An improved method for preparing microorganism laden alginate bead specimens for accurate Scanning Electron Microscope examination

Abstract

The distribution of biomass encapsulated within alginate beads can be examined using a Scanning Electron Microscope (SEM). Existing methods for the preparation of suitable specimens are extremely time consuming, involving fixing of samples with glutaraldehyde, dehydrating with successive acetone washings and Iinal drying using a critical point technique. These preparations are necessary to avoid signigcaut specimen shrinkage, however, the resultant specimens are sometimes difficult to analyse using an SEM or light microscope. A reliable quick method has been developed where alginate specimens are directly mounted using a water based adhesive, then dried under controlled conditious. These specimens were found to be robust enough for SEM processing and gave true measurements of the original alginate beads iucluding microorganism orientation.

Surfactant‐mediated formation of alginate layers at the water‐air interface

“…In this work, we present investigations on polysaccharide solutions of sodium alginate with different cationic surfactants over a broad concentration range. Because of their environmental compatibility, biopolymers like gum acacia, chitosan, or alginate are found in pharmaceutical and food applications, in cosmetic products, and in detergents . Nevertheless, the use of biopolymers makes the study of polymer‐surfactant interactions more complicated because of a broader variation of the polymer chains (molecular weight, monomer sequence, branching, etc).…”

“…Because of their environmental compatibility, biopolymers like gum acacia, chitosan, or alginate are found in pharmaceutical and food applications, in cosmetic products, and in detergents. [34][35][36][37][38][39][40][41][42][43][44] Nevertheless, the use of biopolymers makes the study of polymer-surfactant interactions more complicated because of a broader variation of the polymer chains (molecular weight, monomer sequence, branching, etc). However, there are some important studies, [45][46][47][48] for example, the interesting hyaluronate-cationic surfactant complexes, which are investigated by Thalberg and Lindman, 49 or the carboxymethylcellulose-cationic surfactant complexes investigated by Langevin et al 50 Other important examples are the chitosan-anionic carboxylate surfactants studied by Chiappisi and Gradzielski 51 ; a good overview of the neglected class of surfactants with multiresponsive properties is given in Chiappisi.…”

Magneto-responsive alginate capsules

“…Encapsulation of substances in biocompatible matrices is of outstanding interest in the food industry and cosmetics. These technologies are also important in pharmaceutical and medical applications such as drug delivery and cell encapsulation [1][2][3][4]. For these environmentally compatible encapsulation techniques gels of calcium alginate are frequently used because alginate is a cheap, non-toxic, easily polymerizable biopolymer with tuneable release properties [5,6].…”

“…Upon compression, the force is measured as a function of the gap between the two parallel plates. For small deformations, the curve of force versus displacement is linear and can be fitted to calculate the elastic modulus by equation (1).…”

“…In equation (1), F is the force, E is the elastic modulus, h the thickness of the membrane, R the radius of the capsule, υ the Poisson ratio and d the displacement.…”