Development of dilute sulfuric acid pretreatment method for the enhancement of xylose fermentability

Abstract Dilute acid pretreatment of sorghum stalks was performed for the characteristic xylulosic ethanol production using Pichia stipitis . In this regard, various pretreatment parameters were studied for the maximum xylose production with minimized xylose decomposition. As a result, 89% of xylan conversion was attained along with 22 mg of xylose decomposition at 121 °C with 0.2 M sulfuric acid for 120 min. In addition to this, prehydrolyzate liquors were detoxified with calcium hydroxide [Ca(OH) 2 ] at different pH levels (i.e., 8.5–11.5) to investigate the fermentative inhibitors removal and their impact on xylulosic ethanol production. Consequently, the highest theoretical ethanol yield (91%) was achieved during the fermentation of prehydrolyzate detoxified at pH 11.5. Moreover, 0.46 g p /g s ethanol yield and 0.48 g/L/h ethanol productivity was achieved within 24 h incubation time of Pichia stipits NCIM 3498.