The main objective of this study was to allocate and evaluate the most optimum condition to prepare the chitosan and chitosan nanoparticles that will, subsequently, give the best physicochemical characterization regarding the nanoparticles' size and surface morphology. Chitosan from the exoskeleton wastes of Procambarus clarkii with degree of deacetylation 87% was extracted. Viscometry indicated that the obtained chitosan had a low molecular weight that can be useful in many applications. Chitosan nanoparticles were prepared by using different concentrations of chitosan and the polyanion sodium tripolyphosphate (TPP). For the determination of the optimum condition for the prepared chitosan nanoparticles, three different ratios of chitosan to the polyanion TPP were used, 1:1, 3:1, and 1:3. A novel nanoparticle system composed of low molecular weight chitosan was successfully prepared by the ionotropic gelation technique under an aqueous-based condition. The physicochemical characteristics of chitosan and chitosan nanoparticles were elucidated by Fourier-transform IR spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis, scanning electron microscopy, transmission electron microscopy, and zeta potential. The best physicochemical characteristics were obtained by adding chitosan to TPP in a ratio of 1:1. The small particle size and narrow range distribution of the obtained chitosan nanoparticles may increase their chance for easy and efficient manipulation for several applications in various fields. In addition, the obtained positively charged chitosan nanoparticles can be used for the delivery of negatively charged compounds.

The study was designed to evaluate the effect of dietary L-lysine supplementation on growth performance and feed utilization of African catfish fingerlings fed diet containing high levels of slaughterhouse poultry by-product meal (SPB). Control diet (CD) without amino acid supplementation or SPB inclusion contained 40% of fish meal (FM) and 20% of soybean meal (SBM), four isonitrogenous and isocaloric diets formulated to represent two levels of SPB (50% and 75%) with two levels of L-lysine supplementation (0.0 and 1.0%), SPB_50%^0.0, SPB_50%^1.0, SPB_75%^0.0 and SPB_75%^1.0, where the subscripts and superscripts refer to the replacement level of FM with SPB and L-lysine supplementation level respectively. Growth performance and feed utilization in terms of final body weight (FBW), weight gain (WG), feed intake (FI), and specific growth rate (SGR) tended to decrease as SPB levels increased from 50% to 75% with or without L-lysine supplementation. Protein retention (PR) was not significantly different between fish fed CD and those fed SPB_50%^0.0. Energy retention (ER) was not significantly different between fish fed CD and those fed SPB_50%^0.0 and SPB_75%^1.0. Lipid, protein, moisture, and ash of fish fed the experimental diets were not statistically significantly different than the control diet. The partial replacement of FM at the rate 50% and 75% with SPB is possible in diets for African catfish, especially with 1% L-lysine supplementation, and could match growth performance of FM diets, as well as minimize feed cost and improve profitability.