Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 20, 2011
Publication Date: July 18, 2011
Citation: Miranda, C., Sattler, S.E., Sarath, G., Vogel, K.P. 2011. Indirect measurements of Brachiaria brizantha cv. Marandu fermentable cell wall sugars for second generation biofuels production. Annals of the 48th Annual Meeting of the Brazilian Animal Production Society, Belem, PA, Brazil, July 18-21, 2011. Pages 1-3. Interpretive Summary: Bracharia is a tropical grass that has potential use for bioenergy. It is currently used primarily as a forage in tropical grasslands. In a cooperative study, US and Brazilian scientists evaluated the relationship between forage digestibility and biomass sugar composition which is directly related to potential ethanol yields in a biorefinery. The results indicate that the forage quality test, in vitro dry matter digestibility or IVDMD, can be used to estimate potentially fermentable cell wall sugars but a larger set of samples representing a broader range of biomass quality will need to be analyzed to develop better prediction equations.
Technical Abstract: Results of a study conducted to evaluate the possibility of using IVDMD values of B. brizantha cv. Marandu to predict cell wall sugars that would be available in a biorefinery for ethanol production are reported. The study was conducted based on the similarity between rumen enzymes and those used in chemical conversion processes. The study was based on 20 samples, taken from a set of 180 samples collected from a two-year long field experiment, with harvests at rainy and dry season. These samples represent plants of low to medium growth potential and quality. IVDMD was analyzed by NIRS. Glucose, xylose, arabinose and galactose in the hemicelulose, as well as glucose in the cellulose were analyzed by ion exchange liquid chromatography, after pretreatment and extraction with diluted acid. IVDMD values varied from 426 to 646 g.kg-1 of dry mass. Composition range values and Pearson correlations with IVDMD are reported. In the hemicelulose fraction, xylose varied from 148.3 to 218.0 mg g-1, r = 0.69, P<0.001); arabinose (59.0 to 72.5 mg g-1, r = 0.55, P<0.05); galactose (26.9 to 39.9 mg g-1, r = -0,86, P<0.001), glucose varied from 25.8 to 39.8 mg g-1, r = -0.71, P<0.001). In the cellulose only glucose was found in measurable amounts (140.2 to 224.4 mg g-1, r = -0,62, P<0.001). Results indicate that it is possible to use IVDMD to estimate potentially fermentable cell wall sugars contents, but further studies are needed with samples representing larger nutritional and physiological contrasts to validate and develop better prediction equations.