This study was conducted to determine lysine requirement in laying hens, using plasma free lysine levels as a response criterion. The basal diet used was based on corn- corn gluten meal soybean meal, and contained 0.58% lysine, Nine graded levels of lysine (0.04, 0.08, 0.12, 0.16, 0.2,0.24,0.28,0.32,0.36%) were added to the basal diet. Each experimental diet was fed to 48 laying hens in a randomized complete design with 4 replicates in each treatment. Broken-line method was employed for estimation of lysine requirement. Dietary lysine levels exerted a significant effect on egg weight, egg mass output, feed intake (P<0.01), and feed conversation ratio (P<0.05), but did not significantly affect egg production. Based on egg mass output, feed conversion ratio and plasma free lysine responses, lysine requirements were estimated at 675, 790 and 785 mg per hen -day; respectively. The results suggest that plasma free lysine could be a precise indicator (R2=0.96) for determining lysine requirement in laying hens. In conclusion, based on the results of this experiment, daily lysine requirement of laying hens during peak egg production was estimated at 785-790 mg per hen-day.

Drug resistance has limited the synthesis of new antibiotics. Therefore, the use of compounds that do not have drug resistance has been considered. Antimicrobial peptides are among the compounds for which drug resistance has not been reported. On the other hand, it has been found that the activity of these compounds is less than that of antibiotics. Therefore, the design of appropriate antimicrobial peptides is challenging. To address this challenge, efforts have been made to understand their mechanism of action. However, their mechanism of action is not well understood. In this work, the interaction of two cyclic and linear antimicrobial peptides with sodium dodecyl sulfate micelles as cell membrane mimetics method has been studied by molecular dynamics simulation. The micellar radius of gyration shows good agreement with the experimental results and the results of other simulations performed. Calculation of the conformational factor shows that cyclic antimicrobial peptide has a greater affinity for interaction with micelles. Charged and aromatic residues are involved in the interaction of cyclic antimicrobial peptides with micelles. Whereas, only charged residues are effective in the interaction of the linear antimicrobial peptides with micelle.

The optimization of adsorption-based operations requires an accurate model to represent the separation process. In the present study, single-component adsorption data of L-lysine on its imprinted polymer were fitted to Freundlich, Langmuir-type and Jovanovic-type models. L-Lysine imprinted polymer (LLIP) was prepared by free radical solution polymerization. The best estimate of the parameters of these models by regression analysis was obtained. The statistical analysis of results showed that the experimental data fit the Jovanovic-Freundlich mode, better than other models in terms off value. The best prediction of retention capacity equal to 0.186 mmol lysine per g of LLIP, which is the nearest value to the experimental data, was obtained by applying the Jovanovic model.

Lysine is nutritionally essential for humans and animals. It cannot be synthesized biologically in body. Children and growing animals have a high requirement of lysine, since it is needed for bone formation. Therefore, it must be added to food and feed supplement to improve the protein quality. In addition, lysine has some pharmaceutical applications in the formulation of diets with balanced amino acid composition. Chemical, enzymatic and biotechnological processes have been used to synthesize lysine. However, biotechnological methods (fermentation) seem to be the most economical and practicable means of producing lysine. In the present study, production of lysine by Brevibacterium linens PTCC 1603 from whey and molasses medium, in the purpose of using agricultural by-products as low-cost sources for production of value-added products, was investigated. Whey medium was prepared by hydrolyzing of lactose with HCl and molasses medium was prepared by addition of some chemicals to it. The production of lysine was examined qualitatively and quantitatively using ascending thin layer chromatography (TLC) and spectrophotometry. Results showed that lysine concentration in both media was increased significantly by the time. The highest concentration of lysine produced from whey and molasses media were 11.8 and 10.5 g.L-1, respectively. Increasing lysine concentration resulted in pH increment in molasses medium, while the pH of whey medium was decreased. After 6 days of fermentation, the amount of lysine in whey medium was significantly higher than in molasses medium.

This study was conducted to determine lysine requirement of laying hen during peak egg production from 26 to 42 weeks. of age. The basal diet used was based on corn- corn gluten meal- soybean meal and contained 0.58% lysine. To the basal diet nine graded Levels of Lysine (0.04, 0.08, 0.12, 0.16, 0.2, 0.24, 0.28, 0.32, 0.36%) were added. The experimental diets were fed for 16 week. Each experimental diet was fed to 48 Laying hen in a randomized complete design with 4 replicate for each treatment. Broken-line and exponential models were used for estimation of lysine requirement. Dietary lysine levels had a significant effect on egg weight, egg mass output, feed intake(p< 0.01) and feed conversation ratio(p< 0.05) but hadnot significant effect on egg production .Based on egg mass output response and the fit of Broken-line and Exponential models the requirement for total lysine were estimated 645 and 710 mg per hen - day; respectively. Based on feed conversion efficiency Response and the fit of Broken-line and Exponential models the requirement for total lysine was estimated 750 and 810 mg per hen- day. In conclusion, the results of this experiment indicated that daily lysine requirement of laying hen during peak egg production was estimated 810 mg per her- day or 53 gram per kilograme of dietary crude protein.