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Life
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Microbial Biopolymers: From Synthesis to Properties and Applications
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Microbial Biopolymers: From Synthesis to Properties and Applications

A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Microbiology".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 18623

Special Issue Editor

Dr. Filomena Freitas

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Guest Editor
Associate Laboratory i4HB – Institute for Health and Bioeconomy, and UCIBIO – Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
Interests: biological valorization of agro-industrial byproducts; microbial bioprocesses; biopolymers: production and applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Biopolymers of microbial origin, such as polysaccharides, polyamides, and polyhydroxyalkanoates, have been extensively studied, and many of them are already being exploited in many areas, from commodity products to high-value medical and pharmaceutical applications. They are represented by a large variety of materials characterized by valuable properties, ranging from hydrocolloids to thermoplastics and including bioactive macromolecules. Microbial biopolymers present many advantages over their synthetic counterparts which is mainly related to the biodegradability and biocompatibility already demonstrated for many of them, and their more sustainable production processes. The use of microorganisms for biopolymer production also presents advantages over the use of other natural sources, plants, macroalgae, or animals as they are more amenable to control through cultivation conditions, by passing complications due to climate, pollution, and seasonality, thus assuring the quality and quantity of the final products. More importantly, microbial biopolymers frequently display properties not found in other natural or synthetic polymers, which opens the opportunity for novel applications in such high-value areas as biomedicine, cosmetics, and nutrition.

This Special Issue on “Microbial Biopolymers: From Synthesis to Properties and Applications” will therefore present original research papers and comprehensive reviews that integrate the expertise from different areas related to microbial biopolymers, from production processes, biosynthetic pathways, and metabolic engineering to biopolymer recovery, characterization, and applications.

You may choose our Joint Special Issue in Bioengineering.

Dr. Filomena Freitas
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Life is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • biopolymer
  • polysaccharides
  • polyamides
  • polyhydroxyalkanoates

Related Special Issue

Published Papers (6 papers)

