Optimization of the demineralization process for the extraction of chitin from Omani Portunidae segnis.

Chitin is an organic polymer and it is the most frequent marine natural polysaccharide after cellulose. The main natural sources of chitin are exoskeletons of insects, mollusks, the cell walls of certain fungi and crustaceans such as crabs, shrimps and lobsters. The waste of these marine exoskeletons are pollutant for the environment, but these waste raw materials could be useful for production of commercial products like chitin. Chitin is an important raw material used for water treatment, agricultural, biomedical, biotechnological purposes, food and paper industry and cosmetics. Based on the variety of importance, the present targets of this study are to optimize the demineralization process for the removal of calcium and phosphate contents from the waste of Portunidae segnis (P. segnis) by using acid at ambient temperature and to characterize the isolated demineralized sample as well as the percentage of remaining calcium and phosphorus contents by using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The prepared waste carbs coarse powder samples of P. segnis were demineralized with seven different concentrations of hydrochloric acid at ambient temperature for 1 h. All the demineralization samples by the different concentrations were analyzed by using sensitive ICP-OES. The results based on ICP-OES showed that among the seven different concentrations used in the demineralization process for the isolation of chitin, the best was 2 M of HCl concentration for the production of chitin. The results also showed that the optimized concentration 2 M HCl gave the minimum concentration of calcium and phosphorus compared to other concentrations applied in this experiment. In conclusion, the optimized concentration for demineralization process could be used commercially for the isolation or commercial production of chitin for agricultural, biomedical and biotechnological purposes.

Isolation and optimization of the method for industrial production of chitin and chitosan from Omani shrimp shell.

Chitosan is an organic compound widely used in biomedical and agricultural fields due to its medicinal values. Chitosan is the largest biopolymer after cellulose and it is used as a food supplement as well as a primary health care product. The focus of the present study is to optimize the method for isolation and characterization of chitosan from Omani shrimp shell. The chitosan was isolated chemically from shrimp waste through the chemical processes of demineralization, deproteinization, discoloration and deacetylation. Chitosan isolation was done using hydrochloric acid (HCl), sodium hydroxide (NaOH) and hydrogen peroxide (H2O2) at various concentrations and temperatures during the demineralization, the deproteinization, and the deacetylation processes. A total of twenty-seven samples were run in triplicate and used to isolate chitin from shrimp shell and then different methods of deacetylation were done to extract chitosan. The research was conducted by changing three variables such as the concentration of acid and base and temperature. The coarse powder shrimp waste samples were demineralized by varying the concentrations ranging from 3 to 9% of HCl and at the temperature range between 25 and 55 °C. The demineralized samples were treated with different concentrations of NaOH ranging from 20 to 60% and at the temperature range from 85 to 110 °C to deproteinize the samples. The optimal method for chitin isolation was selected by using FT-NIR spectroscopy. The optimal experimental conditions according to the present study were 3% HCl at 25 °C for an hour demineralization and 50% NaOH at 110 °C for 3 h deproteinization with a yield of 53.313%. Finally, the isolated chitin was decolorized by treatment with 30% H2O2 for 3 h then deacetylatised with 50% NaOH for 15 min. The weight loss was 0.29 gm/5 gm. In conclusion, shrimp waste could be a natural alternative source for the production of chitin. Furthermore, it could be used in medical, pharmaceutical, and biotechnology sectors.

Glucagon and Glucagon-like Peptide-1 Receptors: Promising Therapeutic Targets for an Effective Management of Diabetes Mellitus.

G-protein-coupled receptors (GPCRs) are membrane-bound proteins, which are responsible for the detection of extracellular stimuli and the origination of intracellular responses. Both glucagon and glucagon-like peptide-1 (GLP-1) receptors belong to G protein-coupled receptor (GPCR) superfamily. Along with insulin, glucagon and GLP-1 are critical hormones for maintaining normal serum glucose within the human body. Glucagon generally plays its role in the liver through cyclic adenosine monophosphate (cAMP), where it compensates for the action of insulin. GLP-1 is secreted by the L-cells of the small intestine to stimulate insulin secretion and inhibit glucagon action. Despite extensive research efforts and the multiple approaches adopted, the glycemic control in the case of type-2 diabetes mellitus remains a major challenge. Therefore, a deep understanding of the structure-function relationship of these receptors will have great implications for future therapies in order to maintain a normal glucose level for an extended period of time. The antagonists of glucagon receptors that can effectively block the hepatic glucose production, as a result of glucagon action, are highly desirable for the tuning of the hyperglycemic state in type 2 diabetes mellitus. In the same manner, GLP-1R agonists act as important treatment modalities, thanks to their multiple anti-diabetic actions to attain normal glucose levels. In this review article, the structural diversity of glucagon and GLP-1 receptors along with their signaling pathways, site-directed mutations and significance in drug discovery against type-2 diabetes are illustrated. Moreover, the promising non-peptide antagonists of glucagon receptor and agonists of GLP-1 receptor, for the management of diabetes are presented with elaboration on the structure-activity relationship (SAR).

Study of the effect of mixing approach on cross-linking efficiency of hyaluronic acid-based hydrogel cross-linked with 1,4-butanediol diglycidyl ether.

Regardless of various strategies reported for cross-linking hyaluronic acid (HA) with 1,4-butanediol diglycidyl ether (BDDE), seeking new strategies that enhance cross-linking efficiency with a low level of cross-linker is essential. In this work, we studied the influence of mixing approach on two cross-linked BDDE-HA hydrogels prepared by two different mixing approaches; the large-batch mixing approach in which the hydrogel quantities were all mixed as a single lump in one container (hydrogel 1), and the small-batches mixing approach in which the hydrogel quantities were divided into smaller batches, mixed separately at various HA/BDDE ratios then combined in one reaction mixture (hydrogel 2). The result showed that the cross-linking reaction was mixing process-dependent. Degradation tests proved that, in relation to hydrogel 1, hydrogel 2 was more stable, and exhibited a higher resistance towards hyaluronidase activity. The swelling ratio of hydrogel 1 was significantly higher than that of hydrogel 2 in distilled water; however, in phosphate buffer saline, both hydrogels showed no significant difference. SEM images demonstrated that hydrogel 2 composite showed a denser network structure and smaller pore-size than hydrogel 1. In comparison to native HA, the occurrence of chemical modification in the cross-linked hydrogels was confirmed by FTIR and NMR distinctive peaks. These peaks also provided evidence that hydrogel 2 exhibited a higher degree of modification than hydrogel 1. In conclusion, the small-batches mixing approach proved to be more effective than large-batch mixing in promoting HA-HA entanglement and increasing the probability of BDDE molecules for binding with HA chains.