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Polymers
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Microbial Biopolymers: Trends in Synthesis, Modification, and Applications
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Microbial Biopolymers: Trends in Synthesis, Modification, and Applications

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Biomacromolecules, Biobased and Biodegradable Polymers".

Deadline for manuscript submissions: closed (5 March 2023) | Viewed by 33157

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Dr. Shashi Kant Bhatia

E-Mail Website
Guest Editor
Department of Biological Engineering, Konkuk University, Seoul 05029, Republic of Korea
Interests: biocatalysis and enzyme engineering; biofuel; biomaterial; biochemical engineering; antibiotics; metabolic engineering; glycosylation; bioencapsulation; mutagenesis; protein purification; molecular biology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microbes can act as a factory for the conversion of a variety of carbon and nitrogen sources into diverse kinds of intracellular and extracellular biopolymers including polyhydroxyalkanoates, polysaccharides, polyamides, polyphosphates, etc. These biopolymers have a diverse biological role in a microbial system such as reserve food material, pathogenicity, biofilm formation, and protection against adverse environmental conditions. Biopolymers have different chemical and morphological properties that make them suitable for industrial, environmental, and medical applications. Recent advances in molecular biology, transcriptomics, metabolomics techniques have improved the understanding related to mechanisms and regulations involved in biopolymer synthesis. A microbial system can be easily engineered and cultured under controlled conditions to produce desired polymers. Biopolymers produced by microbial systems are rich in various functional groups which can be exploited further to modify the polymers for a variety of applications. Biopolymer's production cost is the main challenge for its applicability at a commercial scale. Researchers are working on the utilization of diverse kinds of organic wastes such as lignocellulosic waste, municipal waste, whey, paper and pulp industry waste, etc. as feedstock for microbial fermentation. Biopolymer production from the microbial system is a clean and green approach and has recently become a hot topic around the globe and it is considered as a possible way to deal with plastic-based wastes and has tremendous applications in the biotechnology sector. Keeping in view the recent advances in microbial biopolymer production technologies, modification, and applications this special issue will include a series of review and research articles covering the following issue, but not limited to:

  • Strategy for selection of novel biopolymer producer and improvement of existing microbes using a genetic engineering approach.
  • Recent technological advancements in improved biopolymer production using pure culture or mixed culture.
  • Utilize cheap and unconventional feedstocks for biopolymer production.
  • Reactor design and improvements of the upstream and downstream process.
  • Modification and fabrication of biopolymers for diverse applications
  • Applications of biopolymers in health, food, environment, and other areas.
  • Biodegradation of polymers
  • Techno-economic analysis of biopolymer production.

Dr. Shashi Kant Bhatia
Guest Editor

Manuscript Submission Information

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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. Polymers is an international peer-reviewed open access semimonthly 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 2700 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
  • polyhydroxyalkanoates
  • exopolysaccharides
  • polyamides
  • biodegradation
  • techno-economic analysis

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Published Papers (15 papers)

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Editorial

Jump to: Research, Review

4 pages, 554 KiB  
Editorial
Microbial Biopolymers: Trends in Synthesis, Modification, and Applications
by Shashi Kant Bhatia
Polymers 2023, 15(6), 1364; https://doi.org/10.3390/polym15061364 - 09 Mar 2023
Cited by 1 | Viewed by 1366
Abstract
Microbes can act as a factory for the conversion of a variety of carbon and nitrogen sources into diverse kinds of intracellular and extracellular biopolymers, including polyhydroxyalkanoates (PHA) and exopolysaccharides (EPS), under different stress conditions [...] Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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Research

