title: Direct bioconversion of brown algae into ethanol by thermophilic bacterium Defluviitalea phaphyphila.
abstract: BACKGROUND
  Brown algae are promising feedstocks for biofuel production with inherent advantages of no structural lignin, high growth rate, and no competition for land and fresh water. However, it is difficult for one microorganism to convert all components of brown algae with different oxidoreduction potentials to ethanol. Defluviitalea phaphyphila Alg1 is the first characterized thermophilic bacterium capable of direct utilization of brown algae.
  
  
  RESULTS
  Defluviitalea phaphyphila Alg1 can simultaneously utilize mannitol, glucose, and alginate to produce ethanol, and high ethanol yields of 0.47 g/g-mannitol, 0.44 g/g-glucose, and 0.3 g/g-alginate were obtained. A rational redox balance system under obligate anaerobic condition in fermenting brown algae was revealed in D. phaphyphila Alg1 through genome and redox analysis. The excess reducing equivalents produced from mannitol metabolism were equilibrated by oxidizing forces from alginate assimilation. Furthermore, D. phaphyphila Alg1 can directly utilize unpretreated kelp powder, and 10 g/L of ethanol was accumulated within 72 h with an ethanol yield of 0.25 g/g-kelp. Microscopic observation further demonstrated the deconstruction process of brown algae cell by D. phaphyphila Alg1.
  
  
  CONCLUSIONS
  The integrated biomass deconstruction system of D. phaphyphila Alg1, as well as its high ethanol yield, provided us an excellent alternative for brown algae bioconversion at elevated temperature.
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101 People's Republic of China.
authors.forename: Shi-Qi
authors.initials: SQ
authors.lastname: Ji
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101 People's Republic of China.
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101 People's Republic of China.
authors.forename: Ming
authors.initials: M
authors.lastname: Lu
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, 266101 People's Republic of China.
authors.forename: Fu-Li
authors.initials: FL
authors.lastname: Li
keywords: Bioethanol; Brown algae; Defluviitalea phaphyphila; Marine thermophile; Redox balance