Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering at KAIST and Professor Kyung-Jin Kim of Kyungpook National University cooperated to reveal the structure and characteristics of Thiolase, a key enzyme used in the production of bio-butanol.

Bio-butanol is regarded as one of the most efficient next generation biofuels. This biofuel is known to have more outstanding features compared to the widely used bio-ethanol: the energy density of bio-butanol is 29.2 MJ, which is similar to that of petrol (32MJ) and 48% higher than that of bio-ethanol (19.6MJ). Furthermore, bio-butanol is not affected by the food supply because it is extracted from inedible biomass such as wood, hay, and algae. One of the biggest advantages of bio-butanol is that it is applicable to existing gasoline engines because it resembles petrol in heat of vaporization, air fuel ratio, and octane number.

Bio-butanol can be produced from the bacteria Clostridium but the mechanism behind its production is yet to be fully studied. Clostridium is an obligate anaerobe that has Gram-positive characteristics. Since 1861, when Louis Pasteur discovered that butanol can be produced from the Clostridium strain, scientists have tried to harness the bacteria to produce not only butanol but also acetone. However, due to the complexity in its metabolic pathway and lack of technology to manipulate the pathway, improving the strain faces many obstacles.

Nevertheless, in this research, Professor Lee’s research team succeeded in revealing the three dimensional molecular structure of thiolase using Pohang light source. Thiolase is a key enzyme in producing bio-butanol because it synthesizes acetoacetyl-CoA through a series of condensation reactions. This reaction is pivotal because this produces four carbon chains, which comprise of butanol along with one alcohol chain. More importantly, the research team discovered a redox switch that is particular to thiolase. Furthermore, they confirmed the functionality of this redox switch using systems metabolic engineering such as virtual cell modeling.

Using the redox switch, the research team produced a mutant enzyme with increased performance. The enzyme then altered the metabolic pathway so that the production of bio-butanol is also enhanced significantly.

Professor Lee explained that this research "unveiled the structure and mechanism of a key enzyme in synthesizing bio-butanol" and expects to “further apply our findings to build a more efficient metabolic pathway to produce bio-butanol.” This research was published online on Nature Communications.