Jump to: Editorial, Review

16 pages, 1282 KiB  
Article
Phormidium ambiguum and Leptolyngbya ohadii Exopolysaccharides under Low Water Availability
by Isabela C. Moia, Sara B. Pereira, Paola Domizio, Roberto De Philippis and Alessandra Adessi
Polymers 2023, 15(8), 1889; https://doi.org/10.3390/polym15081889 - 14 Apr 2023
Cited by 1 | Viewed by 1513
Abstract
Cyanobacteria can cope with various environmental stressors, due to the excretion of exopolysaccharides (EPS). However, little is known about how the composition of these polymers may change according to water availability. This work aimed at characterizing the EPS of Phormidium ambiguum (Oscillatoriales; Oscillatoriaceae) [...] Read more.
Cyanobacteria can cope with various environmental stressors, due to the excretion of exopolysaccharides (EPS). However, little is known about how the composition of these polymers may change according to water availability. This work aimed at characterizing the EPS of Phormidium ambiguum (Oscillatoriales; Oscillatoriaceae) and Leptolyngbya ohadii (Pseudanabaenales; Leptolyngbyaceae), when grown as biocrusts and biofilms, subject to water deprivation. The following EPS fractions were quantified and characterized: soluble (loosely bound, LB) and condensed (tightly bound, TB) for biocrusts, released (RPS), and sheathed in P. ambiguum and glycocalyx (G-EPS) in L. ohadii for biofilms. For both cyanobacteria upon water deprivation, glucose was the main monosaccharide present and the amount of TB-EPS resulted was significantly higher, confirming its importance in these soil-based formations. Different profiles of monosaccharides composing the EPSs were observed, as for example the higher concentration of deoxysugars observed in biocrusts compared to biofilms, demonstrating the plasticity of the cells to modify EPS composition as a response to different stresses. For both cyanobacteria, both in biofilms and biocrusts, water deprivation induced the production of simpler carbohydrates, with an increased dominance index of the composing monosaccharides. The results obtained are useful in understanding how these very relevant cyanobacterial species are sensitively modifying the EPS secreted when subject to water deprivation and could lead to consider them as suitable inoculants in degraded soils. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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22 pages, 3345 KiB  
Article
Production and Characterisation of an Exopolysaccharide by Bacillus amyloliquefaciens: Biotechnological Applications
by Enrique Sánchez-León, Elisa Huang-Lin, Ricardo Amils and Concepción Abrusci
Polymers 2023, 15(6), 1550; https://doi.org/10.3390/polym15061550 - 21 Mar 2023
Cited by 1 | Viewed by 1936
Abstract
The Bacillus amyloliquefaciens RT7 strain was isolated from an extreme acidic environment and identified. The biodegradation capabilities of the strain using different carbon sources (glucose, oleic acid, Tween 80, PEG 200, and the combination of glucose–Tween 80) were evaluated via an indirect impedance [...] Read more.
The Bacillus amyloliquefaciens RT7 strain was isolated from an extreme acidic environment and identified. The biodegradation capabilities of the strain using different carbon sources (glucose, oleic acid, Tween 80, PEG 200, and the combination of glucose–Tween 80) were evaluated via an indirect impedance technique. The glucose–Tween 80 combination was further studied using nuclear magnetic resonance (NMR). The exopolysaccharide (EPSRT7) that had been produced with the strain when biodegrading glucose–Tween 80 was isolated and characterised using different techniques (GC–MS, HPLC/MSMS, ATR–FTIR, TGA, and DSC), and its molecular weight was estimated. The results show that the average molecular weight of EPSRT7 was approximately 7.0794 × 104 Da and a heteropolysaccharide composed of mannose, glucose, galactose, and xylose (molar ratio, 1:0.5:0.1:0.1) with good thermostability. EPSRT7 showed good emulsifying activity against different natural oils and hydrocarbons at high concentrations (2 mg/mL) and at the studied pH range (3.1–7.2). It also presented good emulsifying activity compared to that of commercial emulsifiers. Lastly, EPSRT7 showed antioxidant capacity for different free radicals, a lack of cytotoxicity, and antioxidant activity at the cellular level. EPSRT7 has promising applications in bioremediation processes and other industrial applications. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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16 pages, 33193 KiB  
Article
Identification of a Thermostable Levansucrase from Pseudomonas orientalis That Allows Unique Product Specificity at Different Temperatures
by Cuie Guang, Xiaoqi Zhang, Dawei Ni, Wenli Zhang, Wei Xu and Wanmeng Mu
Polymers 2023, 15(6), 1435; https://doi.org/10.3390/polym15061435 - 14 Mar 2023
