Next Article in Journal
Fabrication of Novel Agrowaste (Banana and Potato Peels)-Based Biochar/TiO2 Nanocomposite for Adsorption of Cr(VI), Statistical Optimization via RSM Approach
Next Article in Special Issue
Rutting Behaviour of Geopolymer and Styrene Butadiene Styrene-Modified Asphalt Binder
Previous Article in Journal
Natural Biopolymers as Additional Tools for Cell Microencapsulation Applied to Cellular Therapy
Previous Article in Special Issue
Partial Biodegradable Blend with High Stability against Biodegradation for Fused Deposition Modeling
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

A Bibliometric Analysis of Research Trends in Biodegradation of Plastics

by
Enoch Akinbiyi Akinpelu
* and
Felix Nchu
Department of Horticultural Sciences, Faculty of Applied Sciences, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535, South Africa
*
Author to whom correspondence should be addressed.
Polymers 2022, 14(13), 2642; https://doi.org/10.3390/polym14132642
Submission received: 23 May 2022 / Revised: 6 June 2022 / Accepted: 6 June 2022 / Published: 29 June 2022
(This article belongs to the Special Issue Durability and Degradation of Polymeric Materials)

Abstract

:
The rapid growth in the production and application of plastic globally has resulted in plastic pollution with a negative impact on the environment, especially the marine ecosystem. One main disadvantage in the majority of polymers is disposal after a useful life span. Non-degradable polymers create severe difficulty in plastic waste management that might end up in landfills or wash into the ocean. The biodegradation of plastic waste is one solution to this critical problem of pollution. Hence, there is a need to consider the advancement of research in this subject area, in pursuit of a way out of plastic pollution. Thus, this study was designed to map the biodegradation of plastic-related research from 2000 to 2021. Statistical information on the topic was recovered from the Web of Science Core Collection and analysed using the bibliometrix package in RStudio statistical software, while data visualisation was conducted via VOSviewer. Our evaluation indicated that the amount of research on the biodegradation of plastic increased over the last decade, and the annual growth rate of publication trends was 11.84%. The study revealed that 1131 authors wrote the 290 analysed documents, with a collaboration index of 4.04. Cooper DG (n = 11) was the most relevant author, McGill University (n = 21) was the most active university, and the Journal of Polymers and the Environment (n = 19) the leading journal. The outcome of this study can guide prospective research and offer vital information for improving the management of plastic waste.

1. Introduction

Plastics are synthetic or semi-synthetic materials made through the polymerisation of organic and/or inorganic compounds [1,2]. Because of their vast domestic and industrial applications, there is a continuous increase in the production and consumption of plastics. As of 2017, 8.3 billion metric tonnes of original plastics have been produced, of which 76% became waste. Only 9% of plastic waste is recycled, 12% incinerated, and 79% ends up in landfills [3,4]. The majority of bio-based and petroleum-based plastics, such as polyethylene, polypropylene, polyvinyl chloride, and polystyrene, are not biodegradable. Consequently, the build-up of non-biodegradable plastics in soil resulted in decreased soil fertility, among other ecological and health challenges [5,6]. Similarly, plastic materials are difficult to manage and often end up in marine environments, beaches and surfaces of the shallow seabed, as well as the abysses. The degradation of large polymers leads to the proliferation of micro-plastic particles, which are poisonous to marine species. The micro-plastic particles aid the accumulation of other contaminants capable of impairing the feeding and growth of aquatic organisms, thus, damaging the robustness of marine species [3,7]. Therefore, researchers and other stakeholders have shown huge interest to surmount the build-up of non-biodegradable plastics in the environment [1,8].
The biodegradation of plastics depends on some factors, such as the composition or molecular weight of the plastics, environmental conditions (e.g., temperature, soil reaction), and the presence of suitable microorganisms [5,9,10]. Because most polymers are too large to pass through the microbial cell membrane, the biodegradation of polymers often focuses on increasing surface hydrophobicity to enhance microbial attachment [5,7]. Several microorganisms (such as bacteria and fungi) have been identified with the capacity to biodegrade both bio-based and petroleum-based plastics through the activities of extracellular and intracellular depolymerase [9]. These microorganisms produce exoenzymes that break down complex polymers into monomers small enough to pass through the semi-permeable cell membrane and then be used as carbon and/or energy sources under stress conditions [1,5]. However, due to the complexity of structure and insufficient knowledge about optimised conditions for rapid degradation of plastic polymers, the share of biodegradable plastics for commercial applications is very low [11]. Therefore, it is essential to evaluate the scope of research activities capable of providing information on existing works, trends, scientific collaborations, and their impacts.
The bibliometric technique is a useful tool for evaluating the trends and evolution of research in a specific field of interest [12,13]. It utilises different techniques to quantify the scientific impact of published papers over the years to provide ideas/concepts and directions for future work [14,15]. Bibliometric analysis is popular in the scientific community because it can be used for mapping foci and trends linked to authors, institutions, and countries, including the identification of research gaps in a particular niche [16,17]. The Web of Science (WoS) and Scopus are typically used as a source for the mining of bibliometric data [18,19]. Thus far, there is no bibliometric report on the biodegradation of plastics; therefore, we assessed published articles on the biodegradation of plastics and scientific mapping was developed to identify top authors, journals, institutions, and countries, as well as collaborative networks from 2000 to 2021. This study provides an abridged database of knowledge where researchers can access important information on trends and existing gaps for future research that could increase the commercial application of the biodegradation of plastics.

2. Materials and Methods

2.1. Data Mining

Numerous scientific databases can be mined for information on bibliometric analysis of research production in a specific field [18,20]. WoS is one of the most dependable and all-inclusive databases for bibliometric studies with millions of varying quality and high-impact scientific articles [16]. Thus, WoS core collection was mined for data on bibliometric analysis of research trends on biodegradation of plastics from 2000 to 2021. The search strategy was: TITLE ((“Biodegradation” OR “biological degradation” OR “microbial degradation” OR “enzymatic degradation”) AND (*plastic* OR “polymer”)). A set of documents (n = 456) were retrieved but the search was refined to scientific research articles (n = 374). Afterwards, manual validation to remove those articles that are not within the time range and do not relate with our focus by going through all the abstracts was performed, of which 84 articles were excluded. As such, 290 articles were found suitable for bibliometric analysis in this study. These documents were retrieved from WoS and saved for further processing.

