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Jaffur BN, Kumar G, Jeetah P, Ramakrishna S, Bhatia SK. Current advances and emerging trends in sustainable polyhydroxyalkanoate modification from organic waste streams for material applications. Int J Biol Macromol 2023; 253:126781. [PMID: 37696371 DOI: 10.1016/j.ijbiomac.2023.126781] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 08/29/2023] [Accepted: 09/05/2023] [Indexed: 09/13/2023]
Abstract
The current processes for producing polyhydroxyalkanoates (PHAs) are costly, owing to the high cost of cultivation feedstocks, and the need to sterilise the growth medium, which is energy-intensive. PHA has been identified as a promising biomaterial with a wide range of potential applications and its functionalization from waste streams has made significant advances recently, which can help foster the growth of a circular economy and waste reduction. Recent developments and novel approaches in the functionalization of PHAs derived from various waste streams offer opportunities for addressing these issues. This study focuses on the development of sustainable, efficient, and cutting-edge methods, such as advanced bioprocess engineering, novel catalysts, and advances in materials science. Chemical techniques, such as epoxidation, oxidation, and esterification, have been employed for PHA functionalization, while enzymatic and microbial methods have indicated promise. PHB/polylactic acid blends with cellulose fibers showed improved tensile strength by 24.45-32.08 % and decreased water vapor and oxygen transmission rates while PHB/Polycaprolactone blends with a 1:1 ratio demonstrated an elongation at break four to six times higher than pure PHB, without altering tensile strength or elastic modulus. Moreover, PHB films blended with both polyethylene glycol and esterified sodium alginate showed improvements in crystallinity and decreased hydrophobicity.
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Affiliation(s)
- Bibi Nausheen Jaffur
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Mauritius, Réduit 80837, Mauritius.
| | - Gopalakrishnan Kumar
- Institute of Chemistry, Bioscience and Environmental, Engineering, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway; School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, South Korea
| | - Pratima Jeetah
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Mauritius, Réduit 80837, Mauritius
| | - Seeram Ramakrishna
- Department of Mechanical Engineering, College of Design and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
| | - Shashi Kant Bhatia
- Department of Biological Engineering, Konkuk University, Seoul 05029, South Korea
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2
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Morya R, Andrianantenaina FH, Pandey AK, Yoon YH, Kim SH. Polyhydroxyalkanoate production from rice straw hydrolysate: Insights into feast-famine dynamics and microbial community shifts. CHEMOSPHERE 2023; 341:139967. [PMID: 37634586 DOI: 10.1016/j.chemosphere.2023.139967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/03/2023] [Accepted: 08/24/2023] [Indexed: 08/29/2023]
Abstract
Activated sludge contains a versatile microbiome capable of converting wastes into valuable chemicals like polyhydroxyalkanoates (PHA). This study investigated the influence of repeated feast and famine phases on PHA production as well as the corresponding microbial population dynamics using waste activated sludge (WAS) as inoculum. Hydrolysate derived from rice straw was employed as a substrate for PHA production. The 16sRNA analysis results revealed that Corynebacteriaceae (40%), Bacillaceae (23%), and Pseudomonas (5%) were the primary contributors to PHA synthesis. Notably, Bacillaceae and Pseudomonas thrived in all the feast and famine phases. The achieved PHA concentration was 3.5 ± 0.2 g/L, and its structure and composition were assessed using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). The analysis revealed that the PHA consists of a copolymer of hydroxybutyrate (HB) and hydroxyvalerate (HV), specifically identified as Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV).
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Affiliation(s)
- Raj Morya
- Department of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | | | - Ashutosh Kumar Pandey
- Department of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | - Young Hye Yoon
- Department of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
| | - Sang-Hyoun Kim
- Department of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.