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Research

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14 pages, 2490 KiB  
Article
Valorization of Brewery Waste through Polyhydroxyalkanoates Production Supported by a Metabolic Specialized Microbiome
by Mónica Carvalheira, Catarina L. Amorim, Ana Catarina Oliveira, Eliana C. Guarda, Eunice Costa, Margarida Ribau Teixeira, Paula M. L. Castro, Anouk F. Duque and Maria A. M. Reis
Life 2022, 12(9), 1347; https://doi.org/10.3390/life12091347 - 30 Aug 2022
Cited by 4 | Viewed by 1894
Abstract
Raw brewers’ spent grain (BSG), a by-product of beer production and produced at a large scale, presents a composition that has been shown to have potential as feedstock for several biological processes, such as polyhydroxyalkanoates (PHAs) production. Although the high interest in the [...] Read more.
Raw brewers’ spent grain (BSG), a by-product of beer production and produced at a large scale, presents a composition that has been shown to have potential as feedstock for several biological processes, such as polyhydroxyalkanoates (PHAs) production. Although the high interest in the PHA production from waste, the bioconversion of BSG into PHA using microbial mixed cultures (MMC) has not yet been explored. This study explored the feasibility to produce PHA from BSG through the enrichment of a mixed microbial culture in PHA-storing organisms. The increase in organic loading rate (OLR) was shown to have only a slight influence on the process performance, although a high selectivity in PHA-storing microorganisms accumulation was reached. The culture was enriched on various PHA-storing microorganisms, such as bacteria belonging to the Meganema, Carnobacterium, Leucobacter, and Paracocccus genera. The enrichment process led to specialization of the microbiome, but the high diversity in PHA-storing microorganisms could have contributed to the process stability and efficiency, allowing for achieving a maximum PHA content of 35.2 ± 5.5 wt.% (VSS basis) and a yield of 0.61 ± 0.09 CmmolPHA/CmmolVFA in the accumulation assays. Overall, the production of PHA from fermented BSG is a feasible process confirming the valorization potential of the feedstock through the production of added-value products. Full article
(This article belongs to the Special Issue Microbial Biopolymers: From Synthesis to Properties and Applications)
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11 pages, 510 KiB  
Article
Influence of Dissolved Oxygen Level on Chitin–Glucan Complex and Mannans Production by the Yeast Pichia pastoris
by Inês Farinha, Sílvia Baptista, Maria A. M. Reis and Filomena Freitas
Life 2022, 12(2), 161; https://doi.org/10.3390/life12020161 - 21 Jan 2022
Cited by 3 | Viewed by 2685
Abstract
The yeast Pichia pastoris was cultivated under different dissolved oxygen (DO) levels (5, 15, 30 and 50% of the air saturation) to evaluate its impact on the production of the cell-wall polysaccharide chitin–glucan complex (CGC) and mannans. Decreasing the DO level from 50 [...] Read more.
The yeast Pichia pastoris was cultivated under different dissolved oxygen (DO) levels (5, 15, 30 and 50% of the air saturation) to evaluate its impact on the production of the cell-wall polysaccharide chitin–glucan complex (CGC) and mannans. Decreasing the DO level from 50 to 15% had no significant impact on cell growth but substrate conversion into biomass was improved. Under such conditions, a mannans content in the biomass of 22 wt% was reached, while the CGC content in the biomass was improved from 15 to 18 wt%, confirming that the DO level also impacted on P. pastoris cell-wall composition. Overall mannans and CGC volumetric productivity values of 10.69 and 8.67 g/(L. day) were reached, respectively. On the other hand, the polymers’ composition was not significantly affected by decreasing the DO level. These results demonstrated that considerable energy savings can be made in the polysaccharide production process by reducing the DO level during cultivation of P. pastoris by improving the overall polymers’ productivity without altering their composition. This has impact on the polysaccharide production costs, which is of considerable relevance for process scale-up and products’ commercialization. Full article
(This article belongs to the Special Issue Microbial Biopolymers: From Synthesis to Properties and Applications)
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15 pages, 2219 KiB  
Article
Tyrosine Kinase Self-Phosphorylation Controls Exopolysaccharide Biosynthesis in Gluconacetobacter diazotrophicus Strain Pal5
by Katyanne Wanderley, Dayse Sousa, Gabriel Silva, Josemir Maia, Maria Silva, Marcia Vidal, José Baldani and Carlos Meneses
Life 2021, 11(11), 1231; https://doi.org/10.3390/life11111231 - 13 Nov 2021
Cited by 1 | Viewed by 1667
Abstract
The biosynthesis of exopolysaccharides (EPSs) is essential for endophytic bacterial colonisation in plants bacause this exopolymer both protects bacterial cells against the defence and oxidative systems of plants and acts on the plant colonisation mechanism in Gluconacetobacter diazotrophicus. The pathway involved in [...] Read more.
The biosynthesis of exopolysaccharides (EPSs) is essential for endophytic bacterial colonisation in plants bacause this exopolymer both protects bacterial cells against the defence and oxidative systems of plants and acts on the plant colonisation mechanism in Gluconacetobacter diazotrophicus. The pathway involved in the biosynthesis of bacterial EPS has not been fully elucidated, and several areas related to its molecular regulation mechanisms are still lacking. G. diazotrophicus relies heavily on EPS for survival indirectly by protecting plants from pathogen attack as well as for endophytic maintenance and adhesion in plant tissues. Here, we report that EPS from G. diazotrophicus strain Pal5 is a signal polymer that controls its own biosynthesis. EPS production depends on a bacterial tyrosine (BY) kinase (Wzc) that consists of a component that is able to phosphorylate a glycosyltranferase or to self-phosphorylate. EPS interacts with the extracellular domain of Wzc, which regulates kinase activity. In G. diazotrophicus strains that are deficient in EPS production, the Wzc is rendered inoperative by self-phosphorylation. The presence of EPS promotes the phosphorylation of a glycosyltransferase in the pathway, thus producing EPS. Wzc-mediated self-regulation is an attribute for the control of exopolysaccharide biosynthesis in G. diazotrophicus. Full article
(This article belongs to the Special Issue Microbial Biopolymers: From Synthesis to Properties and Applications)
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17 pages, 4735 KiB  
Article
Preparation and Characterization of Porous Scaffolds Based on Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
by Asiyah Esmail, João R. Pereira, Chantal Sevrin, Christian Grandfils, Ugur Deneb Menda, Elvira Fortunato, Abel Oliva and Filomena Freitas
Life 2021, 11(9), 935; https://doi.org/10.3390/life11090935 - 08 Sep 2021
Cited by 7 | Viewed by 2837
Abstract
Poly(hydroxyalkanoates) (PHAs) with different material properties, namely, the homopolymer poly(3-hydroxybutyrate), P(3HB), and the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate, P(3HB-co-3HV), with a 3HV of 25 wt.%, were used for the preparation of porous biopolymeric scaffolds. Solvent casting with particulate leaching (SCPL) and emulsion [...] Read more.
Poly(hydroxyalkanoates) (PHAs) with different material properties, namely, the homopolymer poly(3-hydroxybutyrate), P(3HB), and the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate, P(3HB-co-3HV), with a 3HV of 25 wt.%, were used for the preparation of porous biopolymeric scaffolds. Solvent casting with particulate leaching (SCPL) and emulsion templating were evaluated to process these biopolymers in porous scaffolds. SCPL scaffolds were highly hydrophilic (>170% swelling in water) but fragile, probably due to the increase of the polymer’s polydispersity index and its high porosity (>50%). In contrast, the emulsion templating technique resulted in scaffolds with a good compromise between porosity (27–49% porosity) and hydrophilicity (>30% water swelling) and without impairing their mechanical properties (3.18–3.35 MPa tensile strength and 0.07–0.11 MPa Young’s Modulus). These specifications are in the same range compared to other polymer-based scaffolds developed for tissue engineering. P(3HB-co-3HV) displayed the best overall properties, namely, lower crystallinity (11.3%) and higher flexibility (14.8% elongation at break. Our findings highlight the potency of our natural biopolyesters for the future development of novel porous scaffolds in tissue engineering, thanks also to their safety and biodegradability. Full article
(This article belongs to the Special Issue Microbial Biopolymers: From Synthesis to Properties and Applications)
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Review

