Conversion of C6 sugar in detoxified diluted-acid sugarcane bagasse cellulosic hydrolysate using Scheffersomyces stipitis NRRL Y-7124

Second-generation ethanol production has been studied to increase the production of this biofuel mainly through environmentally sustainable processes. For the use of cellulosic fraction of plant biomass is necessary deconstruction of cellulosic matrix which has been studied by enzymatic or chemical hydrolysis. Acid hydrolysis with H₂SO₄ results in cellulosic hydrolysate which requires treatment for reducing the concentration of some compounds liberated during hydrolysis process which are inhibitory to microbial metabolism. Thus, it is necessary to use micro-organisms not only good producers of ethanol, but that can tolerate toxic, since detoxification processes may be expensive or even not allow total removal of toxic. Conversion of glucose into ethanol in diluted-acid sugarcane bagasse cellulosic hydrolysate was investigated using Scheffersomyces (Pichia) stipitis. Cellulosic hydrolysate after diluted sulfuric acid treatment (155°C, 10 minutes), composed of glucose (60 g l^-1) and inhibitors such as hydroxymethylfurfural, furfural and phenols at concentrations of 0.47, 0.03 and 18.15 g l^-1, respectively, was detoxified using a pH adjustment/activated charcoal method, obtained a reduction around 45% of inhibitors compounds. This hydrolysate was supplemented with nutrients and employed as fermentation medium (initial pH adjusted to 5.5) in Erlenmeyer flasks incubated at 30ºC, 200 rpm for 72 hours. The fermentation exhibited cell growth of 11.48 g l^-1 and ethanol concentration of 16.81 g l^-1, corresponding to yield of 0.46 g g^-1 and productivity of 0.23 g l^-1h^-1. The results indicate the advantage of to use S. stipitis in bioprocess with diluted-acid sugarcane bagasse cellulosic hydrolysate considering the presence of the toxic compounds.