On the elimination of artefactual effects in assessing the structure of calcium alginate cell immobilization gels

The structure of calcium alginate cell immobilization gels has been examined by scanning and transmission electron microscopy. The presence of an alginate coating around the extrude alginate fibres reduced the loss of cells from the immobilized state provided that strict nutrient controls were observed. The constraining alginate coating may be retained for > 500 h under normal operational conditions. The alginate structure within the extruded fibres (4% w/v alginate, 10% w/v Saccharomyces cerevisiae) remained unchanged during the course of a 500 h continuous ethanol fermentation and revealed a pore size within the alginate matrix, usually less than 90 nm. Inappropriate electron microscopy preparation prior to examination may erroneously indicately the alginate matrix to be a macroporous structure. To reduce artefactual effects the alginate structure should only be revealed prior to critical point drying and not at an earlier stage in the preparation for electron microscopy.