Crossing roads of plastic degradation and biomaterial production

Iako je već čitav vek prisutna u životima ljudi, plastika je i dalje jedan od najraznovrsnijih, najčešće proizvođenih i korišćenih materijala. Nekada najveća prednost plastike – izdržljivost – danas predstavlja veliki problem, jer je čini teško razgradivim materijalom koji se gomila u životnoj sredini [1]. Najčešće korišćen pristup za odlaganje ovog polimera je deponovanje, koje je pored ekološke pretnje ujedno i ekonomski izazov, jer se ovakvim odlaganjem plastike gubi uložena energija i mogućnost za ponovnu upotrebu materijala. Sa druge strane, biološki proces, zasnovan na enzimskoj razgradnji, pruža nekoliko prednosti: blage uslove, nizak utrošak energije, i odsustvo opasnih hemikalija [2]. Poseban značaj enzimske razgradnje plastike je što obezbeđuje niz metabolita - polaznih jedinjenja za proizvodnju novih vrednih polimera [3], čime se doprinosi uspostavljanju cirkularne ekonomije kada su u pitanju plastični materijali. Paralelno sa razvijanjem i unapređivanjem bioloških pristupa u razgradnji plastičnog otpada, istražuju se i ekološki prihvatljivi materijali koji bi mogli zameniti plastiku, kao što je biorazgradiv biopolimer - bakterijska nanoceluloza (Slika 1). Zahvaljujući svojim izvanrednim svojstvima kao što su mehanička čvrstoća, hidrofilnost, biokompatibilnost, obnovljivost i netoksičnost, bakterijska nanocelloza ima potencijal za primenu u različitim granama industrije [4]. Međutim, produkcija bakterijske nanoceluloze na industrijskoj skali je otežana visokom cenom medijuma za rast bakterija proizvođača. Iz tog razloga su svetska istraživanja poslednjih godina usmerena na optimizaciju produkcije bakterijske nanoceluloze korišćenjem različitih vrsta otpada [5].Knjiga izvoda: 9. simpozijum Hemija i zaštita životne sredine Kladovo, 4-7. jun 2023. BOOK OF ABSTRACTS : 9th Symposium Chemistry and Environmental Protection Kladovo, 4-7th June 202

Bacterial nanocellulose – new beginning for end-of-life plastics

Introduction: Fossil-based polymers continue to be widely used despite their negative environmental impact. Bioplastics, such as polylactic acid (PLA), offer a promising alternative as they are derived from renewable resources and provide more environmentally friendly end-of-life options. However, marketing PLA assimply biodegradable can be misleading, asthe current PLA degradation strategy contributes to microplastics pollution, thus posing even greater threat. Thisresearch focuses on the upcycling of PLA degradation products into valuable biomaterial - bacterial nanocellulose. Methods: PLA samples were pretreated using ultraviolet and ultrasonic waves, individually and in combination, to enhancessusceptibility to bacterial degradation. Pretreated PLA wassubjected to enzymatic degradation under mild conditions, using various enzyme combinations. The resulting biodegradation products served as a growth medium for nanocellulose producing bacteria Komagataeibacter medellinensis ID13488. Obtained nanocellulose was characterized using SEM, FTIR, AFM, and XRD. Results: The combined PLA pretreatment using ultraviolet and ultrasonic waves, followed by enzymatic degradation with savinase, demonstrated the highest degree of PLA degradation in this study. Furthermore, K. medellinensis ID13488 efficiently utilized the biodegradation products, producing nanocellulose with yields and performance comparable to those obtained through standard cultivation using glucose as a carbon source. Conclusion: This study highlights the potential of combined pretreatment and enzymatic degradation for efficient PLA degradation and sustainable bacterial nanocellulose production. The findings suggest promising avenues for utilizing PLA biodegradation products in the production of other valuable biomaterials. Further research is needed to optimize the pretreatment and degradation processes, facilitating the wider application of biodegradable materials and promoting sustainability

Mechanisms of heavy metal tolerance in free living bacteria and bacterial biofilms

