10-16: Diluted acid and liquid hot water pretreatment for the production of ethanol by enzymatic hydrolysis from sugarcane bagasse

The technology for the production of ethanol from lignocellulosic biomass by enzymatic hydrolysis has shown significant progress in recent years, and today it is considered to be competitive for the production of fuels coming from non-renewable sources.  These scientific and engineering advances have resulted in the emergence of the first available commercial technologies accompanied by demonstration and industrial projects.  A stage of vital importance in the efficiency of the biochemical route is the pretreatment step, in which the major components of biomass (cellulose, hemicellulose and lignin) are separated to enhance the subsequent enzymatic hydrolysis. Many technologies that involve the use of chemicals such as acids, bases and solvents have been proposed and tested for this pretreatment step.  However, it is evident that the use of chemicals needs to be lowered to diminish the impact on the environment and the production of toxins that inhibit the downstream fermentation process.  Here, we present the results of a study for the production of ethanol from sugarcane bagasse using liquid hot water (LHW) and dilute sulfuric acid in concentrations lower than 1% that are easily manageable and have a low environmental impact.  The tests were performed at temperatures ranging between 140 °C and 200 °C.  To evaluate the production of inhibitors during the pretreatment in the hydrolysates, a growth test was performed for each sample using a Saccharomyces cerevisiae yeast strain commonly used for fermentation.