The development of "tailored" bioenergy crops is one research area where crop biotechnology can contribute to lowering the cost of cellulose-ethanol production from lignocellulosic biomass. "Tailored" lignocellulosic plant biomass feedstocks with low lignin content could improve cell-wall digestibility and reduce the costs of pretreatment. (Pretreatment is a thermochemical process where chemical agents (in combination with heat) wrench-off the tight lignin wrapping of the plant biomass and expose the cellulose/hemicellulose fibers for further processing to ethanol). Researchers from Purdue University (United States) report that modifying the lignin composition in a model plant, Arabidopsis thaliana, can improve cell-wall digestibility and makes pretreatment more efficient. Lignin is a phenolic polymer containing p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units as building blocks. By modifying the relative abundance of the G-units and S-units in mutant and genetically-modified model plant lines, they showed that pretreatment performance (by liquid hot water addition) was improved. They concluded that "increasing lignin S monomer content through genetic engineering may be a promising approach to increase the efficiency and reduce the cost of biomass to biofuel conversion". The full results are published in the open-access journal, Biotechnology for Biofuels.