Cited by 2 | Viewed by 1238
Abstract
The biological production of levan by levansucrase (LS, EC 2.4.1.10) has aroused great interest in the past few years. Previously, we identified a thermostable levansucrase from Celerinatantimonas diazotrophica (Cedi-LS). A novel thermostable LS from Pseudomonas orientalis (Psor-LS) was successfully screened using the Cedi-LS [...] Read more.
The biological production of levan by levansucrase (LS, EC 2.4.1.10) has aroused great interest in the past few years. Previously, we identified a thermostable levansucrase from Celerinatantimonas diazotrophica (Cedi-LS). A novel thermostable LS from Pseudomonas orientalis (Psor-LS) was successfully screened using the Cedi-LS template. The Psor-LS showed maximum activity at 65 °C, much higher than the other LSs. However, these two thermostable LSs showed significantly different product specificity. When the temperature was decreased from 65 to 35 °C, Cedi-LS tended to produce high-molecular-weight (HMW) levan. By contrast, Psor-LS prefers to generate fructooligosaccharides (FOSs, DP ≤ 16) rather than HMW levan under the same conditions. Notably, at 65 °C, Psor-LS would produce HMW levan with an average Mw of 1.4 × 106 Da, indicating that a high temperature might favor the accumulation of HMW levan. In summary, this study allows a thermostable LS suitable for HMW levan and levan-type FOSs production simultaneously. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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14 pages, 5434 KiB  
Article
Microbial Poly(hydroxybutyrate-co-hydroxyvalerate) Scaffold for Periodontal Tissue Engineering
by Seubsakul Phuegyod, Sasivimon Pramual, Nungnit Wattanavichean, Supasuda Assawajaruwan, Taweechai Amornsakchai, Panithi Sukho, Jisnuson Svasti, Rudee Surarit and Nuttawee Niamsiri
Polymers 2023, 15(4), 855; https://doi.org/10.3390/polym15040855 - 09 Feb 2023
Cited by 4 | Viewed by 1980
Abstract
In this study, we fabricated three dimensional (3D) porous scaffolds of poly(hydroxybutyrate-co-hydroxyvalerate) with 50% HV content. P(HB-50HV) was biosynthesized from bacteria Cupriavidus necator H16 and the in vitro proliferation of dental cells for tissue engineering application was evaluated. Comparisons were made with scaffolds [...] Read more.
In this study, we fabricated three dimensional (3D) porous scaffolds of poly(hydroxybutyrate-co-hydroxyvalerate) with 50% HV content. P(HB-50HV) was biosynthesized from bacteria Cupriavidus necator H16 and the in vitro proliferation of dental cells for tissue engineering application was evaluated. Comparisons were made with scaffolds prepared by poly(hydroxybutyrate) (PHB), poly(hydroxybutyrate-co-12%hydroxyvalerate) (P(HB-12HV)), and polycaprolactone (PCL). The water contact angle results indicated a hydrophobic character for all polymeric films. All fabricated scaffolds exhibited a high porosity of 90% with a sponge-like appearance. The P(HB-50HV) scaffolds were distinctively different in compressive modulus and was the material with the lowest stiffness among all scaffolds tested between the dry and wet conditions. The human gingival fibroblasts (HGFs) and periodontal ligament stem cells (PDLSCs) cultured onto the P(HB-50HV) scaffold adhered to the scaffold and exhibited the highest proliferation with a healthy morphology, demonstrating excellent cell compatibility with P(HB-50HV) scaffolds. These results indicate that the P(HB-50HV) scaffold could be applied as a biomaterial for periodontal tissue engineering and stem cell applications. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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16 pages, 2266 KiB  
Article
Two-Stage Bio-Hydrogen and Polyhydroxyalkanoate Production: Upcycling of Spent Coffee Grounds
by Beom-Jung Kang, Jong-Min Jeon, Shashi Kant Bhatia, Do-Hyung Kim, Yung-Hun Yang, Sangwon Jung and Jeong-Jun Yoon
Polymers 2023, 15(3), 681; https://doi.org/10.3390/polym15030681 - 29 Jan 2023
Cited by 15 | Viewed by 2864
Abstract
Coffee waste is an abundant biomass that can be converted into high value chemical products, and is used in various renewable biological processes. In this study, oil was extracted from spent coffee grounds (SCGs) and used for polyhydroxyalkanoate (PHA) production through Pseudomonas resinovorans [...] Read more.