2.2. Data Analysis

Rstudio (v.4.1.1) was used for data analysis. The mined data were uploaded into biblioshiny in Rstudio and analysed accordingly [21]. Consequently, VOSviewer software version 1.6.17 [22] was used to determine the institutions’ and authors’ collaboration networks on the biodegradation of plastic within the stipulated period.

3. Results and Discussion

3.1. Key Information about Data (2000 to 2021)

Details of the main information on the biodegradation-of-plastics-related research are shown in Table 1. The 290 articles exported from WoS were published in 145 sources by 1131 authors. The average years from the publication were 8.46, the mean citations/documents were 23.74, and mean citations/year/document was 3.105, with a total reference of 8620 for the 290 articles. Authors of multi-authored documents totalled 1119 and authors of single-authored documents were 12. Meanwhile, the number of single-authored documents was 13. The documents/author and authors/document are 0.256 and 3.9, respectively. Co-authors/documents were 4.57 and the collaboration index was 4.04. The value of the collaboration index signifies high research collaboration, which might be seen as signified by the average citations per document [23].

3.2. Annual Production Trends

Variations in the number of published research documents in a specific field are an important pointer for the developmental trend [24]. A plot of publications over time with statistical assessment would play a part in comprehending the research condition as well as prospective trends. About 55% of the documents were published between 2015 and 2021—Figure 1a. The highest publication was observed in 2020 with 36 documents, accounting for 12.4% of the total documents. The observed annual growth rate was 11.84%, an indication of a positive research trend in the biodegradation of plastics over time. The growing public attention to the circular economy of plastic pollution and the efficient biodegradation approach may be responsible for the upsurge in publications. Microorganisms with the potential for efficient plastic degradation could result in new prospects for palliating plastic pollution. Globally, the top five productive countries in biodegradation-of-plastics-related research are China with the highest number of documents (n = 92), followed by the USA (n = 82), India (n = 47), Japan (n = 45), and Canada (n = 31). Though China accounts for the largest production of plastic materials globally [25,26], China still makes a significant effort to remove plastic pollution through the implementation of policies and numerous funded projects. Countries with the greatest contribution are shown in Figure 1b, where the darker the blue colour, the greater the number of documents published. Most of the countries with the greatest contribution are economically developed or developing nations that ascribe huge significance to scientific research and they publish in journals indexed in WoS. Though the statistic from WoS may not be a true representation of all published scientific articles in a specific field, because some researchers are indifferent about the journals’ quality or they are interested in journals with fast publications only without considering visibility. Similarly, mean total citations per year were analysed over the same period and there is variation in the citation pattern. The highest citation was observed in 2017, followed by 2020, whereas the least citations were observed in 2005. Numerous factors can affect the citation of a research document. These include year of publication and open or paid access journal. Older publications are expected to have more citations than new ones [27]. However, papers in open access journals are easily available to other scholars and, thus, more cited than those in paid access. Citations are presumed to indicate the quality of the research, though in some cases, this is not so. The relationship between research quality and citations is a continuous debate in scientometrics [28].

3.3. Relevant Institutions and Authors

The most relevant institution in biodegradation-of-plastics-related research in terms of publication between 2000 and 2021 was McGill University, Canada, with 21 publications, followed by Universiti Putra Malaysia (n = 10), N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences (n = 7), Agricultural University of Athens (n = 6), and China Pharmaceutical University (n = 6). Details of the top 20 relevant institutions are shown in Table 2. Several studies have used bibliometrics to assess relevant institutions and authors in a specific field of interest [29,30].
The data from WoS revealed that 1131 authors wrote the 290 documents used for the analysis, with 3.9 authors per document—Table 1. The productivity and citation impact of authors were analysed as a function of h_index in Rstudio. The top five authors are Cooper DG (n = 11, total citations = 315, h_index =8), Nicell JA (n = 9, total citations = 236, h_index = 7), Briassoulis D (n = 6, total citations = 510, h_index = 6), Degli-Innocenti, F (n = 5, total citations = 191, h_index = 5), and Tosin, M (n = 5, total citations = 189, h_index = 5)—Table 3. Most of the Cooper DG publications are focused on the application of microorganisms, such as Bacillus subtilis, Rhodococcus rhodochrous, Rhodotorula rubra, and aerobic mesophilic microorganisms, consisting of bacteria, fungi, and yeast, for the degradation of different plastic materials [31,32,33,34]. H_index is a true indicator of researchers’ contribution and attainment but it is not suitable for assessing multidisciplinary fields [35,36]. Likewise, citations are a deficient method of quantifying an author’s impact in a field, since many issues affect the citation of a research publication [37]. In our analysis, although Cooper DG has the highest number of publications (n = 11), he is not among the top five researchers with the highest total citations. They are Wu WM (752 total citations), Yang Y (689 total citations), Yang J (644 total citations), Jiang L (641 total citations), and Briassoilis D (510 total citations). Year of publication is one of those factors influencing paper citations, notwithstanding the publication year (2002) of Cooper DG, Wu WM, Yang Y, Yang J, and Jiang L, whose publication year was 2014, as well as Briassoulis D with a publication year of 2007, attained higher citation than Cooper DG.

3.4. Relevant Journals

The distributions of research scope in a specific topic are best explained in journals and subject categories in bibliometric analysis [38]. A total of 125 journals published the 290 documents analysed. The top 20 productive journals represent 44% of the total publications. The most relevant journals on the subject are Journal of Polymers and the Environment (n = 19, IF = 3.667), Polymer Degradation and Stability (n = 15, IF = 4.63), Environmental Science and Technology (n = 10, IF = 9.028), Science of the Total Environment (n = 10, IF = 7.963), and International Biodeterioration and Biodegradation (n = 9, IF = 4.074), among others—Table 4. Environmental Science and Technology has the highest total citations (995), followed by Journal of Polymers and the Environment (total citations = 885), Science of the Total Environment (total citation = 440), Waste Management (total citations = 401), and Polymer Degradation and Stability (total citations = 396), among others. Notwithstanding, both Journal of Polymers and the Environment and Polymer Degradation and Stability have the highest h_index of 12 and publication year commencing from 2000.
The analysis of relevant journals showed that the studies in this field are more interdisciplinary, with a focus on the environment. Plastics are not only an environmental concern but also a hazard to microorganisms, soil, plants, human health, and the food chain, among others [39,40]. The increasing impact of plastics on the environment calls for an inclusive assessment of the ecological risk and effect on human health. Studies on the interaction among plastics, microorganisms, and human health may be a likely development in the biodegradation of plastics.

