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Physicochemical surface properties of brewing yeast influencing their immobilization onto spent grains in a continuous reactor
Author(s) -
Brányik Tomáš,
Vicente António,
Oliveira Rosário,
Teixeira José
Publication year - 2004
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.20217
Subject(s) - brewing , yeast , adhesion , adsorption , chemistry , chemical engineering , flocculation , saccharomyces cerevisiae , fermentation , biochemistry , organic chemistry , engineering
Immobilization of brewing yeast onto a cellulose‐based carrier obtained from spent grains, a brewing byproduct, by acid/base treatment has been studied in a continuously operating bubble‐column reactor. The aim of this work was to study the mechanisms of brewing yeast immobilization onto spent grain particles through the information on physicochemical surface properties of brewing yeast and spent grain particles. Three mechanisms of brewing yeast immobilization onto spent grains carrier were proposed: cell‐carrier adhesion, cell‐cell attachment, and cell adsorption (accumulation) inside natural shelters (carrier's surface roughness). The possibility of stable cell‐carrier adhesion regarding the free energy of interaction was proved and the relative importance of long‐range forces (Derjaguin‐Landau‐Verwey‐Overbeek theory) and interfacial free energies was discussed. As for the cell‐cell attachment leading to a multilayer yeast immobilization, a physicochemical interaction through localized hydrophobic regions on cell surface was hypothesized. However, neither flocculation nor chain formation mechanism can be excluded so far. The adsorption of brewing yeast inside sufficiently large crevices (pores) was documented with photomicrographs. A positive effect of higher dilution rate and increased hydrophobicity of base‐treated spent grains on the yeast immobilization rate has also been found. © 2004 Wiley Periodicals, Inc.