Adhesion of Lactobacillus amylovorus to Insoluble and Derivatized Cornstarch Granules

Abstract

Approximately 70% of the cells in a suspension of the amylolytic bacterium Lactobacillus amylovorus bind to cornstarch granules within 30 min at 25°C. More than 60% of the bound bacteria were removed by formaldehyde (2%) or glycine (1 M) at pH 2.0. More than 90% of the bound bacteria were removed by MgCl 2 (2 M; pH 7.0). Binding of L. amylovorus to cornstarch was inhibited in heat-killed cells and in cells that had been pretreated with glutaraldehyde, formaldehyde, sodium azide, trypsin, or 1% soluble potato starch. Bacterial binding to cornstarch appeared to correlate with both the concentration of cornstarch in the suspension and the amylose content in the granules. The ability of L. amylovorus to adhere to cornstarch granules was reduced for granules that had been extracted with HCl-ethanol, HCl-methanol, HCl-propanol, or HCl-butanol. Chemical derivatization of cornstarch resulted in a wide variety of adhesion responses by these bacteria. For example, 2- O -butyl starch (degree of substitution, 0.09) enhanced adhesion, whereas two palmitate starches (degree of substitution, 0.48 and 0.09) exhibited reduced adhesion activities. 2- O -(2-hydroxybutyl) starch and starch-poly(ethylene-co-acrylic acid) ester showed adhesion activities similar to those of the nonderivatized starch controls.