters (O2:CH4 ratio, temperature and nitrogen source) on the growth and polyhydroxybutyrate (PHB) synthesis under nitrogen limiting conditions of the type II methanotroph Methylocystis hirsuta CSC1 using biogas as a feedstock. The O2:CH4 ratios tested (1:1, 1.5:1 and 2:1) did not affect significantly M. hirsuta CSC1 growth yields (~5 g TSS mol−1 CH4), although lower CH4 removal rates were reached under O2-limiting conditions (ratio 1:1). The highest PHB content (45 wt%) was achieved at a ratio 2:1 and was threefold higher than those obtained at lower ratios (~15 wt%). The increase in temperature from 15 to 25 °C resulted in increases in the growth yield (from 5 to 6 g TSS mol−1 CH4) and PHB content (from 32 to 40 wt%). Conversely, the lowest PHB content (30 wt%) was reached at 37 °C, together with a negligible growth under nutrient sufficient conditions. The nitrogen source also played a key role on both M. hirsuta CSC1 growth and PHB synthesis. Thus, ammonium resulted in the highest growth yield (7 g TSS mol−1 CH4), although the maximum PHB content was achieved when biomass was previously grown in nitrate as the nitrogen source (41 wt%). Nitrite exerted an inhibitory effect on M. hirsuta CSC1 growth.