Lignocellulosic materials are renewable resources for bioethanol production from sugars. Pretreatment of lignocellulosic materials is a necessary element in bioconversion of cellulosic and hemicellulosic sugars to ethanol. Removal of lignin from lignocellulosic biomass was optimized by laccase-mediator system. A 300 mg sample of sweet sorghum and switchgrass in a 50 mL Erlenmeyer flask was subjected to 20 mL reaction mixture of laccase or laccase mediator system (LMS).  Activity of laccase enzyme in the reaction mixture was 10 units mL^-1 along with varying concentrations of one of the three mediators; HBT (1-hydroxybenzotriazole), violuric acid (5-isonitrosobarbituric acid), and ABTS (2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid). The concentration of HBT and ABTS in the reaction mixture was 0, 0.13, 0.25, 0.31, 0.63, 1.25, and 1.88 mM and violuric acid concentration was 0.31, 0.63, 1.25, and 1.88 mM to optimize the mediator concentration for maximum lignin removal. A 5-8% and 5-14% lignin removal was observed sweet sorghum and switchgrass, respectively after 24 h treatment with laccase-ABTS system. A 25.5% lignin removal at 1.88 mM HBT and 24% at 1.25 mM VA after 24 h treatment was observed in sweet sorghum. Similarly, in switchgrass a 28% lignin removal at 0.63 mM VA in combination with laccase was observed after 24 h treatment. A slight loss is structural sugars were observed at treatments with enzymatic treatments. The optimum mediator concentration for maximum removal of lignin changed with mediators and lignocellulosic biomass.