Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Dairy

Morphology, rheology and technology as well as physiology of the viable cells are useful and valuable characteristics used in the identification of any microorganism in order to classify and use in industrial foods. Therefore, characterization of these properties for10 pure strains of LAB (6 cocci & 4 bacilli) used as a major starter cultures was the aim of this work. Selected strains were grown in RSM and broth media (M17 & MRS), examined under SEM and their photography were processed with Image Analysis software SPIP. Detection and quantification of bacterial cells were done using the polygon measure shape.Topographical images revealed spherical or pseudo-spherical structures for cocci strains with height profiles and occur singly, or in pairs, chains and tetrads while that of rod strains showed elongated rod structures (slender rods to cocco-bacilli shapes) and arranged in chains. Cocci cells had a wide range of diameters (0.79-1.51 om) with wide cells perimeters of 2.69 up to 5.54 om. Rod strains had elongation varied between 0.02-0.81 om with great differences within strains. The growth in selective broth media produced cells with higher surfaces areas and volumes being from 0.26 om3to1.82 om3. Some cocci cells showed far away from being a perfect circle (0.639) while others had close to circle shapes. Cocci and rod cells had a different orientation angles. Cell surfaces seems to have heights or extrudes with external boundary was either a sharp outline or a rough surface. Cells hardness and wall thickness had been negatively or positively affected depending on the strain and growing medium. Rheological properties (viscosity, shear stress and torque) recorded different values. Shear stress followed the same trend as viscosity with maximum reached at different times (12 up to17 hrs)

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