Recebido em 26/4/11; aceito em 11/11/11; publicado na web em 13/1/12 POTENTIAL OF SUGARCANE STRAW FOR ETHANOL PRODUCTION. Sugarcane straw biomass accounts for 1/3 of the energy potential of sugarcane and represents a rich source of sugars. Studies have been intensified for the use of this biomass along with bagasse for the production of cellulosic ethanol. Development of this technological path will allow for taking full advantage of sugarcane, increasing ethanol production without expanding the area cultivated. However, in order for this technology to be viable certain challenges must be overcome, including establishment of appropriate conditions of pretreatment and hydrolysis of these materials for release of fermentable sugars.Keywords: sugarcane straw; lignocelullosic biomass; ethanol. INTRODUÇÃOA iminente escassez das reservas de petróleo, principal fonte energética mundial, juntamente com as preocupações da sociedade com a preservação ambiental, são os principais motivos que levaram os governos a buscarem estratégias para uma maior produção e maior consumo de combustíveis que sejam renováveis e sustentáveis. 1,2 Um dos principais objetivos do uso dos biocombustíveis é a substituição de combustíveis fósseis, permitindo a diminuição da dependência por recursos não renováveis e a redução das emissões de gases de efeito estufa. A queima de combustíveis fósseis representa aproximadamente 82% das emissões dos gases causadores do efeito estufa. 3 Portanto, seja pela questão ambiental global, seja pela importância em reduzir a dependência externa de energia, o etanol de cana-de-açúcar, que já apresenta indicadores ambientais muito positivos quando comparado a outras opções, representa uma alternativa viável na substituição de combustíveis fósseis. 4 O etanol obtido do caldo de cana-de-açúcar (etanol de primeira geração) é, até o momento, o único combustível com capacidade de atender à crescente demanda mundial por energia renovável de baixo custo e de baixo poder poluente. Deve-se considerar que as emissões gasosas com a queima do etanol são da ordem de 60% menores se comparadas às emissões da queima da gasolina, sendo ainda que o do CO 2 emitido é reabsorvido pela própria cana. 5 Atualmente, o etanol é produzido praticamente a partir de matérias-primas sacarinas ou amiláceas, cana-de-açúcar e milho, respectivamente. Entretanto, há um grande esforço da comunidade científica para o desenvolvimento de novos processos economicamente viáveis para o aproveitamento da componente lignocelulósica da biomassa, caso dos resíduos agrícolas (palha e bagaço de cana-de--açúcar, palha de trigo e resíduos de milho) e resíduos florestais (pó e restos de madeira), assim como o capim elefante para produção de etanol combustível (etanol de segunda geração). 6,7 O mais abundante recurso biológico renovável da terra é a biomassa lignocelulósica. 8 Estima-se que somente os EUA têm potencial para produzir mais de 1,3 bilhões de toneladas (base seca) de biomassa por ano. 9 Segundo Zhang, 10 um bilhão de toneladas de biomassa seca produz e...

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Calixarenes, macrocyclic compounds of phenolic units linked by methylene groups at the 2,6-positions, present some of the requirements to serve as platforms for the design and synthesis of biological active compounds. They are also interesting host molecules for chemical biology study purposes. Their basic molecular scaffold has potential ability for molecule recognition; it is promptly synthesized in large amounts, and might be easily modified for maximizing molecular interactions toward relevant guest molecules. Calixarenes present well-defined conformational properties and cavities with molecular dimensions that enable to encapsulate guest drugs. Calixarenes have been shown to have antiviral, antibacterial, antifungal, and anticancer activities (including HIV as target). We provide here an overview of the use of calixarenes either as new chemical entity of distinct biological activities or as host for bioactive guest molecules. The importance of calixarenes for drugs development is discussed. The use of Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) techniques for the study of calixarenes as biological molecule hosts is also described.

Yacon flour has been considered a food with prebiotic potential because of the high levels of fructooligosaccharides, which allows for its use in formulating synbiotic foods. The purpose of this study was to evaluate the effect of yacon flour and probiotic (Bifidobacterium longum) on the modulation of variables related to bone health. Thirty-two Wistar rats were divided into 4 groups: control, yacon flour, diet+B. longum, and yacon flour+B. longum. After euthanasia, the bones were removed for analysis of biomechanical properties (thickness, length, and strength of fracture) and mineral content (Ca, Mg, and P); the cecum was removed for analysis of the microbiota and short-chain fatty acids. Tibia Ca, P, and Mg content was significantly (P<.05) higher in groups fed diet+B. longum, yacon flour+B. longum than in the control group. An increase in fracture strength was observed in the yacon flour (8.1%), diet+B. longum (8.6%), and yacon flour+B. longum (14.6%) in comparison to the control group. Total anaerobe and weight of the cecum were higher (P<.05) in rats consuming the yacon flour diet compared with the other groups. Cecal concentration of propionate was higher in all experimental groups compared with the control (P<.05). Yacon flour in combination with B. longum helped increase the concentration of minerals in bones, an important factor in the prevention of diseases such as osteoporosis.

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Theoretical calculations and the isomeric product composition for a series of eight meta-substituted allyl aryl ethers confirm the reliability of a new (1)H NMR methodology used to predict aromatic Claisen regioselectivity from ground-state conformational preference of the reactant allyloxy group. Frontier HOMO-LUMO intramolecular orbital interactions, a classical approach in predicting reactivity and selectivity for Claisen rearrangements of allyl vinyl ethers, is shown to fail to mimic transition-state orbital interactions for aromatic Claisen rearrangements of meta-substituted allyl aryl ethers. B3LYP/6-31G(d,p) calculations on reactants and transition states are shown, however, to correctly predict the outcome of such aromatic Claisen rearrangements from either the preferential reactant ground-state conformation (theoretical predictions that agree with the NMR measurements) or the less energetic transition state, or both.

This study used both microscopic and biochemical analyses to investigate the possible defense responses induced by acibenzolar-S-methyl (ASM) and potassium phosphite (Phi) in mango plants inoculated with Ceratocystis fimbriata. Disease development was evaluated in the stems of inoculated mango plants and these were examined using fluorescence and light microscopy. High-performance liquid chromatography (HPLC) was used to quantify secondary metabolites in the stem sections. Spraying the plants with ASM and Phi reduced internal necrosis and disease development. The ASM and Phi induced many microscopic defense responses in the stem tissues against C. fimbriata infection. HPLC analysis revealed that the concentrations of two alkaloids (theobromine and 7-methylxanthine) and 10 phenolic compounds (catechin, epicatechin, epigallocatechin, gallic acid, myricetin, p-coumaric acid, p-hydroxybenzoic acid, phloridzin, sinapinic acid, and salicylhydroxamic acid) were higher in the stem tissues of plants sprayed with ASM or Phi than in inoculated control treatment. The concentrations of phenolic compounds were higher in the stem tissues of inoculated plants than in noninoculated plants, while the inverse was observed for alkaloids. Higher concentrations of secondary metabolites in the stem tissues were detected in the early stages of fungal infection, especially in plants treated with inducers. Taken together, the results from the present study clearly support the concept that the phenylpropanoid pathway in the stem tissues of mango plants infected by C. fimbriata can be induced by ASM and Phi.

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