Teški metali, čija se koncentracija u sredini sve više povećava kao rezultat povećane industrijske aktivnosti i tehnološkog razvoja, ubrajaju se u najčešće zagađivače životne sredine. Kada su prisutni u većim koncentracijama toksični su i predstavljaju ozbiljnu pretnju kako za životnu sredinu tako i za zdravlje ljudi, jer se ne mogu razgraditi i jer se nagomilavaju u lancima ishrane. Sa druge strane, ovakve sredine predstavljaju dobar izvor mikroorganizama tolerantnih na teške metale, sa potencijalnom primenom u biološkom uklanjanju (bioremedijaciji) i oslobađanju (bioluženju) teških metala. Cilj ovog rada je bila izolacija, identifikacija, analiza diverziteta i aplikativnog potencijala novih bakterijskih sojeva sa sposobnošću tolerancije visokih koncentracija teških metala iz površinskog i podzemnog sedimenta iz rudnika bakra Bor. Metagenomskom analizom je detektovan veći mikrobiološki diverzitet u uzorku površinskog sedimenta u poređenju sa podzemnim sedimentom. Iz oba uzorka je izolovano 6 bakterija tolerantnih na visoke koncentracije teških metala, primenom direktne kultivacije. Ovi izolati su taksonomski identifikovani kao predstavnici rodova Arthrobacter i Staphylococcus. Pored ovih izolata, u ovu studiju je bilo uključeno još 8 sojeva za koje je tolerancija na metale prethodno opisana u literaturi, tako da je aplikativni potencijal slobodnoživećih bakterija i definisanih bakterijskih zajednica, kao i njihovih biofilmova, ispitan kod ukupno 14 sojeva. Među 14 testiranih sojeva, 6 sojeva je imalo sposobnost rasta u prisustvu nikla, 6 u prisustvu kadmijuma, 4 u prisustvu bakra, 3 u prisustvu hroma i 1 je imao sposobnost rasta u prisustvu žive, dok nijedan od sojeva nije imao sposobnost rasta u prisustvu gvožđa i cinka. Izdvojio se izolat Staphylococcus sp. MSI08, koji je jedini imao sposobnost rasta u prisustvu tri teška metala (nikl, kadmijum, hrom). Analizom genetičkih determinanti mehanizama tolerancije na teške metale, kod 2 soja je detektovano prisustvo gena za determinantu tolerancije na kadmijum, kod 2 soja prisustvo gena za determinantu tolerancije na hrom i kod 2 soja je detektovano prisustvo gena za determinantu tolerancije na bakar. Svi testirani sojevi su imali sposobnost formiranja biofilmova, s tim što su najveći potencijal za formiranje biofilmova pokazali Staphylococcus sp. MUI10, Arthrobacter sp. MSI31, Pseudomonas aeruginosa PAO1 i Cupriavidus metallidurans CH34, dok su Staphylococcus sp. MSI08, Rhodococcus sp. TN113, Pseudomonas putida KT2440 i Cupriavidus necator H16 pokazali nešto slabiji potencijal za formiranje biofilmova...Heavy metals are one of the most common environmental pollutants due to increased industrial activities and technological development. When present in excessive concentrations, heavy metals are highly toxic and they pose a serious threat both to environment and human health, due to their persistence in nature and accumulation in the food chain. On the other hand, polluted sites have proven to be valuable sources of bacteria capable to tolerate increased concentration of heavy metals that could be potentially applied in biological removal (bioremediation) and release (bioleaching) of heavy metals. The aim of this study was to obtain, identify, analyze diversity and application potential of novel bacterial strains with the ability to tolerate high heavy metal concentrations from surface and underground sediments from the copper mine Bor. Metagenomic analysis revealed a higher microbial diversity in surface sediment compared to underground sediment. From both sediments, 6 bacterial strains able to tolerate high heavy metal concentrations were isolated using direct cultivation approach. These isolates were taxonomically identified as members of Arthrobacter and Staphylococcus genus. In addition, this study involved 8 more strains with heavy metal tolerance previously described in the literature. Thus, 14 bacterial strains were included in analysis and evaluation of heavy metal tolerance and application potential of free living bacteria and defined bacterial consortia, as well as their biofilms. Among 14 tested strains, 6 strains had the ability to grow in the presence of nickel, 6 in the presence of cadmium, 4 in the presence of copper, 3 in the presence of chromium and 1 had the ability to grow in the presence of mercury, while none of the strains had the ability to grow in the presence of iron and zinc. Staphylococcus sp. MSI08 singled out as the only strain with the ability to grow in the presence of three heavy metals (nickel, cadmium, chromium). Analysis of genetic determinants conferring heavy metal tolerance revealed presence of cadmium tolerance genes in 2 strains, chromium tolerance genes in 2 strains, and copper tolerance genes were also detected in 2 strains. All strains showed ability to form biofilms, but Staphylococcus sp. MUI10, Arthrobacter sp. MSI31, Pseudomonas aeruginosa PAO1 and Cupriavidus metallidurans CH34 demonstrated the highest potential for the biofilm formation, while Staphylococcus sp. MSI08, Rhodococcus sp. TN113, Pseudomonas putida KT2440 and Cupriavidus necator H16 were less successful in biofilm formation..

