Monday, May 4, 2009
9-30
Ethanol Production from Sorghum Grain [Sorghum bicolor (L.) Moench]: Optimization of The Enzymatic Hydrolysis and Evaluation of The Hydrolysate Fermentability
Sorghum is a poaceae originally from Africa which is listed as the fifth cereal most cultived in the world. It is cultivated between the soybean harvesting season in some areas of Brazil and has showed great potential in ethanol production besides having wide adaptability, rapid growth (cicle from 90 to 120 days), and it is tolerant to drought, water logging, soil salinity and acidity toxicity. Also it is more resistent to hydric stress than corn. According to CONAB, in 2007 Sorghum production was 1.6 billion tons in Brazil. The main objective of the present work was to study ethanol production from Sorghum grains [Sorghum bicolor (L.) Moench]. Initially starch enzymatic hydrolysis was optimized using comercial alpha amylases and glycoamylases, considering particle size, solid:liquid ratio and enzyme load as variables. The hydrolysate, in its optimum conditions, was used to produce ethanol, batchwise in a Biostat B reactor, using an industrial strain of Saccharomyces cerevisiae as the fermentative agent. The bioprocess was monitored and its kinetic profile of alcohol production and the consumption of substrate were constructed during 36 hours. The optimum conditions of hydrolysis was as follows: particle size of 1mm, solid:liquid ratio of 1:3 and enzyme load of 20 mcL of alpha amylase and 40 mcL of glycoamylase per g of grain. The maximum ethanol concentration produced was 117 g/L, corresponding to 28 g of ethanol/100 g of Sorghum in 29 hours of fermentation.
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