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Degradation Pathways of Various Plastics
Published in Hyunjung Kim, Microplastics, 2023
Hyunjung Kim, Sadia Ilyas, Gukhwa Hwang
Hydrolyzable polymers such as PET, PA, and polyurethane are usually more susceptible to biodegradation due to the presence of existing biodegradation pathways such as extracellular hydrolases involved in the degradation of cellulose and proteins (Chen et al., 2019). PETase, an enzyme capable of hydrolyzing PET initially identified in Ideonella sakaiensis was found to be ubiquitous in the environment (Danso et al., 2018). Enzymes such as cutinase, lipase, serine esterase, and nitro-benzyl-esterase have also been found to be capable of hydrolyzing PET, whereas protease, cutinase, amidase, and hydrolase are involved in the hydrolysis of PA (Guebitz and Cavaco-Paulo, 2008). Meanwhile, esterase and polyester hydrolase from bacteria and fungi might be responsible for polyurethane hydrolysis (Akutsu et al., 1998; Russell et al., 2011). In addition to hydrolysis, enzymatic oxidation may also contribute to the oxidative degradation of hydrolyzable polymers (Magnin et al., 2020).). Non-hydrolyzable polymers can be oxidized by O2 with the catalysis of those enzymes, resulting in the formation of degradation products of low molecular weight.
Waterborne Polyurethanes for Biodegradable Coatings
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Sukanya Pradhan, Smita Mohanty, Sanjay Kumar Nayak
Esterases are the well-known enzymes for the degradation of soft segments of PU through hydrolytic cleavage, thereby generating carboxylic and alcohol groups as end products. The other two enzymes are proteases and amidases, which are responsible for the fragmentation of peptide and amide bonds as well as the urethane linkages present in PU. The simultaneous action of enzymes amidases and esterase on the degradation behavior of PU has been well studied and showed its improved efficiency compared to enzymes when used individually. During the enzymatic action, the esterase hydrolyzes the ester linkages, and the resultant low molecular weight intermediates being susceptible to amidase; hence, the hydrolysis of urethane bonds occurs. Further, reports also reveal the hydrolytic enzymatic activity of an amidase from Nocardia farcinica responsible for the degradation of polyester-based PU containing polyamides (PAs) and PA-related oligomeric model substrates. Furthermore, urease is also capable of microbial degradation of poly-urea-urethane polymers into amines and carbon dioxide. However, very little supporting literature is available to date as the disintegration of urea bonds is a very tough task compared to the ester bonds. The prospects in this area, therefore, deal with the exploration of screening of enzymes with “polyurethanase” activity.
Smart Nanoparticles in Drug/Gene Delivery
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Mahdi Karimi, Michael R. Hamblin
Polymer hydrogels can be directly degraded by enzymes such as elastase and metalloproteinases [305–308]. Enzymes can not only destroy the polymer hydrogel structure but also control the morphology of the hydrogel particles as well. Using enzymes such as trypsin, thermolysin, and elastase the degree of swelling in polymers can be altered leading to drug release [300–303]. Klinger et al. designed an enzyme-degradable hydrogel by cross-linking poly(PAAm) with dextran-methacrylate (Dex-MA) that was partially biodegradable by enzymatic cleavage of the methacryl-functionalized polysaccharide chains [309]. 1,4-Hydroxymandelic acid was used as a framework to attach an enzyme-cleavable group such as phenylacetic acid which was cleaved by bacterial penicillin G amidase. A TAT peptide acted as a protein-transduction domain, and nalidixic acid was the antibacterial cargo. The enzyme-activated system exhibited a minimum inhibitory concentration (MIC) value against Escherichia coli about 70 times lower (1.9 µM) than that of free nalidixic acid (138 µM) [310–313].