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19 pages, 1366 KiB  
Review
Post-Transcriptional Control in the Regulation of Polyhydroxyalkanoates Synthesis
by Alexandra Peregrina, João Martins-Lourenço, Filomena Freitas, Maria A. M. Reis and Cecília M. Arraiano
Life 2021, 11(8), 853; https://doi.org/10.3390/life11080853 - 20 Aug 2021
Cited by 2 | Viewed by 3077
Abstract
The large production of non-degradable petrol-based plastics has become a major global issue due to its environmental pollution. Biopolymers produced by microorganisms such as polyhydroxyalkanoates (PHAs) are gaining potential as a sustainable alternative, but the high cost associated with their industrial production has [...] Read more.
The large production of non-degradable petrol-based plastics has become a major global issue due to its environmental pollution. Biopolymers produced by microorganisms such as polyhydroxyalkanoates (PHAs) are gaining potential as a sustainable alternative, but the high cost associated with their industrial production has been a limiting factor. Post-transcriptional regulation is a key step to control gene expression in changing environments and has been reported to play a major role in numerous cellular processes. However, limited reports are available concerning the regulation of PHA accumulation in bacteria, and many essential regulatory factors still need to be identified. Here, we review studies where the synthesis of PHA has been reported to be regulated at the post-transcriptional level, and we analyze the RNA-mediated networks involved. Finally, we discuss the forthcoming research on riboregulation, synthetic, and metabolic engineering which could lead to improved strategies for PHAs synthesis in industrial production, thereby reducing the costs currently associated with this procedure. Full article
(This article belongs to the Special Issue Microbial Biopolymers: From Synthesis to Properties and Applications)
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25 pages, 2947 KiB  
Review
Recent Advances in the Biosynthesis of Polyhydroxyalkanoates from Lignocellulosic Feedstocks
by Sevakumaran Vigneswari, Muhammad Shahrul Md Noor, Tan Suet May Amelia, Karthnee Balakrishnan, Azila Adnan, Kesaven Bhubalan, Al-Ashraf Abdullah Amirul and Seeram Ramakrishna
Life 2021, 11(8), 807; https://doi.org/10.3390/life11080807 - 10 Aug 2021
Cited by 38 | Viewed by 5589
Abstract
Polyhydroxyalkanoates (PHA) are biodegradable polymers that are considered able to replace synthetic plastic because their biochemical characteristics are in some cases the same as other biodegradable polymers. However, due to the disadvantages of costly and non-renewable carbon sources, the production of PHA has [...] Read more.
Polyhydroxyalkanoates (PHA) are biodegradable polymers that are considered able to replace synthetic plastic because their biochemical characteristics are in some cases the same as other biodegradable polymers. However, due to the disadvantages of costly and non-renewable carbon sources, the production of PHA has been lower in the industrial sector against conventional plastics. At the same time, first-generation sugar-based cultivated feedstocks as substrates for PHA production threatens food security and considerably require other resources such as land and energy. Therefore, attempts have been made in pursuit of suitable sustainable and affordable sources of carbon to reduce production costs. Thus, in this review, we highlight utilising waste lignocellulosic feedstocks (LF) as a renewable and inexpensive carbon source to produce PHA. These waste feedstocks, second-generation plant lignocellulosic biomass, such as maize stoves, dedicated energy crops, rice straws, wood chips, are commonly available renewable biomass sources with a steady supply of about 150 billion tonnes per year of global yield. The generation of PHA from lignocellulose is still in its infancy, hence more screening of lignocellulosic materials and improvements in downstream processing and substrate pre-treatment are needed in the future to further advance the biopolymer sector. Full article
(This article belongs to the Special Issue Microbial Biopolymers: From Synthesis to Properties and Applications)
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