Dataset Information

Enhanced saccharification of rice straw by overexpression of rice exo-glucanase.

ABSTRACT: BACKGROUND:Efficient production of carbon-neutral biofuels is key to resolving global warming and exhaustion of fossil fuels. Cellulose, which is the most abundant biomass, is physically strong and biochemically stable, and these characteristics lead to difficulty of efficient saccharification of cellulosic compounds for production of fermentable glucose and other sugars. RESULTS:We transformed rice with overexpressing constructs of rice genes encoding each of three classes of cellulases. The exo-glucanase overexpressing plants showed various abnormalities in leaf such as division of leaf blade, crack on leaf surface, excess lacunae in midrib structure and necrotic colour change. The overexpressing plants also showed sterility. Noticeably, these plants showed enhanced saccharification of stems after maturation. These results indicate that overexpression of the exo-glucanase gene brought about various developmental defects associated with modification of cell wall and enhanced saccharification in rice. On the other hand, endo-glucanase-overexpressing plants could not be obtained, and overexpression of ?-glucosidase brought about no effect on plant growth and development. CONCLUSIONS:Our results indicate that genetic engineering of cellulosic biomass plants by overexpressing cellulase genes will be one of the approaches to confer enhanced saccharification ability for efficient production of cellulosic biofuels such as ethanol.

SUBMITTER: Nigorikawa M

PROVIDER: S-EPMC4883724 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Enhanced saccharification of rice straw by overexpression of rice exo-glucanase.

Nigorikawa Mutsumi M Watanabe Aiko A Furukawa Kayoko K Sonoki Tomonori T Ito Yukihiro Y

Rice (New York, N.Y.) 20120628 1

<h4>Background</h4>Efficient production of carbon-neutral biofuels is key to resolving global warming and exhaustion of fossil fuels. Cellulose, which is the most abundant biomass, is physically strong and biochemically stable, and these characteristics lead to difficulty of efficient saccharification of cellulosic compounds for production of fermentable glucose and other sugars.<h4>Results</h4>We transformed rice with overexpressing constructs of rice genes encoding each of three classes of cel ...[more]

PMID: 24279714

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Project description:BACKGROUND: Trichoderma reesei is a widely used industrial strain for cellulase production, but its low yield of ?-glucosidase has prevented its industrial value. In the hydrolysis process of cellulolytic residues by T. reesei, a disaccharide known as cellobiose is produced and accumulates, which inhibits further cellulases production. This problem can be solved by adding ?-glucosidase, which hydrolyzes cellobiose to glucose for fermentation. It is, therefore, of high vvalue to construct T. reesei strains which can produce sufficient ?-glucosidase and other hydrolytic enzymes, especially when those enzymes are capable of tolerating extreme conditions such as high temperature and acidic or alkali pH. RESULTS: We successfully engineered a thermostable ?-glucosidase gene from the fungus Periconia sp. into the genome of T. reesei QM9414 strain. The engineered T. reesei strain showed about 10.5-fold (23.9?IU/mg) higher ?-glucosidase activity compared to the parent strain (2.2 IU/mg) after 24 h of incubation. The transformants also showed very high total cellulase activity (about 39.0 FPU/mg) at 24 h of incubation whereas the parent strain almost did not show any total cellulase activity at 24 h of incubation. The recombinant ?-glucosidase showed to be thermotolerant and remains fully active after two-hour incubation at temperatures as high as 60°C. Additionally, it showed to be active at a wide pH range and maintains about 88% of its maximal activity after four-hour incubation at 25°C in a pH range from 3.0 to 9.0. Enzymatic hydrolysis assay using untreated, NaOH, or Organosolv pretreated barley straw as well as microcrystalline cellulose showed that the transformed T. reesei strains released more reducing sugars compared to the parental strain. CONCLUSIONS: The recombinant T. reesei overexpressing Periconia sp. ?-glucosidase in this study showed higher ?-glucosidase and total cellulase activities within a shorter incubation time (24 h) as well as higher hydrolysis activity using biomass residues. These features suggest that the transformants can be used for ?-glucosidase production as well as improving the biomass conversion using cellulases.

Dataset Information

Enhanced saccharification of rice straw by overexpression of rice exo-glucanase.

Publications

Enhanced saccharification of rice straw by overexpression of rice exo-glucanase.

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