3.5. Bibliographic Coupling Analysis

Bibliographic coupling analysis is a comparison measure that uses citation analysis to establish the relationship between documents based on the number of references shared [41]. This is to affirm the probability that the documents treat similar subjects and generate an information map of the research authors, institutions, and journals to show the collaborative network in biodegradation-of-plastics-related research. In this study, bibliographic coupling of authors, journals, and institutions was carried out using the full counting method in VOSviewer software. For bibliographic coupling analysis, we chose a minimum of three documents and 23 journals to meet the criteria. The bibliographic coupling link strength with other sources was calculated for each journal. The 23 journals were grouped into four clusters of 10, 6, 4, and 3 items in VOSviewer. Environmental Science and Technology has the highest total link strength of 574 with 11 documents and 995 citations, followed by the Science of Total Environment with 10 documents, 440 citations, and 564 total link strength—Figure 2a. Similarly, 22 authors meet the threshold. However, some of the 22 authors are not connected. The most connected authors consist of 17 authors. The 17 authors were classified into four clusters of 5, 5, 5, and 2 items. Cooper, D.G. has the highest total link strength of 1325 with nine documents and 211 citations, followed by Nicell, J.A. with 996 total link strength, seven documents and 132 citations—Figure 2b. For the bibliometric coupling analysis of institutions, the number of citations was five, and only 22 institutions meet the threshold. The 22 institutions were classified into five clusters of 11, 4, 3, 2, and 2 items. Stanford University has the highest total link strength of 385 with five documents and 767 citations, followed by Beihang University and Beijing Genomics Institute (BGI), Shenzhen with similar total link strength of 355 with three documents and 641 citations Figure 2c.

3.6. Collaboration Network Analysis

Collaboration network analysis can offer useful data for individual scholars, institutions, and countries seeking cooperation partners or groups to expand their field of research and realise the purpose of academic exchange [24]. This analysis reveals the reality of scientific research and academic communication among authors, institutions, and countries at various levels [42]. In this study, co-authorship of authors, institutions, and countries was analysed using the full counting method in VOSviewer. For the author’s analysis, the maximum number of authors per document was fixed as 25 and 1151 authors were observed. When the minimum number of documents per author was five and the minimum number of citations of an author was zero, only five authors met the threshold. The minimum number of documents per author was further reduced to three and the number of authors that meet this requirement increased to 22. For the 22 authors, the total strength of co-authorship links with other authors was calculated. Only 5 of the 22 authors in the network are well connected. They are Wu WM, Jiang L, Yang Y, Zhao J, and Yang J. Subsequently, the connection among the five authors was visualised—Figure 3a.
For the institution’s collaboration analysis, with a maximum of 25 institutions per document, 404 institutions were observed. Only five institutions met the threshold when the minimum number of documents per institute was five and the minimum number of citations was zero. Reducing the minimum number of documents per institute to three increased the number of institutions to 22. Most of the 22 institutions are not linked. The biggest group of connected institutions is three; they are Stanford University, Beihang University, and BGI Shenzhen and the connection is shown in Figure 3b. These analyses show that there is no strong collaboration among authors and institutions in the biodegradation-of-plastics-related research. More effort is needed to promote academic exchange in the biological degradation of plastic.
For the country’s co-authorship analysis, 52 countries were observed with the maximum number of countries per document being 25. With a minimum of five documents in a country and the minimum number of citations as zero, 18 countries met the selected criteria. A further reduction in the minimum number of documents of a country to three increased the number of countries that satisfy the requirement to 32. Some of the 32 countries are not connected. The biggest group of connected countries consists of 21 countries. The 21 countries were grouped into five clusters of six, four, four, four, and three items in VOSviewers. Clusters are grouped by the rate of shared co-occurrence terms representing each country. Terms with the same colour indicate they are strongly connected, thereby classified into the same cluster—Figure 3c. The more research publications a country has, the bigger the size of its circle; the larger the scale of the cooperation is, the thicker the connecting line [43]. The line connecting two items is the measurement of the level of cooperation between the two terms and is called link strength. The highest link strength between countries is 9 and found between China and the USA. The top three counties with the highest link strength are the USA (1906 citations, 24 link strength), China (1428 citations, 16 link strength), and Switzerland (202 citations, 7 link strength). This analysis shows there is no country from Africa among the collaborating countries; hence, much work is needed in this research area in Africa.

