Rami Reddy Vennapusa

• Common limitations encountered during the direct recovery of bioproducts from an unclarified feedstock are related to the presence of biomass in such processing systems. Biomass related effects can be described as biomass-to-support interaction and cell-to-cell aggregation. In the current thesis work biomass related effects were studied in an important integrated primary unit operation mode viz Expanded bed adsorption (EBA), which was proved to suffer from the detrimental effects by the presence of biomass. Current work involves the investigation and understanding of the biomass interaction and aggregation onto various EBA process surfaces at local or molecular level. In doing so Streamline materialsTM of various chemistries were taken as process surface and intact yeast cell, yeast homogenates, and disrupted bacterial paste were employed as model colloids to understand their deposition and subsequent aggregation. Deposition and aggregation was studied with surface energetics according to XDLVO theory. These predictions based on the application of XDLVO theory were confirmed by independent experimental methods, like biomass deposition experiments and laser diffraction spectroscopy. Biomass components and beaded adsorbents were characterized by contact angle determinations with three diagnostic liquids and zeta potential measurements. Subsequently, free energy of interaction vs. distance profiles between interacting surfaces was calculated in aqueous media provided by its operating mobile phase. The effect of various chromatographic conditions based on the mode of operation was explored in relation to yeast interaction and aggregation. Calculations indicated that the interaction and aggregation is mainly due to the existence of a reversible secondary energy minimum. The extent and depth of pocket varied based on the operating process conditions for different interacting pairs. Understanding biomass-related effects will overcome or at least mitigate the process limitations. Exploring the effect of various types of additives for their ability to inhibit either biomass deposition, cell aggregation, or a combination of both effects, a non ionic polymer PVP 360 was found to alleviate biomass deposition on weak anion exchangers. The predictions made by the XDLVO theory were well correlated with the physicochemical parameter α, in relation to ion exchangers where only interaction is happening. On the other hand a discrete modifications of XDLVO energies was observed with the lump parameter α for hydrophobic and pseudo affinity process surfaces where interaction and aggregation is taking place. Establishing a correlation defined a safe operational windows for EBA process when U ≤ |50| kT and α ≤ 0.15. Fundamental knowledge which could predict feedstock behaviour during primary unit operations of downstream processing would alleviate the current bottleneck during processing of bioproducts.