|(200808_A)||August 8, 2008|
Development of Technology for Producing Bioethanol from Nonfood Materials Using Super Koji
Gekkeikan Research Institute is making progress in the development of basic technology for the production of bioethanol from paddy straw, chaff, waste wood and other nonfood plant materials. One major achievement is the development of technology for the mass production of cellulolytic enzymes (enzymes capable of breaking down the plant cellulose that comprises the raw material) through the solid-state culture of koji mold, a microorganism used in sake brewing. The way that koji mold produces enzymes that liquefy starch and convert it to sugar while multiplying on steamed rice, a solid, served as a hint for development of the technology.
The research was conducted jointly with researchers from Kobe University and Osaka University from 2005 as part of a High Efficiency Bioenergy Conversion Project established by NEDO (New Energy and Industrial Technology Development Organization).
The results of this research will be announced on August 28, 2008, at the 2008 Annual Meeting of the Society for Biotechnology, Japan.
Because cellulose, the major structural component of plants, is composed of chains of glucose, bioethanol can be produced by breaking down these chains and then using yeast to ferment the resulting glucose. Cellulose is, however, chemically stable and has a very robust structure. Weakening this structure to enable it to be broken down into glucose currently requires pretreatment using chemical agents such as sulfuric acid or high-temperature, high-pressure water. Because such methods involve liquefaction using large amounts of water followed by fermentation and distillation, production requires a great amount of energy and the apparatus takes up a lot of space.
Gekkeikan Research Institute is accordingly developing a system that holds out promise for reducing water requirements and energy required for distillation by enabling (1) solid-state breakdown of the raw plant material, (2) fermentation, and (3) recovery of the resulting ethanol at normal temperature and pressure. This particular research focused on the first step, namely the development of technology for enabling more efficient solid-state breakdown of the raw plant material through the solid-state culture of koji mold to mass-produce cellulolytic enzymes. More specifically, a new promoter that powerfully expresses cellulolytic enzymes has been identified in the chromosomes of koji mold. The name “super koji” has been attached to strains of koji mold equipped with this attribute.
By greatly enhancing the production of cellulolytic enzymes, the solid-state culture of super koji can serve as an alternative pretreatment method for breaking down the cellulose of the raw plant material into glucose, which can then be fermented by yeast to produce ethanol.
Even if super koji only partially breaks down plant cellulose into glucose, it is effective enough that a “super yeast” developed by Gekkeikan Research Institute can be used to directly produce ethanol from the partially pretreated material.
With the aim of applying this technology to commercial production, Gekkeikan Research Institute is examining possibilities for further developing super koji to make it even more effective at mass-producing cellulolytic enzymes, and for combining it with super yeast to create a production system in which all processes are driven by microorganisms.
Gekkeikan hopes that this application of microorganism and enzyme utilization technology and fermentation technology rooted in Japanese sake brewing for the production of bioethanol will contribute to the resolution of environmental issues.
◆ About super yeast
Sake yeast is renowned for its high alcohol yield, and super yeast is a sake yeast into which koji mold genes that produce cellulolytic enzymes have been introduced so that the enzymes are densely displayed on the surface of the yeast cells.
Because super yeast combines the capabilities of koji mold, which converts the cellulose starch (cellooligosaccharide) into sugar (glucose), with that of yeast, which ferments sugar (glucose), it can produce ethanol by itself from pretreated cellulose.
Super yeast was developed as a result of research conducted jointly with researchers from Kobe University, Kyoto University and Tohoku University over the space of three years from 2004 as part of an Innovative Technology Development Research Project established by Japan Science and Technology Agency (JST).
This achievement was announced on March 28, 2008, at the 2008 Annual Meeting of the Japan Society for Bioscience, and Agrochemistry (JSBBA).
◆About Gekkeikan Research Institute
The Institute started out as the Okura Sake Brewing Research Institute, founded by Tsunekichi Okura, the company's 11th successor, in 1909. It was renamed the Gekkeikan Research Institute in 1990, and now conducts both basic research in sake brewing and a broad range of biotechnological research to develop new products and technologies. The Institute is located in Fushimi-ku, Kyoto, Japan, and is headed by director Yoji Hata.