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Cellulose – A Sustainable Material for Biomedical Applications
Published in Ashwani Kumar, Mangey Ram, Yogesh Kumar Singla, Advanced Materials for Biomechanical Applications, 2022
N. Vignesh, K. Chandraraj, S.P. Suriyaraj, R. Selvakumar
The synthesis of BC proceeds through a bottom-up approach wherein the glucose monomers taken up by the bacteria are assembled into cellulose through metabolic pathways inside the cell (Figure 4.1b). Initially, glucose is phosphorylated to glucose-6-phosphate by glucokinase. The isomerization of glucose-6-phosphate to glucose-1-phosphate is catalyzed by phosphoglucomutase. Further, glucose-1-phosphate is converted into uridine diphosphate glucose (UDPG) by UDPG pyrophosphorylase. The polymerization of glucose into cellulose is finally catalyzed by cellulose synthase through the formation of linear β-1,4-glucan chains [30]. The synthesized cellulose present in the form of protofibrils is secreted across the cell wall through transporters (Figure 4.1c). In the extracellular medium, the secreted protofibrils aggregate into microfibrils, which further organize into a desired nanostructure like a pellicle or mat depending on the culture condition [25].The production of BC is simple, as it requires optimum physical conditions like pH, temperature and aeration for the growth of the bacterial strain. Moreover, the secreted BC is treated with alkali to produce cellulose polymorph II for increasing the pore size, surface area and elasticity of the material [37]. Besides, the elevated porosity of BC facilitates its application as a precursor material for aerogel preparation (Figure 4.1d). To improve the properties of BC, in situ modification of its structure has been reported in many studies. Unlike an external chemical treatment, in situ modification refers to an alteration in the chemical composition of BC through the supplementation of additives in the growth medium. As a result, the desired components are incorporated into the structure of BC during microbial synthesis [38]. BC conjugates produced using additives such as polyvinyl alcohol, hydroxyapatite, chitosan, heparin and dextrin have been used for developing cardiovascular soft tissue, bone regeneration scaffold, antimicrobial membrane, anticoagulant wound dressing material and blood transfusion membrane respectively [29]. Eventhough BC is associated with intriguing properties and environmentally friendly production, the requirements of a large vessel, continuous aeration and longer process time are the major limitations hindering the commercial feasibility (Table 4.2).
A review of quorum sensing regulating heavy metal resistance in anammox process: Relations, mechanisms and prospects
Published in Critical Reviews in Environmental Science and Technology, 2023
Caiyan Qu, Fan Feng, Jia Tang, Xi Tang, Di Wu, Ruiyang Xiao, Xiaobo Min, Chong-Jian Tang
EPS constitute the first defense line against heavy metals into cells, which are produced through bacterial secretion, cell surface substance shedding, and cell lysis (Ni et al., 2009; Flemming & Wingender, 2010). Previous studies indicated that QS involved the regulation of EPS production in the anammox process (Tan et al., 2014; Tang et al., 2018b). Exogenous addition of 2 µM AHLs significantly increased the contents of extracellular proteins by 21–34% (p < 0.05) and polysaccharides by 6–17% (p < 0.05) in EPS of anammox consortia (Tang et al., 2018b). Further investigation found that AHL regulated the synthesis of amino acids (i.e., alanine, valine, glutamicacid, asparticacid and leucine) to produce proteins, and regulated the N-acetylmannosamine biosynthetic pathway and uridine diphosphate-Nacetylgalactosamine pathway to produce polysaccharides (Chavez-Dozal et al., 2015; Tang et al., 2018b). The increased EPS regulated by QS facilitated the biosorption for heavy metals. A single-metal biosorption study showed that the adsorption capabilities of EPS extracted from anammox consortia were up to 84.9, 52.8, 21.7 and 7.4 mg‧gTSEPS−1 for Pb(II), Cu(II), Ni(II) and Zn(II), respectively, demonstrating the strong biosorption ability of EPS to heavy metals (Pagliaccia et al., 2022).
Synergistic polymorphic interactions of phase II metabolizing genes and their association toward lung cancer susceptibility in North Indians
Published in International Journal of Environmental Health Research, 2022
Harleen Kaur Walia, Parul Sharma, Navneet Singh, Siddharth Sharma
The Phase I and Phase II enzymes, are of immense importance in the context of cancer as they are involved in the metabolism of steroid hormones, chemical carcinogens, and other environmental toxicants. In phase-I, reaction substrates are frequently reduced, oxidized, or hydroxylated, giving more polar metabolites; cytochrome P450 (CYP) enzymes are the primary mediators in this Phase.(Guengerich, 1999) Phase-II conjugation processes typically follow phase-I metabolism. The exogenous or endogenous chemicals, as well as their phase I metabolites, are conjugated to a more polar molecule during Phase II, resulting in inactive and water-soluble molecules easily eliminated by urine or bile.(Yang et al., 1994; Turesky, 2004) The sulfotransferases (SULTs), N-acetyltransferases (NATs), uridine diphosphate-glucuronosyltransferases (UGTs), Glutathione-S-transferases (GSTs), and methyltransferases are examples of conjugating enzymes. Although the combined Phase I and phase II metabolism is primarily the elimination and detoxification process, both phases bear the risk of producing toxic and highly reactive toxicants that can cause or promote significant health problems such as cancer (Windmill et al., 1997). As a result, the changes in metabolic enzyme activity can potentially increase exposure to carcinogenic chemicals and the risk of tumour formation.(Brockstedt et al., 2002; Justenhoven, 2012)
Role and application of quorum sensing in anaerobic ammonium oxidation (anammox) process: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Quan Zhang, Nian-Si Fan, Jin-Jin Fu, Bao-Cheng Huang, Ren-Cun Jin
In addition to improving the activity and growth rate of anammox bacteria, the QS-based technology also increases the secretion of EPS (Tang et al., 2015; Zhang et al., 2019), thus accelerating the aggregation of anammox bacteria in the initial startup stage. Furthermore, the regulation of the content of EPS by QS is realized by mediating the synthesis of uridine diphosphate-N-acetylgalactosamine (UDP-GlcNAc), suggesting that the regulation is indeed carried out at the metabolic level (Tang, Guo, Wu, et al., 2018). In brief, QS-based technology can be considered as an effective means for the fast startup of anammox process. More importantly, this regulation is at the metabolic level, which also provides a new perspective for the regulation of the anammox process.