Utilisation of an electro-optical method to investigate the amidase activity of microbial cells

The electro-optical (EO) properties of a microbial cell suspension of Brevibacterium sp. strain 13 PA were examined during acrylamide and acrylic acid metabolism and during culture of cells in a mineral medium without added carbon sources. The dependence of the suspension turbidity changes due to cellular orientation on the frequency of an orienting electric field (orientational spectra, OSs) over the range of 10–10000 kHz were used. Alterations in the OSs, depending on cellular amidase activity, were recorded during growth with acrylamide as the role source of carbon. However, no amidase activity was observed in cells growing with acrylic acid as the sole carbon source. Growth on the carbon-free mineral medium resulted in a reduction in amidase activity. It is apparent that the OS changes reflect the corresponding changes in cell polarisability, which may be associated with acrylamide hydrolysis. The data generated from these studies can be taken as a basis for the EO determination of the enzyme activity of microbial biocatalysts.