3.7. Co-Occurrence of Author Keywords

Co-occurrence analysis can be used to identify current topics and directions to observe and follow up the advances in scientific research and programs [44,45]. We analysed the co-occurrence of the author’s keywords via VOSviewer, shown in Figure 4. The size of a keyword indicates the number of publications in which it occurs, and the distance between two keywords gives a rough estimate of the relationship of the keywords. Using the full counting method, 779 keywords were observed. With the minimum number of occurrences of a keyword fixed at five, only 28 keywords meet the threshold. When we reduced the minimum number of occurrences of a keyword to three, 65 keywords met the requirement. The topmost keywords are: Biodegradation (125 occurrences, 106 link strength), Enzymatic degradation (12 occurrences, 6 link strength), Plastics (11 occurrences, 18 link strength), Polyethylene (11 occurrences, 17 link strength), Biodegradable (11 occurrences, 15 link strength), Composting (10 occurrences, 18 link strength), Degradation (10 occurrences, 6 link strength), Biodegradability (9 occurrences, 9 link strength), Enzymes (8 occurrences, 10 link strength), and Microorganisms (7 occurrences, 10 link strength). These keywords are a reflection of the research focus on the subject over two decades among scholars, and various researchers have utilised keywords to ascertain research directions in a specific field [17,18,20].
The 65 keywords were divided into eleven clusters of 11, 8, 8, 8, 7, 6, 5, 5, 3, 3, and 1 item in VOSviewer. Each cluster is represented with a unique colour to show the relatedness of the items in the cluster [46]. The keywords in identical clusters normally exhibit stronger links. The node size indicates the number of occurrences of a keyword and the attached lines show the existing connection. Cluster 1 centres on different plastic additives as well as their degradation and is identified by keywords, such as “2-ethylhexanol”, “phthalate”, “dehp”, “plasticizer”, “polyesters”, and “plastic biodegradation”, among others. Different methods of degradation of plastic materials are categorised in Cluster 2, which were identified by keywords, such as “enzymatic degradation”, “hydrolytic degradation”, and “biocomposite”, among others. Cluster 3 identifies plastic biodegradation material keywords, namely “biodegradable materials”, “biodegradation in soil”, “biofilm”, “composting”, and “chitosan”, among others. Microbial degradation of plastic is an environmentally benign method of managing plastic pollution [47]. Most research on the biodegradation of plastic is focused on the terrestrial environment, with several microorganisms, such as “bacteria”, “fungi”, and “microbes”, keywords identified in Cluster 6 [48,49,50]. There are limited reports of research on marine plastic sources degrading microorganisms [7,51]. Cluster 7 focused on various forms of plastic accumulation in the environment and their biodegradation. The keywords in this cluster include “microplastics”, “plastic waste”, “polystyrene”, “polycaprolactone”, and “biodegradation”. Previous studies have shown that microplastics are a carrier of toxic substances and other contaminants, which when consumed by organisms, such as fishes and seabirds, could affect their agility, feeding pattern, and reproductive system [52,53,54]. In addition, microplastics have been detected in foods, sea salts, and bottled water, including human stool samples and human placenta [55,56,57,58]. This suggests that microplastics can cause an imbalance in the intestinal microbiota, such as intestinal dysfunction and metabolic disorder [59,60]. Hence, studies on microbial activities on microplastics and their associated impact on human health are among the vital research topics needed.

3.8. Co-Citation Analyses

This is meant to determine the relationship of items based on how often they are cited together. Co-citation analysis provides important information on a topic in a specific field of research from the bulk of cited sources, authors, and references, that can assist in the evaluation of the most significant publications on a specific subject [24]. In this study, co-citations of cited references, cited sources, and cited authors were analysed—Figure 5. For cited references, the minimum number of citations of a cited reference was set as 10 and 23 cited references were found to meet the threshold out of 8659 cited references in the 290 publications analysed. Some of the 23 items are not linked. The biggest group of connected items consists of 21 cited references. The 21 items were grouped into four clusters of eight, seven, five, and one item in VOSviewer. The top five cited items are Shah, AA 2008 (40 citations, 109 total link strength), Tokiwa, Y 2009 (20 citations, 57 total link strength), Yang, J 2014 (19 citations, 85 total link strength), Yoshida, S 2016 (19 citations, 55 total link strength), and Jambeck, Jr 2015 (18 citations, 54 total link strength)—Figure 5a.
Similarly, for the co-citation of authors, 6716 authors were identified. With the minimum number of citations of an author as 10, 72 authors meet the criteria. Some of the 72 items are not connected. The biggest group of connected items consists of 66 authors, and they are classified into four clusters of 26, 16, 15, and 9 items. The top five are Shah, AA (52 citations, 437 total link strength), Albertsson, AC (58 citations, 365 total link strength), Tokiwa, Y (47 citations, 321 total link strength), Yang, Y (35 citations, 222 total link strength), and Wei, R (33 citations, 205 total strength)—Figure 5b.
In addition, cited sources returned 2923 sources. When the minimum number of citations of a source was 10, 165 sources met the requirement. The 165 items were classified into five clusters of 54, 43, 36, 31, and 1 item. The top five cited sources are Polymer Degradation and Stability (511 citations, 12064 total link strength), Applied Environmental Microbiology (287 citations, 8832 total link strength), Environmental Science and Technology (245 citations, 6361 total link strength), Journal of Applied Polymer Science (212 citations, 4120 total link strength), and Chemosphere (201 citations, and 5299 total link strength)—Figure 5c.

4. Limitations

This study presents the mapping of biodegradation-of-plastic-related research between 2000 and 2021. Nevertheless, the analysis might not be all inclusive of research publications on the topic, seeing as we centred on publications indexed in the Web of Science, excluding publications indexed in PubMed and Scopus, among other scientific databases. Similarly, it is likely that we did not use up all the possible keywords connected to the biodegradation of plastics within the specified time, and that might have created a bias in our analysis. Lastly, this study solely visualised the research trends on the topic but did not analyse the substance of every publication to determine the scientific quality or otherwise of the paper.

5. Conclusions

This study presented a comprehensive scientific mapping of global research on the biodegradation of plastic-related research from 2000 to 2021. About 290 publications were recovered from the Web of Science, written by 1131 authors. The Peoples’ Republic of China and the USA were the most prominent countries, with the highest publications and citations. In addition, the most relevant journals are the Journal of Polymers and the Environment and Polymer Degradation and Stability on the subject. We observed a low collaboration network among authors, with the strongest collaboration network between China and the USA, and no African country on the collaboration network analysis. This study suggests that more studies should be focused on the biodegradation-of-plastic-related research that elucidates the concurrent impact of microbial communities and microplastics on both the environment and human health. We believe this study would assist scholars interested in this field to identify potential collaborators, as well as provide valuable information for the effective planning and management of plastic contaminants, especially in the coastal and marine environment.

Author Contributions

E.A.A. and F.N. conceptualised and designed the study. Material preparation, data collection, and analysis were performed by E.A.A. The first draft of the manuscript was written by E.A.A., and all authors reviewed the original draft of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

The research was funded by the Cape Peninsula University of Technology, University Research Fund (URF R166).

Institutional Review Board Statement

Not Applicable.

Informed Consent Statement

Not Applicable.

Data Availability Statement

Not Applicable.

