Potentiality of Diethylamine as Agent of Deproteination and Deacetylation in the Extraction of Chitosan from Scylla serrata Shell

The potentiality of diethylamine as deproteination and deacetylation agent in the extraction of chitosan from Scylla serrata (giant mud crab) shell was investigated. The aim was to find an alternative agent to inorganic alkalis as possible replacement for use in the production of high quality chitosan with the right stability. Pretreatment of the shell was carried out and followed by demineralization using hydrochloric acid. Diethylamine was used for deproteination and deacetylation by modifying some published protocols. Moisture, ash, fat and protein contents of the extracts were determined using their respective standard methods. Fourier Transform Infrared (FTIR) technique was used for spectroscopic analysis. Scylla serrata shell was composed of 14.25% protein, 32.84% mineral (CaCO3), 31.52% chitin and 21.39% chitosan. Moisture, ash, fat and protein contents of chitin extracted from Scylla serrata shell were 2.35%, 3.03%, 1.79% and 3.85% respectively while those of chitosan were 1.65%, 3.84%, 0.53% and 2.80% respectively. Degree of deacetylation (DDA) and carbon to nitrogen ratio were 69.24% and 5.67 respectively. FTIR spectra of the extracted chitin and chitosan from Scylla serrata showed the presence of some active compounds of carbonyl, amide, amine and hydroxyl groups. However, CH3 waging along chain (952 cm-1), CO stretching at 1026 cm-1 and 1073 cm-1, and amide II band (1563 cm-1) were not found in the extracted chitin while HPO42- and amide III were also not found in the extracted chitosan. These moieties were present in the standard chitin and chitosan respectively. This study has shown that diethylamine (organic base) has great potential as agent of deproteination and deacetylation in the extraction of chitosan from Scylla serrata. Consequently, academic activity in the area of investigation of the stability of the extracted chitosan from Scylla serrata using diethylamine as deproteination and deacetylation agent is strongly recommended. Keywords: Diethylamine, deproteination, deacetylation, chitin and chitosan, Scylla serrata shell. DOI: 10.7176/CMR/12-7-07 Publication date:October 31st  2020

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Effect of alloy composition on the dendrite arm spacing of multicomponent aluminum alloys

Predictions of secondary dendrite arm spacing (SDAS) for multicomponent aluminum alloys using a dendrite ripening model are compared with experimental observations. For six of the seven alloys studied, the predicted SDAS was within 20 pct of the measured SDAS. It was found that the final SDAS was dependent upon both the solidification time and the solute profile of the solidifying alloys. It is interesting that while the solidification times and the solute segregation during solidification varied significantly over the range of alloys, these two factors largely canceled each other out so that the predicted SDAS did not vary much between the alloys. The experimental and modeling results show that elements causing high constitutional undercooling near the beginning of solidification, e.g., Ti, which reduces the grain size substantially, have little effect on the SDAS. Instead, it was found that elements that strongly partitioned toward the end of solidification were more effective at restricting SDAS coarsening