Comparative data on effects of leading pretreatments and enzyme loadings and formulations on sugar yields from different switchgrass sources

Dilute sulfuric acid (DA), sulfur dioxide (SO2), liquid hot water (LHW), soaking in aqueous ammonia (SAA), ammonia fiber expansion (AFEX), and lime pretreatments were applied to Alamo, Dacotah, and Shawnee switchgrass. Application of the same analytical methods and material balance approaches facilitated meaningful comparisons of glucose and xylose yields from combined pretreatment and enzymatic hydrolysis. Use of a common supply of cellulase, beta-glucosidase, and xylanase also eased comparisons. All pretreatments enhanced sugar recovery from pretreatment and subsequent enzymatic hydrolysis substantially compared to untreated switchgrass. Adding beta-glucosidase was effective early in enzymatic hydrolysis while cellobiose levels were high but had limited effect on longer term yields at the enzyme loadings applied. Adding xylanase improved yields most for higher pH pretreatments where more xylan was left in the solids. Harvest time had more impact on performance than switchgrass variety, and microscopy showed changes in different features could impact performance by different pretreatments.

► Comparative data were developed on leading pretreatments for the first time.
► All pretreatments greatly enhanced sugar yields from pretreatment and hydrolysis.
► Enzyme formulations to increase sugar yields can change with pretreatment type.
► Harvest time had more impact on performance than switchgrass variety.
► Microscopy showed different features may impact performance from each pretreatment.