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3
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Kee PE, Chiang YC, Ng HS, Lan JCW. Expression of His-tagged NADPH-dependent acetoacetyl-CoA reductase in recombinant Escherichia coli BL-21(DE3). J Biosci Bioeng 2023; 136:312-319. [PMID: 37500302 DOI: 10.1016/j.jbiosc.2023.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 06/14/2023] [Accepted: 07/01/2023] [Indexed: 07/29/2023]
Abstract
Poly-3-hydroxybutyrate (P(3HB)), a member of the polyhydroxyalkanoate (PHA) family, is a biodegradable polyester with diverse industrial applications. NADPH-dependent acetoacetyl-CoA reductase (phaB) is the enzyme which plays an essential role in P(3HB) synthesis by catalyzing the conversion of the intermediates. The expression of phaB enzyme using the recombinant Escherichia coli BL-21(DE3) and the purification of the synthesized enzyme were studied. The pET-B3 plasmid harbouring the phaB gene derived from Ralstonia eutropha H16, was driven by the lac promoter in E. coli BL-21(DE3). The enzyme was expressed with different induction time, temperatures and cell age. Results showed that the cell age of 4 h, induction time of 12 h at 37°C were identified as the optimal conditions for the enzyme reductase expression. A specific activity of 0.151 U mg-1 protein and total protein concentration of 0.518 mg mg-1 of dry cell weight (DCW) were attained. Affinity chromatography was performed to purify the His-tagged phaB enzyme, in which enhanced the specific activity (14.44 U mg-1) and purification fold (38-fold), despite relative low yield (44.6%) of the enzyme was obtained. The purified phaB showed an optimal enzyme activity at 30°C and pH 8.0. The findings provide an alternative for the synthesis of the reductase enzyme which can be used in the industrial-scale production of the biodegradable polymers.
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Affiliation(s)
- Phei Er Kee
- Centre for Research and Graduate Studies, University of Cyberjaya, Persiaran Bestari, Cyberjaya, 63000 Selangor, Malaysia
| | - Yi-Cheng Chiang
- Biorefinery and Bioprocess Engineering Laboratory, Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li 32003, Taiwan
| | - Hui Suan Ng
- Centre for Research and Graduate Studies, University of Cyberjaya, Persiaran Bestari, Cyberjaya, 63000 Selangor, Malaysia
| | - John Chi-Wei Lan
- Biorefinery and Bioprocess Engineering Laboratory, Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li 32003, Taiwan; Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Chung-Li 32003, Taiwan.
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4
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Pathak VM. Exploitation of bacterial strains for microplastics (LDPE) biodegradation. CHEMOSPHERE 2023; 316:137845. [PMID: 36649894 DOI: 10.1016/j.chemosphere.2023.137845] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 12/09/2022] [Accepted: 01/10/2023] [Indexed: 06/17/2023]
Abstract
Plastic waste (microplastics) is one of the primary sources of environmental pollutants, serving as a reservoir for them. In this study, previously isolated and screened polymer-degrading bacteria (B. subtilis V8, P. aminophilusB1 4-, P. putida C 2 5, P. aeruginosa V1, and A. calcoaceticus V4) were utilised to examine the biodegradation of LDPE (low-density polyethylene) microplastics. Response surface methodology (RSM) was used to optimize the physicochemical growth parameters (pH, temperature, and ammonium sulphate concentration). By using the polyphasic approach, including CO2 estimation, weight loss analysis, scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, and electrical conductivities examine the plastic biodegradability. After four months, all biodegradable plastic samples were evaluated. When compared to the other tested cultures, P. aeruginosa V1 showed the most significant degradation (CO2evolution of 8.86 g.l-l and percentage weight loss of 18.21 %) with increased electrical conductivity, followed by B. subtilis V8 (CO2 evolution of 8.10 g.l-l and percentage weight loss of 16.12 %), A. calcoaceticus V4 (CO2 evolution of 7.21 g.l-l and percentage weight loss of 15.44 %), P. putida C 2-5 (CO2 evolution of 5.76 g.l-l and percentage weight loss of 13.30 %), and P. aminophilus B1 4- (CO2 evolution of 5.62 g.l-l and percentage weight loss of 11.72 %). The deteriorated materials' exterior modifications (surface alteration) were also examined using SEM analysis, and the chemical bonding alterations (bond vibration-bending) were determined using FT-IR spectroscopy.
