RESUMO
The conversion of biomass into ethanol using fast, cheap, and efficient methodologies to disintegrate and hydrolyse the lignocellulosic biomass is the major challenge of the production of the second-generation ethanol. This revision describes the most relevant advances on the conversion process of lignocellulose materials into ethanol, development of new xylose-fermenting strains of Saccharomyces cerevisiae using classical and modern genetic tools and strategies, elucidation of the expression of some complex industrial phenotypes, tolerance mechanisms of S. cerevisiae to lignocellulosic inhibitors, monitoring and strategies to improve fermentation processes. In the last decade, numerous engineered pentose-fermenting yeasts have been developed using molecular biology tools. The increase in the tolerance of S. cerevisiae to inhibitors is still an important issue to be exploited. As the industrial systems of ethanol production operate under non-sterile conditions, microbial subpopulations are generated, depending on the operational conditions and the levels of contaminants. Among the most critical requirements for production of the second-generation ethanol is the reduction in the levels of toxic by-products of the lignocellulosic hydrolysates and the production of low-cost and efficient cellulosic enzymes. A number of procedures have been established for the conversion of lignocellulosic materials into ethanol, but none of them are completely satisfactory when process time, costs, and efficiency are considered.
Assuntos
Reatores Biológicos/microbiologia , Etanol/metabolismo , Engenharia Genética/métodos , Lignina/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Fermentação , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/efeitos dos fármacosRESUMO
Comments are made and new insights are provided on the key role played by endogenous and exogenouselectric fields, where the former starts and conducts the repairing chain, while the latter is able to scramblethe completion of the repair process and, as a consequence, may have important potential as a radiationsensitizer for clinical application.
Assuntos
DNA , Radiação Ionizante , RadioterapiaRESUMO
The effects of gamma radiation from (60)Co and (137)Cs on DNA in aqueous solution are studied experimentally. Using an improved plasmid purification protocol and improved electrophoretic gel analysis techniques provided results with relatively small uncertainties. The results are compared with both theoretical and experimental results. In particular, the results obtained here are discussed in the light of recent discussion on supposed differences of the effects induced by gamma radiation from (60)Co and (137)Cs. We find that the effects of both types of gamma radiation are similar.