Use of biofuels is regarded as one of powerful trump cards to cope with suspending global warming issue, and therefore getting more and more interest today. Bioethanol is a representative biofuel and produced by means of fermentation using various kinds of biomass resources that are classified into three groups.

Currently, the most economical way to produce ethanol is fermentation of glucose that is contained in juice of sugar cane and its kind, and this method needs only a simple system. There is another process that uses starchy crops as raw materials, where saccharifying enzyme turns starch into glucose. The glucose is subsequently put into fermentation process and turned into bioethanol. Both two methods have been widely adopted in practical use.

A new process for bioethanol production is under development, which utilize waste woody biomass that would not compete with production of edible food crops. Wood and grass materials are made of cellulose, hemi-cellulose and lignin that are strongly bonding together. Consequently, pretreatment technology to dissolve this bonding is required. At present, however, any of pretreatment technology so far developed has proved to be quite costly and far from being used in practice.

A noteworthy report has been published recently as regard to biological decomposition of woody material using microbes such as fungi, which is one of pretreatment methods under research. Termites are thought to be voracious insects that eat houses made of wood. On the other hand, it has been known that termites have special digestive capability in their bowels to dissolve cellulose into glucose.

A national research institute RIKEN has been conducting research on termites since long time ago. January 2010, RIKEN made an announcement that it has obtained a comprehensive set of cellulose-decomposing enzymes (cellulases) from various microbes living in the guts of termites. And that after investigating the genome of the microbes, it has succeeded in clarifying the high-efficiency saccharification system working in termites’ guts. RIKEN also stated that some termite’s genes for producing enzymes has 5 ~ 10 times more strong activity than that of hitherto known enzymes.

Termites are generally regarded as nuisance to human society, but they are in fact beneficial for the nature since termites decompose dead trees, and some 20 % of plant biomass in the nature is decomposed by termites. The clarification of cellulose-decomposition process in termite guts will undoubtedly open the way to establish a new production technology for bioethanol, since this new technology can make it possible to dispense with traditional pretreatment of cellulose, and hence it will be much more energy-efficient and of low cost.

Fig. Different Bioethanol Production Processes and Raw materials

Cf. Website of RIKEN, a press release of the Nikkei