Maximizing Sugar Yields from Lignocellulosic Biofuel Feedstocks

The concept of "Polydispersity of Biomass Recalcitrance" (PPBR) has been introduced by an international team of scientists, as a parameter for assessing "processability" of lignocellulosic bioenergy crops into sugars for biofuel-ethanol production.

The main carbohydrate fractions of lignocellulosic biofuel feedstocks (cellulose and hemicellulose) are usually broken down (i.e. "pretreated/saccharified") into their component sugars (glucose and xylose), which are subsequently fermented to ethanol. Determination of the optimum conditions for the cellulose/hemicellulose conversion into sugars is usually done using the total sugar yield (i.e., the sum of glucose and xylose liberated) as the response variable. Thus, only one optimum condition is obtained for both cellulose and hemicellulose conversions.

However, the international scientific team (from the University of Wisconsin, The University of Florida, the Forest Products Laboratory of United States Department of Agriculture, and the South China University of Technology) believes that cellulose and hemicelluloses exhibit different responses to pretreatment, and must be optimized individually. Hemicelluloses require less harsher conditions for conversion into sugars, and easily degrade under more extreme conditions. Celluloses on the other hand are more difficult to break down, and require harsher conditions.

This difference in the "pretreatment/saccharification" response of cellulose and hemicelluloses can be considered as biomass property and has been given the term, "Polydispersity of Plant Biomass Recalcitrance" (or PPBR) by the researchers. In their study, they (1) explored ways to quantify the PPBR, and (2) evaluate the effects of PPBR on pretreatment optimization. The researchers were able to show that PPBR can be a useful predictor of the suitability of an energy crop for biochemical conversion to sugars.

The full results are published in the journal, Bioenergy Research (URL above).