Understanding bioplastic materials - Current state and trends

Plastic pollution is now considered one of the largest environmental threats facing humans and animals globally. Development of bioplastic materials may offer part of the solution as bioplastics include both nondegradable and biodegradable materials with both being important for sustainability. Bioplastic materials are currently being designed to encompass minimal carbon footprint, high recycling value and complete biodegradability. This review examines recent developments and trends in the field of bioplastic materials. A range of the most utilized bioplastic materials is presented (poly(lactic acid) (PLA), polyhydroxyalkanoate (PHA), starch, cellulose, bio-based poly(butylene succinate) (bio-PBS) and bio-polyethylene (bio-PE)) including their production, application and degradation options

Degradation behaviour of PCL/PEO/PCL and PCL/PEO block copolymers under controlled hydrolytic, enzymatic and composting conditions

Short-term hydrolytic and enzymatic degradation of poly(epsilon-caprolactone) (PCL), one series of triblock (PCL/PEO/PCL) and the other of diblock (PCL/PEO) copolymers, with a low content of hydrophilic PEO segments is presented. The effect of the introduction of PEO as the central or lateral segment in the PCL chain on copolymer hydrolysis and biodegradation properties was investigated. FUR results revealed higher hydrolytic degradation susceptibility of diblock copolymers due to a higher hydrophilicity compared to PCL and triblock copolymers. Enzymatic degradation was tested using cell-free extracts of Pseudomonas aeruginosa PAO1, for two weeks by following the weight loss, changes in surface roughness, and changes in carbonyl and crystallinity index. The results confirmed that all samples underwent enzymatic degradation through surface erosion which was accompanied with a decrease in molecular weights. Diblock copolymers showed significantly higher weight loss and decrease in molecular weight in comparison to PCL itself and triblock copolymers. AFM analysis confirmed significant surface erosion and increase in RMS values. In addition, biodegradation of polymer films was tested in compost model system at 37 degrees C, where an effective degradation of block copolymers was observed

Analysis of the estimated remaining service life of gas rectification columns

Gas rectification columns are process apparatuses which are very important part of each onshore plant. Sudden failure of these types of columns causes huge daily losses, while fluid leakage can be very dangerous for the people and hazardous for the environment. For that reason, a regular and correct examination of the column is of great importance for the continual process of leading. Together with the detailed examination of the column, a risk-based inspection was applied to maximize savings, both material, time, and costs. The expected remaining service life of rectification columns was also analyzed, while the corrosion rates were calculated according to the various international standards. The minimum required column wall thickness was calculated according to the most commonly used international standard and the obtained difference was analyzed. Detailed analysis of the total risks of the column due to potential failure is presented