Coffee waste is an abundant biomass that can be converted into high value chemical products, and is used in various renewable biological processes. In this study, oil was extracted from spent coffee grounds (SCGs) and used for polyhydroxyalkanoate (PHA) production through Pseudomonas resinovorans. The oil–extracted SCGs (OESCGs) were hydrolyzed and used for biohydrogen production through Clostridium butyricum DSM10702. The oil extraction yield through n–hexane was 14.4%, which accounted for 97% of the oil present in the SCGs. OESCG hydrolysate (OESCGH) had a sugar concentration of 32.26 g/L, which was 15.4% higher than that of the SCG hydrolysate (SCGH) (27.96 g/L). Hydrogen production using these substrates was 181.19 mL and 136.58 mL in OESCGH and SCGH media, respectively. The consumed sugar concentration was 6.77 g/L in OESCGH and 5.09 g/L in SCGH media. VFA production with OESCGH (3.58 g/L) increased by 40.9% compared with SCGH (2.54 g/L). In addition, in a fed–batch culture using the extracted oil, cell dry weight was 5.4 g/L, PHA was 1.6 g/L, and PHA contents were 29.5% at 24 h. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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15 pages, 3710 KiB  
Article
Finding of Novel Galactose Utilizing Halomonas sp. YK44 for Polyhydroxybutyrate (PHB) Production
by Hee Ju Jung, Su Hyun Kim, Do Hyun Cho, Byung Chan Kim, Shashi Kant Bhatia, Jongbok Lee, Jong-Min Jeon, Jeong-Jun Yoon and Yung-Hun Yang
Polymers 2022, 14(24), 5407; https://doi.org/10.3390/polym14245407 - 10 Dec 2022
Cited by 17 | Viewed by 2017
Abstract
Polyhydroxybutyrate (PHB) is a biodegradable bioplastic with potential applications as an alternative to petroleum-based plastics. However, efficient PHB production remains difficult. The main cost of PHB production is attributed to carbon sources; hence, finding inexpensive sources is important. Galactose is a possible substrate [...] Read more.
Polyhydroxybutyrate (PHB) is a biodegradable bioplastic with potential applications as an alternative to petroleum-based plastics. However, efficient PHB production remains difficult. The main cost of PHB production is attributed to carbon sources; hence, finding inexpensive sources is important. Galactose is a possible substrate for polyhydroxyalkanoate production as it is abundant in marine environments. Marine bacteria that produce PHB from galactose could be an effective resource that can be used for efficient PHB production. In this study, to identify a galactose utilizing PHB producer, we examined 16 Halomonas strains. We demonstrated that Halomonas cerina (Halomonas sp. YK44) has the highest growth and PHB production using a culture media containing 2% galactose, final 4% NaCl, and 0.1% yeast extract. These culture conditions yielded 8.98 g/L PHB (78.1% PHB content (w/w)). When galactose-containing red algae (Eucheuma spinosum) hydrolysates were used as a carbon source, 5.2 g/L PHB was produced with 1.425% galactose after treatment with activated carbon. Since high salt conditions can be used to avoid sterilization, we examined whether Halomonas sp. YK44 could produce PHB in non-sterilized conditions. Culture media in these conditions yielded 72.41% PHB content. Thus, Halomonas sp. YK44 is robust against contamination, allowing for long-term culture and economical PHB production. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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14 pages, 4391 KiB  
Article
Finding a Benign Plasticizer to Enhance the Microbial Degradation of Polyhydroxybutyrate (PHB) Evaluated by PHB Degrader Microbulbifer sp. SOL66
by Jang Yeon Cho, Su Hyun Kim, Hee Ju Jung, Do Hyun Cho, Byung Chan Kim, Shashi Kant Bhatia, Jungoh Ahn, Jong-Min Jeon, Jeong-Jun Yoon, Jongbok Lee and Yung-Hun Yang
Polymers 2022, 14(17), 3625; https://doi.org/10.3390/polym14173625 - 01 Sep 2022
Cited by 14 | Viewed by 1791
Abstract
As a biodegradable plastic, polyhydroxybutyrate (PHB) has relatively poor mechanical properties, preventing its wider use. Various plasticizers have been studied to improve the mechanical properties of PHB; however, due to the slow degradation speed in the soil environment and lack of evaluation methods, [...] Read more.
As a biodegradable plastic, polyhydroxybutyrate (PHB) has relatively poor mechanical properties, preventing its wider use. Various plasticizers have been studied to improve the mechanical properties of PHB; however, due to the slow degradation speed in the soil environment and lack of evaluation methods, studies on the degradation of PHB with plasticizers are rarely reported. In this study, by applying Microbulbifer sp. SOL66, which is able to degrade PHB very quickly, a benign plasticizer was evaluated with good properties and good degradability, not inhibiting microbial activities. Eight different plasticizers were applied with PHB and Microbulbifer sp. SOL66, PHB film containing 10% and 20% tributyl citrate showed significant biodegradability of PHB. It was confirmed that tributyl citrate could increase the speed of PHB degradation by Microbulbifer sp. SOL66 by 88% at 1 day, although the degree of degradation was similar after 3 days with and without tributyl citrate. By the analysis of microbial degradation, physical, chemical, and mechanical properties, tributyl citrate was shown not only to improve physical, chemical, and mechanical properties but also the speed of microbial degradation. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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16 pages, 1862 KiB  
