Food Engineering / Gıda Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/12

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Author: search.filters.author.Vennapusa, Rami Reddy

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  • Article
    Citation - WoS: 18
    Citation - Scopus: 18
    Surface Energetics To Assess Biomass Attachment Onto Hydrophobic Interaction Adsorbents in Expanded Beds
    (Elsevier Ltd., 2009) Vennapusa, Rami Reddy; Tarı, Canan; Cabrera, Rosa; Fernandez-Lahore, Marcelo
    Cell-to-support interaction and cell-to-cell aggregation phenomena have been studied in a model system composed of intact yeast cells and Phenyl-Streamline adsorbents. 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 the aqueous media provided by operating mobile phases. The effect of pH and ammonium sulphate concentration within the normal operating ranges was evaluated. Calculation indicated that moderate interaction between cell particles and adsorbent beads can develop in the presence of salt. Cell-to-cell aggregation was suspected to occur at high salt concentration and neutral pH. Predictions based on the application of the XDLVO approach were confirmed by independent experimental methods like biomass deposition experiments and laser diffraction spectroscopy. Understanding biomass attachment onto hydrophobic supports can help in alleviating process limitations normally encountered during expanded bed adsorption of bioproducts.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 11
    Colloid Deposition Experiments as a Diagnostic Tool for Biomass Attachment Onto Bioproduct Adsorbent Surfaces
    (John Wiley and Sons Inc., 2008) Tarı, Canan; Vennapusa, Rami Reddy; Cabrera, Rosa B.; Fernandez-Lahore, Marcelo
    Background: Detrimental processing conditions can be expected in any downstream operation where direct contacting between a crude feedstock and a reactive solid phase is supposed to occur. In this paper we have investigated the factors influencing intact yeast cells deposition onto anion and cation exchangers currently utilized for expanded-bed adsorption of biotechnological products. The aim of this study was twofold: (a)to confirm previous findings relating biomass deposition with surface energetics according to the extended Derjaguin, Landau, Verwey and Overbeek theory (XDLVO) theory; and (b) to provide a simple experimental tool to evaluate biomass deposition onto process surfaces. Results: Biomass deposition experiments were performed on an automated workstation utilizing a packedbed format. Two commercial ion exchangers intended for the direct capture of bioproducts in the presence of suspended biological particles were employed. Intact yeast cells in the late exponential phase of growth were selected as model bio-colloids. Cell deposition was systematically evaluated as a function of fluid-phase conductivity and quantitatively expressed as a biomass deposition parameter (α). Conclusion: α ≤ 0.15 was established as a criterion to reflect negligible biomass adhesion to the process support(s). Biomass deposition experiments further confirmed predictions made on the basis of free interfacial energy calculations as per the extended DLVO approach.