(567ap) Concentration of Fermentable Sugars within a Lignocellulosic Biomass Hydrolysate by Reverse Osmosis: Effect of Membrane and Hydrolysate Properties and Operating Conditions

Gautam, A., South Dakota School of Mines and Technology
Gilcrease, P. C., South Dakota School of Mines & Technology
Christopher, L. P., South Dakota School of Mines & Technology
Menkhaus, T., South Dakota School of Mines and Technology

Plant biomass, containing lignin, cellulose, and hemicellulose, is one of the most sustainable and abundant sources of fuels and materials available to humans, and in particular for the production of sustainable fuels such as bioethanol. An example of this is wood chips from Ponderosa Pine, which after pretreatment and enzymatic hydrolysis consists of a slurry containing fermentable sugars. Unfortunately, due in large part to the limited solids loading capacity of many pretreatment and hydrolysis operations, the concentration of sugars is relatively low. Thus, concentrating the sugars prior to fermentation can lead to more efficient production and purification of bioethanol. Perhaps the most commonly used method for concentrating sugars in other industries (i.e., fruit juice) is evaporation. However, this process is highly energy intensive and may cause degradation of sugars. In this project reverse osmosis is used as a sugars concentration method, which has low energy consumption, and can produce a high quality sugar stream for fermentation. A range of reverse osmosis membranes were tested that exhibited different chemistries and pore-sizes, and performance evaluation was assessed by measuring permeate flux and retention (yield) of sugars. Both pure sugar solutions as well as real hydrolysates from ponderosa pine were analyzed, along with different feed properties (solids concentrations, pH, etc) and operating pressures. Membranes were evaluated using spectroscopic and microscopic techniques before and after processing to assess fouling regimes and fouling components. Optimal membrane, hydrolysate, and operating properties will be discussed to provide direction for tailoring reverse osmosis materials specifically for operations within a lignocellulosic biorefinery.