Article
The Hyperproduction of Polyhydroxybutyrate Using Bacillus mycoides ICRI89 through Enzymatic Hydrolysis of Affordable Cardboard
by Fady Abdelmalek, Alexander Steinbüchel and Marian Rofeal
Polymers 2022, 14(14), 2810; https://doi.org/10.3390/polym14142810 - 10 Jul 2022
Cited by 12 | Viewed by 2760
Abstract
Bioplastics are contemplated as remarkable substitutes for conventional plastics to accommodate green technological advancements. However, their industrial production has not been fully implemented owing to the cost of carbon resources. From another perspective, valorizing different paper mill wastes has become a prominent research [...] Read more.
Bioplastics are contemplated as remarkable substitutes for conventional plastics to accommodate green technological advancements. However, their industrial production has not been fully implemented owing to the cost of carbon resources. From another perspective, valorizing different paper mill wastes has become a prominent research topic. These materials may serve as an affording sustainable feedstock for bioplastic production. Adjustment of cardboard waste hydrolysate as suitable fermentation media for production of bacterial polyhydroxyalkanoates (PHAs) has been investigated. Cardboard samples were defibered and dried before enzymatic hydrolysis. The enzymatic degradation of commercial cellulase was monitored over 15 days. Interestingly, 18.2 ± 0.2 g/L glucose yield was obtained from 50 g cardboard samples using a 1.5% (v/v) enzyme concentration. The samples exhibited maximum weight loss values of 69–73%. Meanwhile, five soil samples were collected from local sites in Lodz, Poland. A total of 31 bacterial isolates were screened and cultured on Nile blue plates. Analysis of the 16S rRNA gene sequence of the most potent producer revealed 100% similarity to Bacillus mycoides. Cardboard hydrolysates whole medium, modified MSM with cardboard hydrolysate and nitrogen depleted MSM with cardboard hydrolysate were utilized for PHA production, followed by PHA productivity and cell dry weight (CDW) estimation compared to glucose as a standard carbon source. An impressive PHA accumulation of 56% CDW was attained when the waste hydrolysate was used as a carbon source. FTIR and NMR analysis of the isolated PHA indicated that functional groups of the polymer were related to PHB (polyhydroxybutyrate). Thermal analysis demonstrates that PHB and PHB-CB (PHB produced from cardboard hydrolysate) have degradation temperatures of 380 and 369 °C, respectively, which reflect the high thermal stability and heat resistance compared to the same properties for a standard polymer. This is the first demonstration of full saccharification of corrugated cardboard paper waste for high-level production of PHA. In addition, the attained PHB productivity is one of the highest levels achieved from a real lignocellulosic waste. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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11 pages, 1676 KiB  
Article
Bioconversion of Mixed Alkanes to Polyhydroxyalkanoate by Pseudomonas resinovornas: Upcycling of Pyrolysis Oil from Waste-Plastic
by Jong-Min Jeon, So-Jin Park, Ye-Seung Son, Yung-Hun Yang and Jeong-Jun Yoon
Polymers 2022, 14(13), 2624; https://doi.org/10.3390/polym14132624 - 28 Jun 2022
Cited by 6 | Viewed by 1547
Abstract
Polyhydroxyalkanoate (PHA) is a biodegradable plastic that can be used to replace petroleum-based plastic. In addition, as a medium-chain-length PHA (mcl-PHA), it can be used to provide elastomeric properties in specific applications. Because of these characteristics, recently, there has been much research on [...] Read more.
Polyhydroxyalkanoate (PHA) is a biodegradable plastic that can be used to replace petroleum-based plastic. In addition, as a medium-chain-length PHA (mcl-PHA), it can be used to provide elastomeric properties in specific applications. Because of these characteristics, recently, there has been much research on mcl-PHA production using inexpensive biomass materials as substrates. In this study, mcl-PHA producers were screened using alkanes (n-octane, n-decane, and n-dodecane) as sources of carbon. The amount of PHA produced by Pseudomonas resinovorans using sole n-octane, n-decane, or n-dodecane was 0.48 g/L, 0.27 g/L, or 0.07 g/L, respectively, while that produced using mixed alkane was 0.74 g/L. As a larger amount of PHA was produced using mixed alkane compared with sole alkane, a statistical mixture analysis was used to determine the optimal ratio of alkanes in the mixture. The optimal ratio predicted by the analysis was a medium with 9.15% n-octane, 6.44% n-decane, and 4.29% n-dodecane. In addition, through several concentration-specific experiments, the optimum concentrations of nitrogen and phosphorus for cell growth and maximum PHA production were determined as 0.05% and 1.0%, respectively. Finally, under the determined optimal conditions, 2.1 g/L of mcl-PHA and 60% PHA content were obtained using P. resinovorans in a 7 L fermenter. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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22 pages, 2962 KiB  