Conflicts of Interest

The authors have no relevant financial or non-financial interest to disclose. Furthermore, the funders had no role in the design of the study; in the collection, analysis, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Ahmed, T.; Shahid, M.; Azeem, F.; Rasul, I.; Shah, A.A.; Noman, M.; Hameed, A.; Manzoor, N.; Manzoor, I.; Muhammad, S. Biodegradation of plastics: Current scenario and future prospects for environmental safety. Environ. Sci. Pollut. Res. 2018, 25, 7287–7298. [Google Scholar] [CrossRef] [PubMed]
  2. Saminathan, P.; Sripriya, A.; Nalini, K.; Sivakumar, T.; Thangapandian, V. Biodegradation of plastics by Pseudomonas putida isolated from garden soil samples. J. Adv. Bot. Zool. 2014, 1, 34–38. [Google Scholar]
  3. Wierckx, N.; Narancic, T.; Eberlein, C.; Wei, R.; Drzyzga, O.; Magnin, A.; Ballerstedt, H.; Kenny, S.T.; Pollet, E.; Avérous, L.; et al. Plastic Biodegradation: Challenges and Opportunities. In Consequences of Microbial Interactions with Hydrocarbons, Oils, and Lipids: Biodegradation and Bioremediation; Steffan, R.J., Ed.; Springer International Publishing: Cham, Switzerland, 2019; pp. 333–361. [Google Scholar]
  4. Geyer, R.; Jambeck, J.R.; Law, K.L. Production, use, and fate of all plastics ever made. Sci. Adv. 2017, 3, e1700782. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  5. Janczak, K.; Dąbrowska, G.B.; Raszkowska-Kaczor, A.; Kaczor, D.; Hrynkiewicz, K.; Richert, A. Biodegradation of the plastics PLA and PET in cultivated soil with the participation of microorganisms and plants. Int. Biodeterior. Biodegrad. 2020, 155, 105087. [Google Scholar] [CrossRef]
  6. Bettas Ardisson, G.; Tosin, M.; Barbale, M.; Degli-Innocenti, F. Biodegradation of plastics in soil and effects on nitrification activity. A laboratory approach. Front. Microbiol. 2014, 5, 710. [Google Scholar] [CrossRef] [Green Version]
  7. Sangeetha Devi, R.; Rajesh Kannan, V.; Nivas, D.; Kannan, K.; Chandru, S.; Robert Antony, A. Biodegradation of HDPE by Aspergillus spp. from marine ecosystem of Gulf of Mannar, India. Mar. Pollut. Bull. 2015, 96, 32–40. [Google Scholar] [CrossRef]
  8. Tokiwa, Y.; Calabia, B.; Ugwu, C.; Aiba, S. Biodegradability of Plastics. Int. J. Mol. Sci. 2009, 10, 3722. [Google Scholar] [CrossRef]
  9. Bano, K.; Kuddus, M.; Zaheer, M.R.; Zia, Q.; Khan, M.F.; Gupta, A.; Aliev, G. Microbial enzymatic degradation of biodegradable plastics. Curr. Pharm. Biotechnol. 2017, 18, 429–440. [Google Scholar]
  10. Gu, J.-G.; Gu, J.-D. Methods Currently Used in Testing Microbiological Degradation and Deterioration of a Wide Range of Polymeric Materials with Various Degree of Degradability: A Review. J. Polym. Environ. 2005, 13, 65–74. [Google Scholar] [CrossRef]
  11. Rujnić-Sokele, M.; Pilipović, A. Challenges and opportunities of biodegradable plastics: A mini review. Waste Manag. Res. 2017, 35, 132–140. [Google Scholar] [CrossRef]
  12. Ma, X.; Gao, M.; Gao, Z.; Wang, J.; Zhang, M.; Ma, Y.; Wang, Q. Past, current, and future research on microalga-derived biodiesel: A critical review and bibliometric analysis. Environ. Sci. Pollut. Res. 2018, 25, 10596–10610. [Google Scholar] [CrossRef] [PubMed]
  13. Lu, K.; Yu, S.; Sun, D.; Xing, H.; An, J.; Kong, C.; Yu, M.; Zhu, Y. Scientometric Analysis of SIRT6 Studies. Med. Sci. Monit. Int. Med. J. Exp. Clin. Res. 2018, 24, 8357–8371. [Google Scholar] [CrossRef] [PubMed]
  14. Roldan-Valadez, E.; Salazar-Ruiz, S.Y.; Ibarra-Contreras, R.; Rios, C. Current concepts on bibliometrics: A brief review about impact factor, Eigenfactor score, CiteScore, SCImago Journal Rank, Source-Normalised Impact per Paper, H-index, and alternative metrics. Ir. J. Med. Sci. 2019, 188, 939–951. [Google Scholar] [CrossRef] [PubMed]
  15. Wang, C.-Y.; Li, B.-H.; Ma, L.-L.; Zhao, M.-J.; Deng, T.; Jin, Y.-H.; Ren, X.-Q. The Top-100 Highly Cited Original Articles on Drug Therapy for Ventilator-Associated Pneumonia. Front. Pharmacol. 2019, 10, 108. [Google Scholar] [CrossRef] [Green Version]
  16. Can-Güven, E. Microplastics as emerging atmospheric pollutants: A review and bibliometric analysis. Air Qual. Atmos. Health 2021, 14, 203–215. [Google Scholar] [CrossRef]
  17. Wong, S.L.; Nyakuma, B.B.; Wong, K.Y.; Lee, C.T.; Lee, T.H.; Lee, C.H. Microplastics and nanoplastics in global food webs: A bibliometric analysis (2009–2019). Mar. Pollut. Bull. 2020, 158, 111432. [Google Scholar] [CrossRef]
  18. Simões, A.J.A.; Macêdo-Júnior, R.O.; Santos, B.L.P.; Silva, D.P.; Ruzene, D.S. A Bibliometric Study on the Application of Advanced Oxidation Processes for Produced Water Treatment. Water Air Soil Pollut. 2021, 232, 297. [Google Scholar] [CrossRef]
  19. Okaiyeto, K.; Oguntibeju, O.O. Trends in diabetes research outputs in South Africa over 30 years from 2010 to 2019: A bibliometric analysis. Saudi J. Biol. Sci. 2021, 28, 2914–2924. [Google Scholar] [CrossRef]
  20. Gan, Z.; Zhang, H. PMBD: A comprehensive plastics microbial biodegradation database. Database 2019, 2019, baz119. [Google Scholar] [CrossRef]
