Comparison of different pretreatment methods based on residual lignin effect on the enzymatic hydrolysis of switchgrass

Three different pretreatment methods for switchgrass were studied. Aqueous sodium hydroxide (0.5–10% w/v, 90 °C, 1 h), dilute H2SO4 (0.5–6.0% v/v, 121 °C, 1 h) and hot water (100 °C, 1 h) were employed in this study to determine how each method affected the digestibility of switchgrass during enzymatic hydrolysis. Switchgrass pre-treated with 0.5% w/v sodium hydroxide generally produced glucose in higher concentrations than sulfuric acid and hot water pre-treated samples. SEM studies on the pre-treated samples revealed a great deal of pore formation in the NaOH pre-treated samples and little or no physical changes on the acid and hot water pre-treated samples. Lignin analysis carried out on the pre-treated samples showed a considerable decrease in lignin content in the NaOH pre-treated samples and only a slight decrease in lignin content for the other pretreatment methods studied.