Separation of lignocellulosic hydrolyzates by polymer induced flocculation and tangential flow microfiltration

Lignocellulosic hydrolyzates produced by the hydrothermal treatment of wood chips contain hemicellulose sugars, acetic acid and significant quantities of inhibitory components. The separation of fermentable sugars from it constitutes an important step in biorefinery processes. Inhibitors such as lignin can interfere with the enzyme activity and hinder the hydrolysis of oligomers. They also severely impact the fermentation processes downstream due to their toxic effects on microbes. Colloidal particles not only inhibit the fermentation activities of microorganisms but also foul any filtration membranes used for separation and purification of extracts.;The separation of inhibitory colloidal (lignin and its derivatives) components by polymer-induced flocculation by cationic and nonionic polymers was studied. Cationic (PEI, CPAM, pDADMAC) and nonionic (PEO) polymers and polyelectrolytes (Alum) were applied to study the separation of colloidal particles by flocculation followed by sedimentation. The dynamics of flocculation and mechanism of individual polymer for adsorption of particles were investigated in this study. Pilot plant studies using PEO polymer and 1000 kg of wood extract were conducted to study the impact for the process operations to develop the design of bioethanol plant.;Microfiltration of biomass hydrolyzates were performed by using ceramic micro filters of 0.2um and 10nm pore size. This study helped in investigating the kinetics of permeates fluxes at different trans-membrane pressure. The kinetics of the flux decay appears to indicate pore blocking and development of external fouling layers. Under the most severe case of fouling, xylose concentrations in permeate dropped to less than one fifth of the feed values.