Abstract
Mannitol-containing macro algae biomass, such as Ascophyllum nodosum and Laminaria digitata, 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 Clostridia to ferment mannitol and mannitol-containing algal extracts. Screening of the type strains of six genera, Caldanaerobius, Caldanaerobacter, Caldicellulosiruptor, Thermoanaerobacter, Thermobrachium, and Thermoanaerobacterium) 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 Thermoanaerobacter (7 of 16 strains) with yields up to 88% of the theoretical yield in the case of Thermoanaerobacter pseudoethanolicus. Six selected mannitol-degrading strains (all Thermoanaerobacter species) were grown on mannitol extracts prepared from A. nodosum and L. digitata. Five of the strains produced similar amounts of ethanol as compared with ethanol yields from mannitol only. Finally, T. pseudoethanolicus was kinetically monitored using mannitol and mannitol extracts made from two macro algae species, A. nodosum and L. digitata for end-product formation.
Highlights
Due to the worldwide energy crisis and environmental problems associated with the utilization of petroleum products, the need for biofuel production from renewable feedstocks that do not compete with agriculture has been of increased interest over the past several decades (Sánchez and Cardona, 2008; Scully and Orlygsson, 2015)
As a raw material for bioprocessing, brown macro algae have been used for biogas production while for bioethanol production the complexity of the biomass still presents a serious challenge for economic success due to the diversity of carbohydrates present as well as pretreatment methodologies still being in their infancy (Wei et al, 2013; Enquist-Newman et al, 2014; Milledge et al, 2014; Jiang et al, 2016)
The two macro algae species used in the present investigation A. nodosum and L. digitata were analyzed for protein, fat, ash, and total carbohydrates
Summary
Due to the worldwide energy crisis and environmental problems associated with the utilization of petroleum products, the need for biofuel production from renewable feedstocks that do not compete with agriculture has been of increased interest over the past several decades (Sánchez and Cardona, 2008; Scully and Orlygsson, 2015). Brown macro algae have complex carbohydrate composition containing alginate, fucoidan, mannitol, and laminarin (Wei et al, 2013; Xia et al, 2015; Kawai and Murata, 2016). As a raw material for bioprocessing, brown macro algae have been used for biogas production while for bioethanol production the complexity of the biomass still presents a serious challenge for economic success due to the diversity of carbohydrates present as well as pretreatment methodologies still being in their infancy (Wei et al, 2013; Enquist-Newman et al, 2014; Milledge et al, 2014; Jiang et al, 2016)
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