Abstract: The present invention is directed to a process of producing substantially pure lignin from lignocellulosic biomass, which comprises: pre-treating a lignocellulosic feedstock to produce a reactive lignin-carbohydrate mixture; biologically-reacting the carbohydrates in the mixture, separating remaining solids from the liquid fermentation products, and drying the resulting solids to yield a substantially pure lignin product. Optionally, the lignin product may be washed and subjected to a second hydrolysis step. Optionally, the lignin product may be further processed by hydrotreating and/or pyrolysis in order to yield desirable products such as fuel additives.