A biofuel is a fuel that is produced from living organisms, most often referring to plants or plant-derived materials. Plant fixes atmospheric CO₂ via photosynthesis to produce polysaccharides, such as cellulose and hemicellulose. Because biofuels are produced from the plant-derived polysaccharides, CO₂ does not increase when biofuels are used (combusted), which refers to the concept of carbon neutrality. Thus, use of biofuels is an effective way to combat against the global climate change by reducing CO₂ emission. Nonfood-based biomass including rice straw, corn stover, forest thinning residues are promising resources for biofuel production since use of nonfood-based biomass does not compete with food production with respect to land use. There are two technical hurdles to realize biofuels from nonfood biomass: 1) technology for efficient conversion of pentose to biofuel, 2) mitigation of fermentation inhibition by organic compounds (aromatics, organic acids and furans) derived from nonfood biomass. Although polysaccharides composed of nonfood biomass contain pentose sugars (xylose and arabinose) as well as hexose sugars (glucose, mannose and galactose), microorganisms currently used in industrial bioprocess are incapable of utilizing pentose sugars, leading to low yield of biofuels. Inhibitory compounds are produced in a thermochemical treatment step (referred to pretreatment) of nonfood biomass, but this step is required for efficient enzymatic saccharification of biomass. These inhibitory compounds cause low yield and productivity of bioprocess.

Our bioprocess, so-called growth-arrested bioprocess solved these technical hurdles. Thanks to independence of microbial growth for biofuel production, the growth-arrested bioprocess maintains productivity even in the presence of the inhibitory compounds. We developed genetically-engineered strain of Corynebacterium glutamicum that is capable of utilizing pentose and hexose simultaneously and efficiently. We continue to improve the growth-arrested bioprocess by metabolic engineering and process engineering to realize biorefinery.

• Ethanol
• Butanol