Elucidating the key environmental parameters during the production of ectoines from biogas by mixed methanotrophic consortia

Anaerobic digestion (AD) is a robust biotechnology for the valorisation of organic waste into biogas. However, the rapid decrease in renewable electricity prices requires alternative uses of biogas. In this context, the engineering of innovative platforms for the bio-production of chemicals from CH4 has recently emerged. The extremolyte and osmoprotectant ectoine, with a market price of similar to 1000_/Kg, is the industrial flagship of CH4 based bio-chemicals. This work aimed at optimizing the accumulation of ectoines using mixed microbial consortia enriched from saline environments (a salt lagoon and a salt river) and activated sludge, and biogas as feedstock. The influence of NaCl (0, 3, 6, 9 and 12 %) and Na2WO4 (0, 35 and 70 mu g L-1) concentrations and incubation temperature (15, 25 and 35 degrees C) on the stoichiometry and kinetics of the methanotrophic consortia was investigated. Consortia enriched from activated sludge at 15 degrees C accumulated the highest yields of ectoine and hydroxyectoine at 6 % NaCl (105.0 +/- 27.2 and 24.2 +/- 5.4 mgextremolyte gbiomass 1, respectively). The consortia enriched from the salt lagoon accumulated the highest yield of ectoine and hydroxyectoine at 9 % NaCl (56.6 +/- 2.5 and 51.0 +/- 2.0 mgextremolyte gbiomass 1, respectively) at 25 degrees C. The supplementation of tungsten to the cultivation medium did not impact on the accumulation of ectoines in any of the consortia. A molecular characterization of the enrichments revealed a relative abundance of ectoine-accumulating methanotrophs of 7-16 %, with Methylomicrobium buryatense and Methylomicrobium japanense as the main players in the bioconversion of methane into ectoine.

Automated summary

Anaerobic digestion is a biotechnology for converting organic waste into biogas, but the decreasing renewable electricity prices require alternative uses for biogas. Recent efforts have focused on developing innovative platforms for producing chemicals from CH4, with ectoine being a prominent example. This study aimed to optimize the accumulation of ectoines using mixed microbial consortia from saline environments and activated sludge, with the enrichments showing different yields under varying NaCl concentrations and incubation temperatures.