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Affiliation(s)
- Vinay Mohan Pathak
- Department of Botany & Microbiology, Gurukul Kangri (Deemed to be University), Haridwar, 249404, India; University of Delhi, South Campus, New Delhi, 110021, India.
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5
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Mohanan N, Wong MCH, Budisa N, Levin DB. Polymer-Degrading Enzymes of Pseudomonas chloroaphis PA23 Display Broad Substrate Preferences. Int J Mol Sci 2023; 24:ijms24054501. [PMID: 36901931 PMCID: PMC10003648 DOI: 10.3390/ijms24054501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 01/27/2023] [Accepted: 02/14/2023] [Indexed: 03/02/2023] Open
Abstract
Although many bacterial lipases and PHA depolymerases have been identified, cloned, and characterized, there is very little information on the potential application of lipases and PHA depolymerases, especially intracellular enzymes, for the degradation of polyester polymers/plastics. We identified genes encoding an intracellular lipase (LIP3), an extracellular lipase (LIP4), and an intracellular PHA depolymerase (PhaZ) in the genome of the bacterium Pseudomonas chlororaphis PA23. We cloned these genes into Escherichia coli and then expressed, purified, and characterized the biochemistry and substrate preferences of the enzymes they encode. Our data suggest that the LIP3, LIP4, and PhaZ enzymes differ significantly in their biochemical and biophysical properties, structural-folding characteristics, and the absence or presence of a lid domain. Despite their different properties, the enzymes exhibited broad substrate specificity and were able to hydrolyze both short- and medium-chain length polyhydroxyalkanoates (PHAs), para-nitrophenyl (pNP) alkanoates, and polylactic acid (PLA). Gel Permeation Chromatography (GPC) analyses of the polymers treated with LIP3, LIP4, and PhaZ revealed significant degradation of both the biodegradable as well as the synthetic polymers poly(ε-caprolactone) (PCL) and polyethylene succinate (PES).
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Affiliation(s)
- Nisha Mohanan
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada
| | - Michael C.-H. Wong
- Department of Chemistry, University of Manitoba, 144 Dysart Rd., Winnipeg, MB R3T 2N2, Canada
| | - Nediljko Budisa
- Department of Chemistry, University of Manitoba, 144 Dysart Rd., Winnipeg, MB R3T 2N2, Canada
- Biocatalysis Group, Technical University of Berlin, Müller-Breslau-Str. 10, D-10623 Berlin, Germany
- Correspondence: or (N.B.); (D.B.L.); Tel.: +1-204-474-7429
| | - David B. Levin
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada
- Correspondence: or (N.B.); (D.B.L.); Tel.: +1-204-474-7429
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6
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Khare R, Khare S. Polymer and its effect on environment. J INDIAN CHEM SOC 2023. [DOI: 10.1016/j.jics.2022.100821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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7
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Bher A, Mayekar PC, Auras RA, Schvezov CE. Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments. Int J Mol Sci 2022; 23:12165. [PMID: 36293023 PMCID: PMC9603655 DOI: 10.3390/ijms232012165] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 10/03/2022] [Accepted: 10/07/2022] [Indexed: 08/29/2023] Open
Abstract
Finding alternatives to diminish plastic pollution has become one of the main challenges of modern life. A few alternatives have gained potential for a shift toward a more circular and sustainable relationship with plastics. Biodegradable polymers derived from bio- and fossil-based sources have emerged as one feasible alternative to overcome inconveniences associated with the use and disposal of non-biodegradable polymers. The biodegradation process depends on the environment's factors, microorganisms and associated enzymes, and the polymer properties, resulting in a plethora of parameters that create a complex process whereby biodegradation times and rates can vary immensely. This review aims to provide a background and a comprehensive, systematic, and critical overview of this complex process with a special focus on the mesophilic range. Activity toward depolymerization by extracellular enzymes, biofilm effect on the dynamic of the degradation process, CO2 evolution evaluating the extent of biodegradation, and metabolic pathways are discussed. Remarks and perspectives for potential future research are provided with a focus on the current knowledge gaps if the goal is to minimize the persistence of plastics across environments. Innovative approaches such as the addition of specific compounds to trigger depolymerization under particular conditions, biostimulation, bioaugmentation, and the addition of natural and/or modified enzymes are state-of-the-art methods that need faster development. Furthermore, methods must be connected to standards and techniques that fully track the biodegradation process. More transdisciplinary research within areas of polymer chemistry/processing and microbiology/biochemistry is needed.
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Affiliation(s)
- Anibal Bher
- School of Packaging, Michigan State University, East Lansing, MI 48824, USA
- Instituto de Materiales de Misiones, CONICET-UNaM, Posadas 3300, Misiones, Argentina
| | - Pooja C. Mayekar
- School of Packaging, Michigan State University, East Lansing, MI 48824, USA
| | - Rafael A. Auras
- School of Packaging, Michigan State University, East Lansing, MI 48824, USA
| | - Carlos E. Schvezov
- Instituto de Materiales de Misiones, CONICET-UNaM, Posadas 3300, Misiones, Argentina
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Mohanan N, Wong CH, Budisa N, Levin DB. Characterization of Polymer Degrading Lipases, LIP1 and LIP2 From Pseudomonas chlororaphis PA23. Front Bioeng Biotechnol 2022; 10:854298. [PMID: 35519608 PMCID: PMC9065602 DOI: 10.3389/fbioe.2022.854298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 03/22/2022] [Indexed: 11/16/2022] Open
Abstract
The outstanding metabolic and bioprotective properties of the bacterial genus Pseudomonas make these species a potentially interesting source for the search of hydrolytic activities that could be useful for the degradation of plastics. We identified two genes encoding the intracellular lipases LIP1 and LIP2 of the biocontrol bacterium Pseudomonas chlororaphis PA23 and subsequently performed cloning and expression in Escherichia coli. The lip1 gene has an open reading frame of 828 bp and encodes a protein of 29.7 kDa whereas the lip2 consists of 834 bp and has a protein of 30.2 kDa. Although secondary structure analyses of LIP1 and LIP2 indicate a dominant α/β-hydrolase-fold, the two proteins differ widely in their amino acid sequences (15.39% identity), substrate specificities, and hydrolysis rates. Homology modeling indicates the catalytic serine in both enzymes located in a GXSXG sequence motif (lipase box). However, LIP1 has a catalytic triad of Ser152-His253-Glu221 with a GGX-type oxyanion pocket, whereas LIP2 has Ser138-His249-Asp221 in its active site and a GX-type of oxyanion hole residues. However, LIP1 has a catalytic triad of Ser152-His253-Glu221 with an oxyanion pocket of GGX-type, whereas LIP2 has Ser138-His249-Asp221 in its active site and a GX-type of oxyanion hole residues. Our three-dimensional models of LIP1 and LIP2 complexed with a 3-hydroxyoctanoate dimer revealed the core α/β hydrolase-type domain with an exposed substrate binding pocket in LIP1 and an active-site capped with a closing lid domain in LIP2. The recombinant LIP1 was optimally active at 45°C and pH 9.0, and the activity improved in the presence of Ca2+. LIP2 exhibited maximum activity at 40°C and pH 8.0, and was unaffected by Ca2+. Despite different properties, the enzymes exhibited broadsubstrate specificity and were able to hydrolyze short chain length and medium chain length polyhydroxyalkanoates (PHAs), polylactic acid (PLA), and para-nitrophenyl (pNP) alkanoates. Gel Permeation Chromatography (GPC) analysis showed a decrease in the molecular weight of the polymers after incubation with LIP1 and LIP2. The enzymes also manifested some polymer-degrading activity on petroleum-based polymers such as poly(ε-caprolactone) (PCL) and polyethylene succinate (PES), suggesting that these enzymes could be useful for biodegradation of synthetic polyester plastics. The study will be the first report of the complete characterization of intracellular lipases from bacterial and/or Pseudomonas species. The lipases, LIP1 and LIP2 are different from other bacterial lipases/esterases in having broad substrate specificity for polyesters.
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Affiliation(s)
- Nisha Mohanan
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, Canada
| | - Chun Hin Wong
- Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada
| | - Nediljko Budisa
- Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada
| | - David B. Levin
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, Canada
- *Correspondence: David B. Levin,
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Amir M, Bano N, Baker A, Zia Q, Banawas S, Zaheer MR, Shariq M, Nawaz MS, Khan MF, Azad ZRAA, Gupta A, Iqbal D. Isolation and optimization of extracellular PHB depolymerase producer Aeromonas caviae Kuk1-(34) for sustainable solid waste management of biodegradable polymers. PLoS One 2022; 17:e0264207. [PMID: 35421107 PMCID: PMC9009665 DOI: 10.1371/journal.pone.0264207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Accepted: 02/05/2022] [Indexed: 11/19/2022] Open
Abstract
Bioplastics, synthesized by several microbes, accumulates inside cells under stress conditions as a storage material. Several microbial enzymes play a crucial role in their degradation. This research was carried to test the biodegradability of poly-β-hydroxybutyrate (PHB) utilizing PHB depolymerase, produced by bacteria isolated from sewage waste soil samples. Potent PHB degrader was screened based on the highest zone of hydrolysis followed by PHB depolymerase activity. Soil burial method was employed to check their degradation ability at different incubation periods of 15, 30, and 45 days at 37±2°C, pH 7.0 at 60% moisture with 1% microbial inoculum of Aeromonas caviae Kuk1-(34) (MN414252). Without optimized conditions, 85.76% of the total weight of the PHB film was degraded after 45 days. This degradation was confirmed with Fourier-transform infrared spectroscopy (FTIR) and Scanning electron microscope (SEM) analysis. The presence of bacterial colonies on the surface of the degraded film, along with crest, holes, surface erosion, and roughness, were visible. Media optimization was carried out in statistical mode using Plackett Burman (PB) and Central Composite Design (CCD) of Response Surface Methodology (RSM) by considering ten different factors. Analysis of Variance (ANOVA), Pareto chart, response surface plots, and F-value of 3.82 implies that the above statistical model was significant. The best production of PHB depolymerase enzyme (14.98 U/mL) was observed when strain Kuk1-(34) was grown in a media containing 0.1% PHB, K2HPO4 (1.6 gm/L) at 27 ℃ for seven days. Exploiting these statistically optimized conditions, the culture was found to be a suitable candidate for the management of solid waste, where 94.4% of the total weight of the PHB film was degraded after 45 days of incubation.
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Affiliation(s)
- Mohammad Amir
- Protein Research Laboratory, Department of Bioengineering, Integral University, Lucknow, India
| | - Naushin Bano
- Protein Research Laboratory, Department of Bioengineering, Integral University, Lucknow, India
| | - Abu Baker
- Protein Research Laboratory, Department of Bioengineering, Integral University, Lucknow, India
| | - Qamar Zia
- Health and Basic Science Research Centre, Majmaah University, Majmaah, Saudi Arabia
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah, Saudi Arabia
| | - Saeed Banawas
- Health and Basic Science Research Centre, Majmaah University, Majmaah, Saudi Arabia
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah, Saudi Arabia
- Department of Biomedical Sciences, Oregon State University, Corvallis, Oregon, United States of America
| | - Mohd Rehan Zaheer
- Department of Science, Gagan College of Management and Technology, Aligarh, India
| | - Mohammad Shariq
- Department of Physics, Faculty of Science, Jazan University, Jazan, Saudi Arabia
| | - Md Sarfaraz Nawaz
- Department of Chemistry, Faculty of Science, Jazan University, Jazan, Saudi Arabia
| | - Mohd Farhan Khan
- Department of Science, Gagan College of Management and Technology, Aligarh, India
- Nano Solver Lab, Department of Mechanical Engineering, Z. H. College of Engineering & Technology, Aligarh Muslim University, Aligarh, India
| | - Z R Azaz Ahmad Azad
- Department of Post-Harvest Engineering and Technology, Aligarh Muslim University, Aligarh, India
| | - Anamika Gupta
- Department of Chemistry, Aligarh Muslim University, Aligarh, India
| | - Danish Iqbal
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah, Saudi Arabia
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Kotova IB, Taktarova YV, Tsavkelova EA, Egorova MA, Bubnov IA, Malakhova DV, Shirinkina LI, Sokolova TG, Bonch-Osmolovskaya EA. Microbial Degradation of Plastics and Approaches to Make it More Efficient. Microbiology (Reading) 2021. [DOI: 10.1134/s0026261721060084] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Abstract—
The growing worldwide production of synthetic plastics leads to increased amounts of plastic pollution. Even though microbial degradation of plastics is known to be a very slow process, this capacity has been found in many bacteria, including invertebrate symbionts, and microscopic fungi. Research in this field has been mostly focused on microbial degradation of polyethylene, polystyrene, and polyethylene terephthalate (PET). Quite an arsenal of different methods is available today for detecting processes of plastic degradation and measuring their rates. Given the lack of generally accepted protocols, it is difficult to compare results presented by different authors. PET degradation by recombinant hydrolases from thermophilic actinobacteria happens to be the most efficient among the currently known plastic degradation processes. Various approaches to accelerating microbial plastic degradation are also discussed.
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Akan OD, Udofia GE, Okeke ES, Mgbechidinma CL, Okoye CO, Zoclanclounon YAB, Atakpa EO, Adebanjo OO. Plastic waste: Status, degradation and microbial management options for Africa. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 292:112758. [PMID: 34030015 DOI: 10.1016/j.jenvman.2021.112758] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 04/25/2021] [Accepted: 05/03/2021] [Indexed: 06/12/2023]
Abstract
This paper presents a review of synthetic polymer (notably plastic) wastes profiles in Africa, their current management status, and better options. Data revealed that of the approximated 86.14 million metric tonnes and 31.5 million metric tonnes of primary polymers and plastics, respectively, and an estimated 230 million metric tonnes of plastic components imported between 1990 and 2017, about 17 million metric tonnes are mismanaged. Leading African nations on the plastic wastes generator table in increasing order are Tunisia (6.9%), Morocco (9.6%), Algeria (11.2%), South Africa (11.6%), Nigeria (16.9%), and the chief is Egypt (18.4%). The volume of plastic wastes generated in Africa directly correlates with her increasing population status, however, the current treatment options have major drawbacks (high energy and technological input, high demand for space, and creation of obnoxious by-products). Ineffective regulations, poor monitoring, and slow adoption of veritable practices by governments are responsible for the steady increase in plastic volume in the African landscapes and environments. In Nigeria, only about 9% and 12% of the total generated wastes are recycled and incinerated. The remainder bulk is either discarded into waste dumps (and a few available landfills) or natural environments. There is a paucity of standard plastic biodegradative work by African scientists, and only a few works show detection of competent synthetic plastic degrading microbes globally. Asides from the ills of possible omission of core degraders, there is a need for researchers to follow standard degradation procedures to arrive at efficient, reproducible, and generally accepted outcomes utilizable on a larger scale. Thus, metagenomic search on the vast African urban and rural plastisphere is the best isolation option.
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Affiliation(s)
- Otobong Donald Akan
- College of Food Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 41004, China; Microbiology Department, Faculty of Biological Science, Akwa-Ibom State University, Ikot Akpaden, Mkpat Enin LGA, Uyo P.M.B., 1167, Akwa-Ibom State, Nigeria.
| | - Godwin Evans Udofia
- Department of Microbiology, Faculty of Science, University of Uyo, Uyo PMB, 1017, Nigeria
| | - Emmanuel Sunday Okeke
- Environmental Chemistry and Toxicology, School of Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China; Department of Biochemistry, Faculty of Biological Sciences & Natural Science Unit, School of General Studies University of Nigeria, Nsukka, 410001, Nigeria.
| | - Chiamaka Linda Mgbechidinma
- Ocean College, Zhejiang University, Zhoushan, 316021, Zhejiang, China; Department of Microbiology, University of Ibadan, Ibadan, Oyo State, 200243, Nigeria
| | - Charles Obinwanne Okoye
- Biofuels Institute, School of Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China; Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, 410001, Nigeria
| | - Yedomon Ange Bovys Zoclanclounon
- Department of Crop Science and Biotechnology, Jeonbuk National University, Jeonju, 54896, South Korea; Department of Management of Environment, Polytechnic School of Abomey-Calavi, University of Abomey-Calavi, 01 POB 2009, Cotonou, Benin
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12
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Mohanan N, Montazer Z, Sharma PK, Levin DB. Microbial and Enzymatic Degradation of Synthetic Plastics. Front Microbiol 2020; 11:580709. [PMID: 33324366 PMCID: PMC7726165 DOI: 10.3389/fmicb.2020.580709] [Citation(s) in RCA: 233] [Impact Index Per Article: 58.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022] Open
Abstract
Synthetic plastics are pivotal in our current lifestyle and therefore, its accumulation is a major concern for environment and human health. Petroleum-derived (petro-)polymers such as polyethylene (PE), polyethylene terephthalate (PET), polyurethane (PU), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) are extremely recalcitrant to natural biodegradation pathways. Some microorganisms with the ability to degrade petro-polymers under in vitro conditions have been isolated and characterized. In some cases, the enzymes expressed by these microbes have been cloned and sequenced. The rate of polymer biodegradation depends on several factors including chemical structures, molecular weights, and degrees of crystallinity. Polymers are large molecules having both regular crystals (crystalline region) and irregular groups (amorphous region), where the latter provides polymers with flexibility. Highly crystalline polymers like polyethylene (95%), are rigid with a low capacity to resist impacts. PET-based plastics possess a high degree of crystallinity (30-50%), which is one of the principal reasons for their low rate of microbial degradation, which is projected to take more than 50 years for complete degraded in the natural environment, and hundreds of years if discarded into the oceans, due to their lower temperature and oxygen availability. The enzymatic degradation occurs in two stages: adsorption of enzymes on the polymer surface, followed by hydro-peroxidation/hydrolysis of the bonds. The sources of plastic-degrading enzymes can be found in microorganisms from various environments as well as digestive intestine of some invertebrates. Microbial and enzymatic degradation of waste petro-plastics is a promising strategy for depolymerization of waste petro-plastics into polymer monomers for recycling, or to covert waste plastics into higher value bioproducts, such as biodegradable polymers via mineralization. The objective of this review is to outline the advances made in the microbial degradation of synthetic plastics and, overview the enzymes involved in biodegradation.
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Affiliation(s)
- Nisha Mohanan
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, Canada
| | - Zahra Montazer
- Faculty of Food Engineering, The Educational Complex of Agriculture and Animal Science, Torbat-e-jam, Iran
| | - Parveen K. Sharma
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, Canada
| | - David B. Levin
- Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, Canada
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