Article
Emulgels Containing Perilla frutescens Seed Oil, Moringa oleifera Seed Oil, and Mixed Seed Oil: Microemulsion and Safety Assessment
by Prakairat Tunit, Chuda Chittasupho, Kusuma Sriyakul, Parunkul Tungsuruthai, Panlop Chakkavittumrong, Kesara Na-Bangchang and Somboon Kietinun
Polymers 2022, 14(12), 2348; https://doi.org/10.3390/polym14122348 - 09 Jun 2022
Cited by 3 | Viewed by 2166
Abstract
P. frutescens seed oil and M. oleifera seed oil consist of fatty acids and sterols that are beneficial for skin. Mixing of these oils at 1:1 ratio has shown to increase antioxidant activity of oils. This study aims to formulate emulgels containing microemulsions [...] Read more.
P. frutescens seed oil and M. oleifera seed oil consist of fatty acids and sterols that are beneficial for skin. Mixing of these oils at 1:1 ratio has shown to increase antioxidant activity of oils. This study aims to formulate emulgels containing microemulsions of P. frutescens seed oil, M. oleifera seed oil, and mixed P. frutescens and M. oleifera seed oils. The chemical constituents of P. frutescens seed oil, M. oleifera seed oil, and mixed seed oil are analyzed by gas chromatography/mass spectrometry (GC/MS). The microemulsions are formulated by a phase titration method and characterized for the droplet size, polydispersity index, and zeta potential value using a dynamic light scattering technique. The physical and chemical stability of the microemulsions are investigated using a rheometer and UV-Visible spectrophotometer, respectively. The safety of microemulsion is evaluated on PBMC and human subjects. Emulgels containing three different types of microemulsion are formulated. The results show that P. frutescens seed oil is mainly composed of alpha-linolenic acid, linoleic acid, and oleic acid, whereas M. oleifera seed oil contains a high proportion of oleic acid. Mixed seed oil contains a comparable amount of alpha-linolenic acid and oleic acid. All types of oils are composed of β-sitosterol as the major plant sterol. Microemulsions of all types of oils are successfully prepared by using Tween 80 as a surfactant due to the largest transparent region of pseudoternary phase diagram. The size, polydispersity index, and zeta potential values of all types of microemulsion are in the acceptable range upon storage at 30 °C for 1 month. Microemulsions exhibit pseudoplastic flow behavior. The percent of remaining oils in all types of microemulsion is more than 90% after storage at 30 °C for 1 month. Emulgels containing three types of microemulsions exhibit good characteristics and no change in viscosity after storage at 4, 30, and 45 °C for 1 month. The safety results reveal that three types of microemulsion do not induce cytotoxicity to PBMC nor induce skin irritation and allergic reactions. Emulgels containing microemulsions developed in this study can be used to safely deliver P. frutescens seed oil, M. oleifera seed oil, and mixed seed oil to human skin. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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13 pages, 4297 KiB  
Article
Supercritical CO2 Foaming of Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)
by Tao Zhang, Yunjae Jang, Eunhye Lee, Sooan Shin and Ho-Jong Kang
Polymers 2022, 14(10), 2018; https://doi.org/10.3390/polym14102018 - 15 May 2022
Cited by 5 | Viewed by 2090
Abstract
The supercritical carbon dioxide foaming characteristics of the biodegradable polymer poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) are studied for environmentally friendly packaging materials. The effect of the 4HB composition of the P(3HB-co-4HB) copolymers on the foaming conditions such as pressure and temperature is [...] Read more.
The supercritical carbon dioxide foaming characteristics of the biodegradable polymer poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) are studied for environmentally friendly packaging materials. The effect of the 4HB composition of the P(3HB-co-4HB) copolymers on the foaming conditions such as pressure and temperature is studied and the density and the expansion ratio of the resulting P(3HB-co-4HB) foam are together evaluated. The increase in the 4HB content reduces the crystallinity and tan δ value of P(3HB-co-4HB) required for the growth of the foam cells. Therefore, the foaming temperature needs to be lower to retain a suitable tan δ value of P(3HB-co-4HB) for foaming. It was found that P(3HB-co-4HB) with less crystallinity showed better formability and cell uniformity. However, foaming is not possible regardless of the foaming temperature when the 4HB content of P(3HB-co-4HB) is over 50%, due to the high tan δ value. A lower foam density and higher expansion ratio can be obtained with crystalline P(3HB-co-4HB) of low 4HB content, compared with non-crystalline P(3HB-co-4HB) of high 4HB content. The expansion ratio of P(3HB-co-4HB) foams can be increased slightly by using a chain extender, due to the lowing of crystallinity and tan δ. This is most effective in the case of P(3HB-co-4HB), whose 4HB content is 16%. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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16 pages, 3490 KiB  
