Lignin content in original rice straw and solid fractions obtained during each stage of delignification process, as shown in Fig. 1, were measured according to NREL (National Renewable Energy Labora- tory) LAPs (standard Laboratory Analytical Procedures). Lignin fraction in biomass is a sum of AISL (acid insoluble lignin) and ASL (acid soluble lignin). Both, AISL and ASL concentrations were determined according to LAP-003 and 004, respectively.