Analysis of the estimated remaining service life of gas rectification columns

Gas rectification columns are process apparatuses which are very important part of each onshore plant. Sudden failure of these types of columns causes huge daily losses, while fluid leakage can be very dangerous for the people and hazardous for the environment. For that reason, a regular and correct examination of the column is of great importance for the continual process of leading. Together with the detailed examination of the column, a risk-based inspection was applied to maximize savings, both material, time, and costs. The expected remaining service life of rectification columns was also analyzed, while the corrosion rates were calculated according to the various international standards. The minimum required column wall thickness was calculated according to the most commonly used international standard and the obtained difference was analyzed. Detailed analysis of the total risks of the column due to potential failure is presented

Comparison of the release of selenium nanoparticles from poly (є-caprolactone) microparticles in four different degradation mediums

One of the most prominent properties of poly (є-caprolactone) (PCL) as a biodegradable polymer is slow degradation rate. Due to this advantage the PCL is often used in versatile systems for drug delivery or tissue engineering. When it comes to drug delivery systems, this property of PCL provides the slow release of encapsulated medicaments in order to avoid acute toxicity i.e. to enhance therapeutic efficiency, or protects medicaments from "aggressive" environment and ensures prolonged effect. Selenium nanoparticles (SeNp) recently gained attention as a potential candidate for cancer therapy and prevention with antibacterial properties as well. The major drawback of SeNp is substantial risk of toxicity. Degradation itself is a function of several material properties as well as the nature of surrounding medium. In this work it is examined the release of SeNp from PCL microparticles during the degradation in four different mediums: phosphate buffered saline (PBS), solution of lipase isolated from porcine pancreas in PBS, 0.1 M hydrochloric acid (HCL) and Psseudomonas aeruginosa cell free extract in PBS. The main idea was to compare the release of the selenium nanoparticles in physiological conditions (the first three medium) and in the pathological conditions (the fourth medium), respectively. Firstly, the PCL/SeNp were suspended in adequate medium and placed in water bath at 37 °C. At exact times, samples were collected and examined by different techniques: X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), differential scanning calorimetry (DSC). The release of selenium nanoparticles in physiological conditions occurred in a very slow manner without burst release while in the presence of bacterial extract the release was much more pronounced, even after 24 h

Evaluation of microbial diversity of the microbial mat from the extremely acidic Lake Robule (Bor, Serbia)

Extremely acidic environments are frequently formed in areas impacted by mining activities, and Lake Robule is such an ecosystem. Although an extreme environment, Lake Robule is inhabited by acidophilic microorganisms. We investigated biodiversity of the macroscopic structure known as a microbial mat formed on the lake bottom in shallow waters. Microbial mats are common in acidic environments, but their composition can differ significantly from site to site. Microbial diversity of the mat from Lake Robule was investigated using both cultivation-dependent and metagenomic approaches. The results showed the mat to be mostly inhabited by heterotrophic acidophilic bacteria. When compared to the microbial community of Lake Robule's surface water, the microbial mat proved to be a more complex community. A biogeochemical model of the mat of Lake Robule is proposed on the basis of our results and available published data

Bacterial Nanocellulose as a Scaffold for In Vitro Cell Migration Assay

Bacterial nanocellulose (BNC) stands out among polymers as a promising biomaterial due to its mechanical strength, hydrophilicity, biocompatibility, biodegradability, low toxicity and renewability. The use of scaffolds based on BNC for 3D cell culture has been previously demonstrated. The study exploited excellent properties of the BNC to develop an efficient and low-cost in vitro cell migration assay. The BNC scaffold was introduced into a cell culture 24 h after the SW480 cells were seeded, and cells were allowed to enter the scaffold within the next 24-48 h. The cells were stained with different fluorophores either before or after the introduction of the scaffold in the culture. Untreated cells were observed to enter the BNC scaffold in significant numbers, form clusters and retain a high viability after 48 h. To validate the assay's usability for drug development, the treatments of SW480 cells were performed using aspirin, an agent known to reduce the migratory potential of this cell line in culture. This study demonstrates the application of BNC as a scaffold for cell migration testing as a low-cost alternative to commercial assays based on the Boyden chamber principle. The assay could be further developed for routine use in cancer research and anticancer drug development