  21. Aria, M.; Cuccurullo, C. Bibliometrix: An R-tool for comprehensive science mapping analysis. J. Informetr. 2017, 11, 959–975. [Google Scholar] [CrossRef]
  22. Van Eck, N.; Waltman, L. Software survey: VOSviewer, a computer program for bibliometric mapping. Scientometrics 2010, 84, 523–538. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  23. Siamaki, S.; Geraei, E.; Zare-Farashbandi, F. A study on scientific collaboration and co-authorship patterns in library and information science studies in Iran between 2005 and 2009. J. Educ. Health Promot. 2014, 3, 99. [Google Scholar] [PubMed]
  24. Mao, X.; Chen, C.; Wang, B.; Hou, J.; Xiang, C. A global bibliometric and visualized analysis in the status and trends of subchondral bone research. Medicine 2020, 99, e20406. [Google Scholar] [CrossRef] [PubMed]
  25. Wang, W.; Yuan, W.; Chen, Y.; Wang, J. Microplastics in surface waters of Dongting Lake and Hong Lake, China. Sci. Total Environ. 2018, 633, 539–545. [Google Scholar] [CrossRef]
  26. Jiang, Y.; Xia, W.; Zhao, R.; Wang, M.; Tang, J.; Wei, Y. Insight into the Interaction between Microplastics and Microorganisms Based on a Bibliometric and Visualized Analysis. Bull. Environ. Contam. Toxicol. 2021, 107, 585–596. [Google Scholar] [CrossRef]
  27. Aksnes, D.W.; Langfeldt, L.; Wouters, P. Citations, citation indicators, and research quality: An overview of basic concepts and theories. Sage Open 2019, 9, 1–17. [Google Scholar] [CrossRef] [Green Version]
  28. Leydesdorff, L.; Bornmann, L.; Comins, J.A.; Milojević, S. Citations: Indicators of Quality? The Impact Fallacy. Front. Res. Metr. Anal. 2016, 1, 1. [Google Scholar] [CrossRef] [Green Version]
  29. Ekundayo, T.C.; Olasehinde, T.A.; Okaiyeto, K.; Okoh, A.I. Microbial Pathogenesis and Pathophysiology of Alzheimer’s Disease: A Systematic Assessment of Microorganisms’ Implications in the Neurodegenerative Disease. Front. Neurosci. 2021, 15, 648484. [Google Scholar] [CrossRef]
  30. Arshad, A.I.; Ahmad, P.; Karobari, M.I.; Asif, J.A.; Alam, M.K.; Mahmood, Z.; Abd Rahman, N.; Mamat, N.; Kamal, M.A. Antibiotics: A Bibliometric Analysis of Top 100 Classics. Antibiotics 2020, 9, 219. [Google Scholar] [CrossRef]
  31. Trinh Tan, F.; Cooper, D.G.; Marić, M.; Nicell, J.A. Biodegradation of a synthetic co-polyester by aerobic mesophilic microorganisms. Polym. Degrad. Stab. 2008, 93, 1479–1485. [Google Scholar] [CrossRef]
  32. Sauvageau, D.; Cooper, D.G.; Nicell, J.A. Relative rates and mechanisms of biodegradation of diester plasticizers mediated by Rhodococcus rhodochrous. Can. J. Chem. Eng. 2009, 87, 499–506. [Google Scholar] [CrossRef]
  33. Grochowalski, A.R.; Cooper, D.G.; Nicell, J.A. Effect of surfactants on plasticizer biodegradation by Bacillus subtilis ATCC 6633. Biodegradation 2007, 18, 283–293. [Google Scholar] [CrossRef] [PubMed]
  34. Gartshore, J.; Cooper, D.G.; Nicell, J.A. Biodegradation of plasticizers by Rhodotorula rubra. Environ. Toxicol. Chem. 2003, 22, 1244–1251. [Google Scholar] [CrossRef] [PubMed]
  35. Miao, Y.; Zhang, Y.; Yin, L. Trends in hepatocellular carcinoma research from 2008 to 2017: A bibliometric analysis. PeerJ 2018, 6, e5477. [Google Scholar] [CrossRef]
  36. Guilak, F.; Jacobs, C.R. The H-index: Use and overuse. J. Biomech. 2011, 44, 208–209. [Google Scholar] [CrossRef]
  37. Stern, R.S.; Arndt, K.A. Top cited authors in dermatology: A citation study from 24 journals: 1982–1996. Arch. Dermatol. 1999, 135, 299–302. [Google Scholar] [CrossRef] [Green Version]
  38. Leydesdorff, L.; Rafols, I. A global map of science based on the ISI subject categories. J. Am. Soc. Inf. Sci. Technol. 2009, 60, 348–362. [Google Scholar] [CrossRef] [Green Version]
  39. Barboza, L.G.A.; Dick Vethaak, A.; Lavorante, B.R.B.O.; Lundebye, A.-K.; Guilhermino, L. Marine microplastic debris: An emerging issue for food security, food safety and human health. Mar. Pollut. Bull. 2018, 133, 336–348. [Google Scholar] [CrossRef]
  40. Yang, Y.; Liu, W.; Zhang, Z.; Grossart, H.-P.; Gadd, G.M. Microplastics provide new microbial niches in aquatic environments. Appl. Microbiol. Biotechnol. 2020, 104, 6501–6511. [Google Scholar] [CrossRef]
  41. Kessler, M.M. Bibliographic coupling between scientific papers. Am. Doc. 1963, 14, 10–25. [Google Scholar] [CrossRef]
  42. Han, P.; Shi, J.; Li, X.; Wang, D.; Shen, S.; Su, X. International collaboration in LIS: Global trends and networks at the country and institution level. Scientometrics 2014, 98, 53–72. [Google Scholar] [CrossRef]
  43. Deng, Z.; Wang, H.; Chen, Z.; Wang, T. Bibliometric Analysis of Dendritic Epidermal T Cell (DETC) Research From 1983 to 2019. Front. Immunol. 2020, 11, 259. [Google Scholar] [CrossRef] [PubMed]
  44. Gao, Y.; Wang, Y.; Zhai, X.; He, Y.; Chen, R.; Zhou, J.; Li, M.; Wang, Q. Publication trends of research on diabetes mellitus and T cells (1997–2016): A 20-year bibliometric study. PLoS ONE 2017, 12, e0184869. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  45. Li, T.; Ho, Y.-S.; Li, C.-Y. Bibliometric analysis on global Parkinson’s disease research trends during 1991–2006. Neurosci. Lett. 2008, 441, 248–252. [Google Scholar] [CrossRef]
