Topochemical Lignin Distribution of Sugarcane Cell Wall and Enzymatic Hydrolyzability for Biofuels Processing

Scientists from the Universidade de São Paulo (Brazil), and Federal Research Institute for Rural Areas, Forestry and Fisheries (Germany) investigated the topochemical distribution of lignin and some aromatic compounds in sugarcane, in an attempt to obtain useful information on the recalcitrance of specific cells. "Recalcitrance" is one property of (lignocellulosic) biomass which make the biomass more difficult for processing into biofuels, particularly during the saccharification process.

Saccharification is the breakdown of cellulose polymers in the biomass into simple sugars for ethanol fermentation. Recalcitrance is attributed to lignin compounds in biomass; these molecules wrap around the cellulose polymers and limit cellulose accessibility to enzymatic saccharification. By examining topochemical distribution of lignin compounds in lignocellulosics, strategies might be considered for reducing biomass recalcitrance for improved processing of the biomass to biofuels. The scientists used "cellular ultraviolet (UV) microspectrophotometry (UMSP) to topochemically detect lignin and hydroxycinnamic acids in individual fiber, vessel and parenchyma cell walls of untreated and chlorite-treated sugar cane".

Some of the results of their study are: (1) UV measurements of untreated sugarcane fiber cell walls showed absorbance spectra typical of grass lignin; (2) highest levels of lignification were found to be in the cell walls of vessels, followed by fibers and parenchyma; (3) Chlorite treatment of pith cells did not enhance cellulose conversion; but chlorite treatment of the rind cells resulted in the significant removal of hydroxycinnamic acids and lignin, resulting in marked enhancement of cellulose conversion by cellulases.

The full results are published in the open access journal, Biotechnology for Biofuels (URL above).