الفهرس 
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Abstract
This study was carried out in the laboratory of Agric. Biochemistry Department at the Faculty of Agriculture, Zagazig University, Egypt, to make some studies on the formation and disintegration of microbial Biofilm. The aim of this study is to know the definition of biofilm and its properties and describe the importance of it and disadvantages. Biofilm was studied from Staphylococcus aureus in addition to know the factors affecting on increasing of formation of biofilm. Also the factors affecting on preventing from formation. The study was adding some of chitosan types on S. aureus with using some quantities and qualitative methods and Light microscope. Crustacean waste is one of the most severe issues, posing significant environmental and health risks. This study aims to improve managing marine waste by isolating chitosan from Procambarus clarkii through devising a new methodology, incorporating technical steps, e.g., washing, decolorization and deacetylation steps under reflexive condenser, and dialysis purification. A comparison was made between the prepared P.clarkii chitosan and four types of shrimp chitosans, including ”Commercial, High, Low, and Nano chitosan. The obtained chitosan has a low molecular weight and viscosity compared to the commercial shrimp chitosan, used in various applications. P.clarkii chitosan was prepared in high quality from a cheap source, as its color and quality were better than those of the commercial shrimp chitosan. Analysis of the different chitosan samples with Fourier transform infrared spectroscopy (FTIR), atomic force microscopy, Raman spectrum referred indicated high similarity between the chitosan different types, regardless of its source. The new methodology has succeeded in extracting chitosan from P.clarkii in good a quality and high purity, achieving 89 % deacetylation, high solubility, high purity, and medium molecular weight. Evaluating the quality traits indicated the excellence of the chitosan prepared from P.clarkii, especially in color, viscosity, and antioxidant activity, nominating it for different food applications.