Proteomic analysis of secretomes from Bacillus sp. AR03: characterization of enzymatic cocktails active on complex carbohydrates for xylooligosaccharides production
Published in Preparative Biochemistry & Biotechnology, 2021
Johan S. Hero, José H. Pisa, Enzo E. Raimondo, M. Alejandra Martínez
Differential proteome from condition 2 presented unique proteins related to cell cycle control and mitosis (D) (P07788, a putative spore coat protein), lipid transport and metabolism (I) (O34421, a putative acyl-CoA dehydrogenase), replication, recombination, and repair of DNA (L) (P54521, exodeoxyribonuclease), and cell wall/membrane/envelope biogenesis (M) (P23261 spore coat protein; Q06320 sporulation-specific N-acetylmuramoyl-L-alanine amidase) (Fig. 3, Supplementary Table 1). In addition, 13 proteins not classified into any COG category were detected in the differential proteome obtained from the medium with CMC (Supplementary Material 3). Those mainly encompass proteins associated with sporulation and protein degradation processes (Supplementary Table 1). The up-regulation of these proteins might be evidence of a stress state of Bacillus sp. AR03 in the medium with CMC at 72 hr of growth, and would be associated with the lower values of OD and enzymatic activities observed in this condition (Fig. 1). Previously, other researchers identified these sporulation proteins in Bacillus species through proteomic studies and described their importance as indicators of cellular stress status.[35,36] Additionally, the role of the transcriptional regulation of the gene coding for N-acetylmuramoyl-L-alanine amidase in the mother cell lysis during sporulation of B. thuringiensis was reported by Yang et al.[37]
A review on viscosity retention of PAM solution for polymer flooding technology
Published in Petroleum Science and Technology, 2022
Juan Du, Chunhong Lv, Xitang Lan, Jifeng Song, Pingli Liu, Xiang Chen, Qiang Wang, Jinming Liu, Guixian Guo
The essence of biodegradation is that microorganisms grow with the organic matter in wastewater as raw materials, and use the mass reproduction and self-metabolism of microorganisms to decompose the high molecular organic matter contained in wastewater into small molecular organic matter fragments and produce CO2 and H2O (Sang et al. 2015; Song et al. 2019). The biodegradation of PAM includes amino hydrolysis and carbon chain breaking (Song et al. 2020; Zhao et al. 2019). Amino hydrolysis is the deamination reaction of PAM under the catalysis of amidase. The reaction products are ammonia and polyacrylate (Figure 6). The liberated ammonia can provide nitrogen source for microorganisms (Hu et al. 2018a; Li et al. 2016; Nyyssölä and Ahlgren 2019).
Physiology and selected genes expression under cadmium stress in Arundo donax L
Published in International Journal of Phytoremediation, 2018
Shahida Shaheen, Rafiq Ahmad, Qaisar Mahmood, Hussani Mubarak, Nosheen Mirza, Malik Tahir Hayat
Arundo donax plants showed differential expression of metal transporter and stress responsive genes like carotenoid hydroxilase, amidase, glutathione reductase, transcription factor, natural-resistance–associated macrophage protein and Yellow stripe-like genes under Cd stress. Already published results of RT-PCR analysis showed the higher expression of NtNRAMP1 gene in leaf and root tissue of Nicotiana tabacum under cadmium and zinc contamination and concluded that these genes were supposed to be involved in Cd and Zn sequestration (Milner and Kochian 2008). NRAMP3 and NRAMP4 genes were found to be responsible for Cd2+ efflux from the vacuole (Verbruggen et al.2009). In current study, we observed slightly higher expression of NRAMP gene under Cd stress in A. donax. The expression pattern of metal transporter gene family in Thlaspi caerulescens under Cd stress also revealed that TcNRAMP3 and TcNRAMP4 gene expression enhanced metal tolerance (Oomen et al.2009). Previously, the expression level of the transcription factor (bHLH) of A. donax was analyzed under CrVI stress (Shaheen et al.2017). Currently, differential expression against various concentration of Cd toxicity was investigated and medium Cd stress induced bHLH expression at high Cd stress. Published studies revealed that the antioxidant responsive enzymes and transcription factors (bHLH) by the AtbHLH112 gene expression assisted the Arabidopsis thaliana to cope abiotic stress (Liu et al.2015). The carotene hydroxylase (BCH2) gene expression was studied in Oncidium during pigment development of flowers where higher expression was observed (Wang et al.2017). The same gene has also been previously expressed in A. donax under Cr stress (Shaheen et al.2017). The expression of this gene during current investigation under Cd stress is suggestive of its role in preventing yellowing of leaves upon metal exposure. Many studies reported the expression of Yellow Stripe-Like (YSL) genes in metal transportation and hyper-accumulation; Yellow Stripe-Like2 (YSL2) was found to be involved in transportation of Iron Fe (III) and Copper in Arabidopsis (DiDonato et al.2004). The expression of YSL genes was confirmed in barley, Brachypodium, foxtail millet, maize and rice for uptake, transportation and accumulation of Fe and Zn (Mallikarjuna et al.2016). The expression of Yellow Stripe-Like (YSL) genes has also been confirmed for Cd hyperaccumulator Solanum nigrum (Feng et al.2017). Amidase enzyme has been tested for the removal and degradation of many industrial and agricultural wastes (Karigar and Rao 2011). The current study is the first report on expression of amidase responsive gene in A. donax under Cd stress.