Ethanol Production and Other Bioproducts by Galactomyces geotrichum from Sugarcane Bagasse Hydrolysate

This study investigated the enzymatic saccharification of alkaline-pretreated sugarcane bagasse (PSB) and the bioconversion of simple sugars from hydrolysates to ethanol and other bioproducts by the yeast Galactomyces geotrichum. The effects of percentage of dry substrate (3 and 10% w/v) and time of hydrolysis (24 and 72 h) in the content of released sugars were evaluated. The concentrations of monosaccharides and total reducing sugars (TRS) were calculated by high-performance liquid chromatography (HPLC) and by 3.5-dinitrosalicylic acid (DNS) method, respectively. The highest concentrations of TRS, glucose and xylose (73.96, 31.78 and 10.85 g/L, respectively) were obtained after the saccharification of 10% of PSB with Cellic CTec3 multi-enzyme cocktail (10 FPU/g cellulose) during 72 h (hydrolysate IV). G. geotrichum UFVJM-R150 fermented both glucose and xylose from the hydrolysates. The most efficient ethanol production was obtained after the fermentation of hydrolysate IV (9.99 g/L of ethanol, volumetric productivity-Q_P of 0.42 g/L.h and yield of ethanol as a function of the substrate-Y_P/S of 0.27 g_ethanol/g_sugar). Besides ethanol, G. geotrichum was also able to produce other high-value chemicals such as isoamyl alcohol and galacturonic acid. This is the first report of the potential of the yeast G. geotrichum to fermentate sugarcane bagasse hydrolysates with the production of important bioproducts to further use by biorefineries.