Article
Combination of Hypotonic Lysis and Application of Detergent for Isolation of Polyhydroxyalkanoates from Extremophiles
by Ivana Novackova, Xenie Kourilova, Katerina Mrazova, Petr Sedlacek, Michal Kalina, Vladislav Krzyzanek, Martin Koller and Stanislav Obruca
Polymers 2022, 14(9), 1761; https://doi.org/10.3390/polym14091761 - 26 Apr 2022
Cited by 5 | Viewed by 2205
Abstract
Production of polyhydroxyalkanoates (PHA), microbial biopolyesters, employing extremophilic microorganisms is a very promising concept relying on robustness of such organisms against microbial contamination, which provides numerous economic and technological benefits. In this work, we took advantage of the natural susceptibility of halophilic and [...] Read more.
Production of polyhydroxyalkanoates (PHA), microbial biopolyesters, employing extremophilic microorganisms is a very promising concept relying on robustness of such organisms against microbial contamination, which provides numerous economic and technological benefits. In this work, we took advantage of the natural susceptibility of halophilic and thermophilic PHA producers to hypotonic lysis and we developed a simple and robust approach enabling effective isolation of PHA materials from microbial cells. The method is based on the exposition of microbial cells to hypotonic conditions induced by the diluted solution of sodium dodecyl sulfate (SDS) at elevated temperatures. Such conditions lead to disruption of the cells and release of PHA granules. Moreover, SDS, apart from its cell-disruptive function, also solubilizes hydrophobic components, which would otherwise contaminate PHA materials. The purity of obtained materials, as well as the yields of recovery, reach high values (values of purity higher than 99 wt.%, yields close to 1). Furthermore, we also focused on the removal of SDS from wastewater. The simple, inexpensive, and safe technique is based on the precipitation of SDS in the presence of KCl. The precipitate can be simply removed by decantation or centrifugation. Moreover, there is also the possibility to regenerate the SDS, which would substantially improve the economic feasibility of the process. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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13 pages, 3745 KiB  
Article
The Modification of Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) by Melt Blending
by Minki Jo, Yunjae Jang, Eunhye Lee, Sooan Shin and Ho-Jong Kang
Polymers 2022, 14(9), 1725; https://doi.org/10.3390/polym14091725 - 23 Apr 2022
Cited by 5 | Viewed by 1691
Abstract
Crystalline and noncrystalline poly(3-hyroxybutylate-co-4-hyroxybutylate) (P(3HB-co-4HB)) were melt blended to obtain mixtures of P(3HB-co-4HB) copolymers. The mixtures and P(3HB-co-4HB) copolymers of different 4HB contents were compared to study the effect of 4HB content on the properties of the copolymers and mixtures. P(3HB-co-4HB) copolymer mixtures, [...] Read more.
Crystalline and noncrystalline poly(3-hyroxybutylate-co-4-hyroxybutylate) (P(3HB-co-4HB)) were melt blended to obtain mixtures of P(3HB-co-4HB) copolymers. The mixtures and P(3HB-co-4HB) copolymers of different 4HB contents were compared to study the effect of 4HB content on the properties of the copolymers and mixtures. P(3HB-co-4HB) copolymer mixtures, having various 4HB content, have been successfully made by melt blending instead of bacterial biosynthesis. In the case of copolymers, they were noncrystalline when the 4HB content was over 16%, while the P(3HB-co-4HB) mixtures at the same 4HB content were crystalline. The mixtures had a higher glass transition temperature, suggesting that their chain mobility is relatively low compared with the copolymer having the same 4HB content. Due to this effect, the mixture is expected to have a higher melt viscosity and a lower loss tangent to exhibit better melt processing properties. The mechanical properties of the mixtures show a similar behavior to the copolymers in that the tensile strength and the modulus decreases and elongation at the break increases with an increase in the 4HB content. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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Review

