You may know kelp as a common seaweed food on our table. As a kind of brown algae with complex sugar compositions, kelp can also be converted into biofuels due to its inherent advantages of no lignin, high growth rate, and no competition with food production for land or fresh water. However, the lack of key bioconversion technology, low level of fermentation efficiency, and incapability of utilizing of various sugars, has limited the development for bioenergy production from brown algae. Thermophiles are regarded as one kind of most promising microorganisms to work on this bioprocess. 

The Microbial Resource Group, led by Professor LI Fuli, from the Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, found a novel thermophilic bacterium for ethanol production from brown algae. 

By using kelp as substrate, the thermophilic community with brown algae fermenting property was obtained. The representative species Alg1 was then isolated, which can simultaneously utilize varying sugar compositions (e.g. mannitol, glucose, and alginate) to produce ethanol with high yield of up to 0.47 g/g-mannitol, 0.44 g/g-glucose, and 0.3 g/g-alginate, respectively. A rational redox balance system under obligate anaerobic condition in fermenting brown algae was revealed through genome and redox analysis. Surprisingly, the strain 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.  Visually, an obvious difference can be observed over brown algae before and after fermentation (Figure 1).  

This work was published in Biotechnology for Biofuels. Dr. JI Shiqi, the first author of the paper, said "To the best of our knowledge, the Alg1 strain we found can produce much higher yield of ethanol than the wild thermophilic strains reported". 

Figure 1. Transmission electron microscope (TEM) and optical microscope images of brown algae samples, unfermented brown algae (a,b,e), and brown algae after fermentation (c,d,f).e,fstained with azaleine (Image by QIBEBT).

Reference: 

Direct Bioconversion of Brown Algae into Ethanol by Thermophilic BacteriumDefluviitalea phaphyphila, Biotechnology for Biofuels, 2016, 9: 81. 

Contact: Prof. LI Fuli 

Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences 

Email: lifl@qibebt.ac.cn