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\bibitem{Kerckhof_etal2021} {\textquotedblleft}\textit{From biogas and hydrogen to microbial protein through co-cultivation of methane and hydrogen oxidizing bacteria}{\textquotedblright}. Kerckhof F-M, Sakarika M, Van Giel M, Muys M, Vermeir P, De Vrieze J, Vlaeminck SE, Rabaey K, Boon N, Frontiers in Bioengineering and Biotechnology \textbf{9}, 733753 (2021).   http://doi.org/10.3389/FBIOE.2021.733753

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