Jump to: Editorial, Research

32 pages, 2540 KiB  
Review
Microbial Exopolysaccharide Composites in Biomedicine and Healthcare: Trends and Advances
by Vishal Ahuja, Arvind Kumar Bhatt, J. Rajesh Banu, Vinod Kumar, Gopalakrishnan Kumar, Yung-Hun Yang and Shashi Kant Bhatia
Polymers 2023, 15(7), 1801; https://doi.org/10.3390/polym15071801 - 06 Apr 2023
Cited by 14 | Viewed by 4385
Abstract
Microbial exopolysaccharides (EPSs), e.g., xanthan, dextran, gellan, curdlan, etc., have significant applications in several industries (pharma, food, textiles, petroleum, etc.) due to their biocompatibility, nontoxicity, and functional characteristics. However, biodegradability, poor cell adhesion, mineralization, and lower enzyme activity are some other factors that [...] Read more.
Microbial exopolysaccharides (EPSs), e.g., xanthan, dextran, gellan, curdlan, etc., have significant applications in several industries (pharma, food, textiles, petroleum, etc.) due to their biocompatibility, nontoxicity, and functional characteristics. However, biodegradability, poor cell adhesion, mineralization, and lower enzyme activity are some other factors that might hinder commercial applications in healthcare practices. Some EPSs lack biological activities that make them prone to degradation in ex vivo, as well as in vivo environments. The blending of EPSs with other natural and synthetic polymers can improve the structural, functional, and physiological characteristics, and make the composites suitable for a diverse range of applications. In comparison to EPS, composites have more mechanical strength, porosity, and stress-bearing capacity, along with a higher cell adhesion rate, and mineralization that is required for tissue engineering. Composites have a better possibility for biomedical and healthcare applications and are used for 2D and 3D scaffold fabrication, drug carrying and delivery, wound healing, tissue regeneration, and engineering. However, the commercialization of these products still needs in-depth research, considering commercial aspects such as stability within ex vivo and in vivo environments, the presence of biological fluids and enzymes, degradation profile, and interaction within living systems. The opportunities and potential applications are diverse, but more elaborative research is needed to address the challenges. In the current article, efforts have been made to summarize the recent advancements in applications of exopolysaccharide composites with natural and synthetic components, with special consideration of pharma and healthcare applications. Full article
(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications)
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