AUTHOR=Chades Theo , Scully Sean M. , Ingvadottir Eva M. , Orlygsson Johann 

TITLE=Fermentation of Mannitol Extracts From Brown Macro Algae by Thermophilic Clostridia

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01931

DOI=10.3389/fmicb.2018.01931

ISSN=1664-302X

ABSTRACT=<p>Mannitol-containing macro algae biomass, such as <italic>Ascophyllum nodosum</italic> and <italic>Laminaria digitata</italic>, are a potential feedstock for the production of biofuels such as bioethanol. The purpose of this work was to evaluate the ability of thermophilic anaerobes within Class <italic>Clostridia</italic> to ferment mannitol and mannitol-containing algal extracts. Screening of the type strains of six genera, <italic>Caldanaerobius, Caldanaerobacter, Caldicellulosiruptor, Thermoanaerobacter, Thermobrachium</italic>, and <italic>Thermoanaerobacterium</italic>) was conducted on 20 mM mannitol and revealed that 11 of 41 strains could utilize mannitol with ethanol being the dominant end-product. Mannitol utilization seems to be most common within the genus of <italic>Thermoanaerobacter</italic> (7 of 16 strains) with yields up to 88% of the theoretical yield in the case of <italic>Thermoanaerobacter pseudoethanolicus</italic>. Six selected mannitol-degrading strains (all <italic>Thermoanaerobacter</italic> species) were grown on mannitol extracts prepared from <italic>A. nodosum</italic> and <italic>L. digitata</italic>. Five of the strains produced similar amounts of ethanol as compared with ethanol yields from mannitol only. Finally, <italic>T. pseudoethanolicus</italic> was kinetically monitored using mannitol and mannitol extracts made from two macro algae species, <italic>A. nodosum</italic> and <italic>L. digitata</italic> for end-product formation.</p>