  46. Palmblad, M.; van Eck, N.J. Bibliometric Analyses Reveal Patterns of Collaboration between ASMS Members. J. Am. Soc. Mass Spectrom. 2018, 29, 447–454. [Google Scholar] [CrossRef] [Green Version]
  47. Ji, J.; Zhang, Y.; Liu, Y.; Zhu, P.; Yan, X. Biodegradation of plastic monomer 2,6-dimethylphenol by Mycobacterium neoaurum B5-4. Environ. Pollut. 2020, 258, 113793. [Google Scholar] [CrossRef]
  48. Sheik, S.; Chandrashekar, K.R.; Swaroop, K.; Somashekarappa, H.M. Biodegradation of gamma irradiated low density polyethylene and polypropylene by endophytic fungi. Int. Biodeterior. Biodegrad. 2015, 105, 21–29. [Google Scholar] [CrossRef]
  49. Mehmood, C.T.; Qazi, I.A.; Hashmi, I.; Bhargava, S.; Deepa, S. Biodegradation of low density polyethylene (LDPE) modified with dye sensitized titania and starch blend using Stenotrophomonas pavanii. Int. Biodeterior. Biodegrad. 2016, 113, 276–286. [Google Scholar] [CrossRef]
  50. Li, Z.; Wei, R.; Gao, M.; Ren, Y.; Yu, B.; Nie, K.; Xu, H.; Liu, L. Biodegradation of low-density polyethylene by Microbulbifer hydrolyticus IRE-31. J. Environ. Manag. 2020, 263, 110402. [Google Scholar] [CrossRef]
  51. Harshvardhan, K.; Jha, B. Biodegradation of low-density polyethylene by marine bacteria from pelagic waters, Arabian Sea, India. Mar. Pollut. Bull. 2013, 77, 100–106. [Google Scholar] [CrossRef]
  52. Jabeen, K.; Su, L.; Li, J.; Yang, D.; Tong, C.; Mu, J.; Shi, H. Microplastics and mesoplastics in fish from coastal and fresh waters of China. Environ. Pollut. 2017, 221, 141–149. [Google Scholar] [CrossRef] [PubMed]
  53. Carbery, M.; O’Connor, W.; Palanisami, T. Trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health. Environ. Int. 2018, 115, 400–409. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  54. Provencher, J.F.; Vermaire, J.C.; Avery-Gomm, S.; Braune, B.M.; Mallory, M.L. Garbage in guano? Microplastic debris found in faecal precursors of seabirds known to ingest plastics. Sci. Total Environ. 2018, 644, 1477–1484. [Google Scholar] [CrossRef] [PubMed]
  55. Ragusa, A.; Svelato, A.; Santacroce, C.; Catalano, P.; Notarstefano, V.; Carnevali, O.; Papa, F.; Rongioletti, M.C.A.; Baiocco, F.; Draghi, S.; et al. Plasticenta: First evidence of microplastics in human placenta. Environ. Int. 2021, 146, 106274. [Google Scholar] [CrossRef] [PubMed]
  56. Schwabl, P.; Köppel, S.; Königshofer, P.; Bucsics, T.; Trauner, M.; Reiberger, T.; Liebmann, B. Detection of various microplastics in human stool: A prospective case series. Ann. Intern. Med. 2019, 171, 453–457. [Google Scholar] [CrossRef] [PubMed]
  57. Yang, D.; Shi, H.; Li, L.; Li, J.; Jabeen, K.; Kolandhasamy, P. Microplastic Pollution in Table Salts from China. Environ. Sci. Technol. 2015, 49, 13622–13627. [Google Scholar] [CrossRef]
  58. Mason, S.A.; Welch, V.G.; Neratko, J. Synthetic Polymer Contamination in Bottled Water. Front. Chem. 2018, 6, 407. [Google Scholar] [CrossRef] [Green Version]
  59. Chi, Y.; Lin, Y.; Lu, Y.; Huang, Q.; Ye, G.; Dong, S. Gut microbiota dysbiosis correlates with a low-dose PCB126-induced dyslipidemia and non-alcoholic fatty liver disease. Sci. Total Environ. 2019, 653, 274–282. [Google Scholar] [CrossRef]
  60. Zhang, L.; Nichols, R.G.; Correll, J.; Murray, I.A.; Tanaka, N.; Smith, P.B.; Hubbard, T.D.; Sebastian, A.; Albert, I.; Hatzakis, E.; et al. Persistent Organic Pollutants Modify Gut Microbiota–Host Metabolic Homeostasis in Mice through Aryl Hydrocarbon Receptor Activation. Environ. Health Perspect. 2015, 123, 679–688. [Google Scholar] [CrossRef] [Green Version]
Figure 1. (a) Annual production and average citation per annum on biodegradation-of-plastics-related research from 2000 to 2021. (b) Country scientific production on biodegradation-of-plastics-related research.
Figure 1. (a) Annual production and average citation per annum on biodegradation-of-plastics-related research from 2000 to 2021. (b) Country scientific production on biodegradation-of-plastics-related research.
Polymers 14 02642 g001
Figure 2. Bibliographic coupling analysis of (a) journals, (b) authors, and (c) institutions.
Figure 2. Bibliographic coupling analysis of (a) journals, (b) authors, and (c) institutions.
Polymers 14 02642 g002aPolymers 14 02642 g002b
Figure 3. (a). Collaborative network analysis of authors in biodegradation-of-plastics-related research between 2000 and 2021. (b). Collaborative network analysis of institutions in biodegradation-of-plastics-related research between 2000 and 2021. (c). Collaborative network analysis of countries in biodegradation-of-plastics-related research between 2000 and 2021.
Figure 3. (a). Collaborative network analysis of authors in biodegradation-of-plastics-related research between 2000 and 2021. (b). Collaborative network analysis of institutions in biodegradation-of-plastics-related research between 2000 and 2021. (c). Collaborative network analysis of countries in biodegradation-of-plastics-related research between 2000 and 2021.
Polymers 14 02642 g003aPolymers 14 02642 g003b
Figure 4. Co-occurrence of author keywords in biodegradation-of-plastics-related research between 2000 and 2021.
