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Mechanisms of phytoremediation and microbial remediation of heavy metals
Published in Rym Salah-Tazdaït, Djaber Tazdaït, Phyto and Microbial Remediation of Heavy Metals and Radionuclides in the Environment, 2022
Rym Salah-Tazdaït, Djaber Tazdaït
The following are the main reactive sites: Lipopolysaccharides (LPS) are chains of molecules evolving outside of cells. They are composed of a common lipid A on which is fixed a polysaccharide, which contains carboxyl groups and phosphomonoesters.Phospholipids are composed of hydrophobic chains attached to a glycerol unit on which is attached a hydrophilic group. On the latter, there are two reactive sites (amine and phosphodiester functions).The peptidoglycan (PG) network is a rigid structure composed of two sugar molecules (N-acetylglucosamine and N-acetylmuramic acid) linked to a short peptide (tetrapeptide to octapeptide). It contains three carboxyl functions and an amine(Cox, Smith, Warren, and Ferris 1999, 4514; Yee and Fein 2001, 2037). It should be noted that the constitutive wall differences between Gram-positive and Gram-negative cells seem to have a minor influence on the sorption capacities of metals (Yee and Fein 2001, 2037; Ngwenya, Sutherland, and Kennedy 2003, 537).
Characterization of Microorganisms by Pyrolysis-GC, Pyrolysis-GC/MS, and Pyrolysis-MS
Published in Karen D. Sam, Thomas P. Wampler, Analytical Pyrolysis Handbook, 2021
Stephen L. Morgan, Bruce E. Watt, Randolph C. Galipo
The cell envelope usually consists of a cell membrane, a cell wall, and an outer membrane [21,22]. Figure 9.1 shows schematic representations of the structure of Gram-positive and Gram-negative cell envelopes. The cell wall consists of the peptidoglycan (PG) layer and associated structures. PG is the only substance common to almost all bacteria (except Mycoplasma and Chlamydia) and absent in non-bacterial matter [23]. PG and its associated chemical components may account for up to 10–40% of the dry weight of the cell [5]. As seen in Figure 9.2, PG consists of a polysaccharide backbone that is a repeating polymer of N-acetylglucosamine and N-acetylmuramic acid. Attached covalently to the lactyl group of muramic acid are tetra- and pentapeptides (composed of repeating l- and d-amino acids) cross-linked by peptide bridges. The amino sugar muramic acid (3-O--carboxethyl-D-glucosamine) is a fairly definitive marker for bacteria. Other chemical markers in PG include d-alanine, d-glutamic acid, and diaminopimelic acid [24,25]. The d-amino acids are sometimes found in other bacterial components but are not synthesized by mammals. Different bacteria may vary in the sequence of the amino acids in the peptide sidechains and crossbridge.
Fabrication of Bionanocomposites from Chitosan
Published in Jissy Jacob, Sravanthi Loganathan, Sabu Thomas, Chitin- and Chitosan-Based Biocomposites for Food Packaging Applications, 2020
Anuradha Biswal, Sarat K. Swain
The biological/enzymatic deacetylation of chitin to chitosan is carried out in the presence of the enzyme chitin deacetylase. Chitin deacetylase belongs to the carbohydrate esterase family that is used in hydrolysis of the acetamido group of the N-acetylglucosamine units of chitin to produce acetic acid and glucosamine units. The deacetylase can also be extracted from organisms such as bacteria (V. cholera), insects (Helicoverpa armigera, Helicoverpa armigera, Drosophila melanogaster), and fungi (C. Lindemuthianum, F. Velutipes, M. Racemosus, A. Niger). In order to increase the efficiency of enzymatic deacetylation, such physical treatments as grinding, sonication, derivatization, and heating occur before deacetylation (Zhao, Park, and Muzzarelli 2010).
A review of microalgal cell wall composition and degradation to enhance the recovery of biomolecules for biofuel production
Published in Biofuels, 2023
Syafiqah Md Nadzir, Norjan Yusof, Norazela Nordin, Azlan Kamari, Mohd Zulkhairi Mohd Yusoff
Most microalgal species that have been studied as potential feedstock for biofuel production have a Type 2 cell surface [17–19]. Compared to the other forms of cell surface, the Type 2 extracellular material of some microalgae and cyanobacteria is the most complicated (Figure 1). Depending on the type of species, it can appear as a cell wall, mucilage sheath, scales, frustule, lorica, or skeleton [20,21]. In both prokaryotic and eukaryotic algae, the cell wall is a semi-permeable, rigid, and frequently multilayered protective covering. The peptidoglycan-based cell wall of cyanobacteria resembles that of Gram-negative bacteria, in which the cell wall is placed exterior to the cell membrane. The peptidoglycan consists of two sugar derivatives, N-acetylglucosamine and N-acetylmuramic acid, linked by β-1,4-glycosidic bonds [22]. The three most important functions of peptidoglycan are maintaining osmotic pressure between the cell and its external environment, preserving cell shape, and providing rigidity.
Dense lamellar scaffold, biomimetically inspired, for reverse cardiac remodeling: Effect of proanthocyanidins and glutaraldehyde
Published in Journal of Dispersion Science and Technology, 2021
Thais Alves, Juliana Ferreira Souza, Venancio Alves Amaral, Alessandra Candida Rios, Tais Costa, Kessi Crescencio, Fernando Batain, Denise Grotto, Renata Lima, Lindemberg Silveira Filho, Jose Oliveira Junior, Patricia Severino, Norberto Aranha, Marco Chaud
Proteins and polysaccharides are considered promising natural molecules for the design of 3D scaffolds with biomimetic characteristics of original tissue. Type I collagen makes up about 80% of the collagen matrix in cardiac tissue, making this biopolymer an attractive for the manufacture of scaffolds for cardiac tissue. Collagen in combination with other biomaterials such as chitosan showed an increase in the elastic modulus, which makes it more suitable for the stabilization of the ventricular wall. Chitosan (Qt) is a natural polymer composed of glucosamine and N-acetylglucosamine. A chitosan hydrogel has been designed, which improved the survival of embryonic stem cells and the differentiation of cardiomyocytes in a rat infarction model.[9–11]
HEMA and alginate-based chondrogenic semi-interpenetrated hydrogels: synthesis and biological characterization
Published in Journal of Biomaterials Science, Polymer Edition, 2020
María Luz Torres, Tamara Gisela Oberti, Juan Manuel Fernández
The extracellular matrix of cartilage contains hyaluronan, which has an important role in chondrocyte proliferation and differentiation [8]; thus, hyaluronan-like material should be studied for cartilage tissue engineering. Hyaluronan is a disaccharide composed of N-acetylglucosamine and D-glucuronic acid. Alginate is a natural polymer composed of L-glucuronic acid and D-mannuronic acid, the latter presenting a high homology with D-glucuronic acid of hyaluronan. Alginate has the ability to form hydrogels due to physical crosslinking with divalent metals. These hydrogels have low toxicity/inflammatory response and good biocompatibility; however, they are unstable over time [3]. Poly(2-hydroxyethyl methacrylate) (pHEMA) is a hydrophilic polymer highly studied in the formulation of biomaterials (among them, hydrogels); however, materials based on this polymer usually have a low capacity for cell adhesion and biocompatibility [9].