Figure 4. Co-occurrence of author keywords in biodegradation-of-plastics-related research between 2000 and 2021.
Polymers 14 02642 g004
Figure 5. (a) Co-citation of cited references in biodegradation-of-plastics-related research between 2000 and 2021. (b) Co-citation of cited authors in biodegradation-of-plastics-related research between 2000 and 2021. (c) Co-citation of cited sources in biodegradation-of-plastics-related research between 2000 and 2021.
Figure 5. (a) Co-citation of cited references in biodegradation-of-plastics-related research between 2000 and 2021. (b) Co-citation of cited authors in biodegradation-of-plastics-related research between 2000 and 2021. (c) Co-citation of cited sources in biodegradation-of-plastics-related research between 2000 and 2021.
Polymers 14 02642 g005aPolymers 14 02642 g005b
Table 1. Major information on biodegradation of plastics-related research from 2000 to 2021.
Table 1. Major information on biodegradation of plastics-related research from 2000 to 2021.
DescriptionResults
Timespan2000:2021
Sources (Journals, Books, etc.)145
Documents290
Average years from publication8.46
Average citations per document23.74
Average citations per year per doc3.105
References8620
DOCUMENT TYPES
article261
article; early access5
article; proceedings paper12
correction4
editorial material8
DOCUMENT CONTENTS
Keywords Plus (ID)811
Author’s Keywords (DE)778
AUTHORS
Authors1131
Author Appearances1325
Authors of single-authored documents12
Authors of multi-authored documents1119
AUTHORS COLLABORATION
Single-authored documents13
Documents per Author0.256
Authors per Document3.9
Co-Authors per Documents4.57
Collaboration Index4.04
Table 2. Top relevant institutions in biodegradation-of-plastics-related research between 2000 and 2021.
Table 2. Top relevant institutions in biodegradation-of-plastics-related research between 2000 and 2021.
InstitutionsNumber of Articles
MCGILL UNIV21
UNIV PUTRA MALAYSIA10
NM EMANUEL INST BIOCHEM PHYS7
AGR UNIV ATHENS6
CHINA PHARMACEUT UNIV6
UNIV MINHO6
BEIHANG UNIV5
KASETSART UNIV5
MICHIGAN STATE UNIV5
SHAANXI UNIV SCI AND TECHNOL5
SHANGHAI JIAO TONG UNIV5
STANFORD UNIV5
UNIV FED SAO JOAO DEL REI5
EINDHOVEN UNIV TECHNOL4
INHA UNIV4
JOHNS HOPKINS UNIV4
LEHIGH UNIV4
MENDEL UNIV BRNO4
NATL CTR AGR UTILIZAT RES4
NN SEMENOV CHEM PHYS INST4
Table 3. Top relevant authors in biodegradation-of-plastics-related research between 2000 and 2021.
Table 3. Top relevant authors in biodegradation-of-plastics-related research between 2000 and 2021.
Authorsh_Indexg_Indexm_IndexTCNPPY_StartAF
Cooper DG8110.3813151120023.10
Nicell JA790.333236920022.57
Briassoulis D660.375510620072.50
Degli-innocenti F550.556191520142.25
Tosin M550.556189520141.50
Maric M440.364108420120.90
Wu WM440.444752420140.57
Yang Y440.444689420140.78
Bellon-maurel V330.13118320000.70
Erythropel HC330.273101320120.70
Feuilloley P330.13118320000.70
Gori R330.37569320150.67
Jiang L330.333641320140.45
Kasuya K330.1341320000.67
Kim MN330.14362320020.75
Kohler HPE330.143148320020.56
Nalli S330.143146320021.00
Silvestre F330.13118320000.70
Watanabe T330.21425320090.54
Yang J340.333644420140.78
TC: total citation, NP: Number of publications, PY: Publication Year, AF: Article Fractionalised.
Table 4. Relevant journals in biodegradation-of-plastics-related research between 2000 and 2021.
Table 4. Relevant journals in biodegradation-of-plastics-related research between 2000 and 2021.
Journalsh_Indexg_Indexm_IndexTCNPPY_Start
Journal of Polymers and the Environment12190.522885192000
Polymer Degradation and Stability12150.5217396152000
Environmental Science & Technology10100.4762995102002
Science of the Total Environment8100.4706440102006
International Biodeterioration & Biodegradation990.473721392004
Journal of Applied Polymer Science790.304326492000
Chemosphere780.304320982000
Environmental Science and Pollution Research660.260918562000
Journal of Hazardous Materials550.384624552010
Biodegradation440.190510842002
Biomacromolecules440.173922542000
International Journal of Biological Macromolecules340.30008942013
Polimery340.14294942002
Polymer Testing440.181814842001
Canadian Journal of Chemical Engineering330.13042332000
Environmental Technology230.25001632015
Journal of Bioscience and Bioengineering330.13043732000
Polymers230.40003332018
Waste Management330.250040132011
3 Biotech220.22222122014
TC: total citation, NP: Number of publications, PY: Publication Year.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Akinpelu, E.A.; Nchu, F. A Bibliometric Analysis of Research Trends in Biodegradation of Plastics. Polymers 2022, 14, 2642. https://doi.org/10.3390/polym14132642

AMA Style

Akinpelu EA, Nchu F. A Bibliometric Analysis of Research Trends in Biodegradation of Plastics. Polymers. 2022; 14(13):2642. https://doi.org/10.3390/polym14132642

Chicago/Turabian Style

Akinpelu, Enoch Akinbiyi, and Felix Nchu. 2022. "A Bibliometric Analysis of Research Trends in Biodegradation of Plastics" Polymers 14, no. 13: 2642. https://doi.org/10.3390/polym14132642

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop