Dissertations / Theses on the topic 'Biopolymers – Biodegradation'

The increasing concern for sustainability and progress of medical research has resulted in the emergence of a wide range of biopolymers. The biodegradability of these alternative biopolymers requires investigation prior to their application in environmental and medical systems. This Thesis describes biodegradation of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(HB-co-HV)), poly(3- hydroxyoctanoate) (PHO), poly-DL-lactide (PDLL), poly-DL-lactide-co-glycolide (PDLLG) and ethyl cellulose (EC). Polymers were buried in garden soil for in vivo biodegradation experiments and a mixed population of microbes from the soil were incubated in laboratory in vitro biodegradation experiments. In both systems the short chain length PHA???s degraded rapidly and the medium chain length PHAs and other biomaterials displayed either slow or negligible weight loss. PHB and P(HB-co-HV) copolymers degraded to T50 6.7 to 9.7 times faster in vitro than in vivo. After 380 days burial in soil PHO had lost 60 % of the original 20 mg weight, PDLL 28 % and PDLLG 35 %. Ethyl cellulose and polystyrene did not biodegrade, Polymer-microbe surface interactions were investigated. The faster degrading polymers PHB and P(HB-co-HV) attracted a higher coverage of biofilm than the slower degrading polymers PHO, PDLL and PDLLG for both the in vitro and in vivo experiments. The non-degradable polymers (EC and polystyrene) attracted no biofilm. In vitro and in vivo experiments demonstrated a positive correlation between biofilm coverage and polymer weight loss. Additionally the rougher air sides of solvent cast films attracted more biofilm than the smoother dish sides. Polymer surface changes were quantified with microscopy. Surface roughness of PHB, P(HB-co-8HV) and PHO increased during biodegradation, primarily due to an increase in the waviness component for both in vitro and in vivo degradation. In vitro methods provided a rapid mechanism for protocol development and sufficiently predicted both surface roughness changes and biofilm-biodegradation relationships in vivo. PHB and P(HB-co-8HV) were blended with the biodegradable antifouling agent 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOI or Sea Nine 211). DCOI leached slowly from the films into the soil delaying biodegradation of the films until a lower residual level of DCOI remained. Biofouling was reduced on PHA films containing DCOI.

The development of a "cradle-to-cradle" mindset with both material performance during utilization and end of life disposal is a critical need for both ecological and economic considerations. The main limitation to the use of the biopolymers is their mechanical properties. Reinforcements are therefore a good alternative but disposal concerns then arise. Thus the objective of this dissertation is to investigate a biopolymer nanocomposite where the filler is a synthetically prepared layer double hydroxide (inorganic interface); and a biopolymer paper (organic interface) based coating or laminate. The underlying issues driving performance are the packing density of the biopolymer and the interaction with the reinforcement. Since the polyhydroxyalkanoates or PHAs (the biopolymers used for the manufacture of the nanocomposites and coatings) are semicrystalline materials, the glass transition was investigated using dynamic mechanical analysis (DMA) and dielectric spectroscopy (DES), whereas the melt crystallization, cold crystallization and melting points were investigated using differential scanning calorimetry (DSC). Fourier transform infrared (FTIR) spectroscopy was used to estimate crystallinity in the coated material given the low thermal mass of the PHA in the PHA coating. The significant enhancement of the crystallization rate in the PHA nanocomposite was probed using DSC and polarized optical microscopy (POM) and analyzed using Avrami and Lauritzen-Hoffman models. Both composites showed a significant improvement in the mechanical performance obtained by DMA, tensile and impact testing. The degradation and decomposition of the two composites were investigated in low microbial activity soil for the cellulose paper (to slow down the degradation rate that occurs in compost) and in compost. An in-house system according to the American Society for Testing and Materials ASTM D-98 (2003) was engineered. Soil decomposition showed that PHA coating into and onto the cellulose paper can be considered to be a useful method for the assessment of the degradability of the biopolymer. PHA nanocomposite showed enhanced compostability.

This thesis covers the design of an automated multiunit composting system (AMUCS) that was constructed to meet the experimental apparatus requirements of the ASTM D5338 standard. The design of the AMUCS is discussed in full detail and validated with two experiments. The first experiment was used to validate the operation of the AMUCS with a 15 day experiment. During this experiment visual observations were made to visually observe degradation. Thermal properties and stability tests were performed to quantify the effects of degradation on the polymer samples, and the carbon metabolized from the degradation of samples was measured. The second experiment used the AMUCS to determine the effect of synthetic clay nanofiller on the aerobic biodegradability behavior of poly (3-hydroxybutyrate-co-3-hydroxyvalerate).

Ce travail de thèse s'inscrit dans les thèmes de la photodégradation et de la biodégradation de polymère pouvant être ou non d'origine renouvelable. Il a pour principal objectif d'étudier la durabilité photochimique de différents polymères ou mélanges de polymères utilisés en particulier dans l'agriculture et donc soumis à un vieillissement climatique. La structure chimique des polymères est un des principaux paramètres susceptible d'influencer la photodégradation. Un ensemble de (co)polyesters comportant des unités aliphatiques, cycliques et / ou aromatiques a été sélectionné dans le but d'exprimer une relation structure / photodurabilité. Le photovieillissement des matériaux a été réalisé en conditions naturelles et en conditions accélérées. Des mécanismes de photo-oxydation ont été proposés pour chacun des matériaux à partir de l'évolution des propriétés viscoélastiques traduisant celle de la structure macromoléculaire. Dans ce contexte, l'étude de la durabilité de ces matériaux respectueux de l'environnement doit s'intéresser à des systèmes extrêmement complexes dont chaque constituant est susceptible d'évoluer. Cette caractéristique exige de mettre au point une méthodologie permettant de déterminer la composition d'un biocomposite et d'en suivre les modifications en cours de vieillissement en même temps que l'évolution de la structuration de ces matériaux.

Polihidroxialcanoatos são polímeros biodegradáveis, sintetizados por bactérias a partir de fontes de carbono renováveis. Este trabalho se concentra na produção de P3HB a partir de xilose no contexto de uma usina padrão de álcool e açúcar que produz energia através de cogeração, utiliza resíduos agrícolas de cana-de-açúcar e passaria a produzir etanol de segunda geração a partir do bagaço. A produção de PHAs a partir de xilose, hoje descartada, poderá viabilizar a geração de etanol de segunda geração. Variou-se a produtividade (0,28 e 1,11 g/L.h), o preço (R$ 4,50 R$ 9,00), o custo do fermentador (três cenários entre US$ 475 - 3.013 mil) e a capacidade produtiva da planta (dez cenários de 1.000 a 35.000 mil t/ano). As visões de resultado oferecem a margem de contribuição, lucratividade líquida da operação, bem como o ponto de breakeven. Recomenda-se redirecionar parte dos esforços de pesquisa voltados a um aumento do teor de P3HB na célula para a melhoria da produtividade do processo, que é o fator-chave para que o processo se torne economicamente mais atrativo.
Polyihydroxyalkanoates are biodegradable polymers, synthetized by bacteria from renewable sources of carbon. This thesis focuses on production of P3HB from xylose in the context of a standard sugar and ethanol plant, cogenerates steam and electrical energy utilizing sugarcane bagasse and agricultural residues. PHAs production from xylose, discarded in most mills nowadays, may enable profitability of 2nd generation bioethanol. Productivity varied from 0,28 to 1,11 g/L.h, and PHB price ranged from R$ 4,50 to R$ 9,00 per kilo. Fermentor cost was studied in 3 scenarios from US$ 475 to 3.013 thousand and the production capacity was analyzed in ten different scenarios, from 1,000 to 35,000 thousand tonnes/year. Result reviews offer contribution margin, net operational profit, as well as breakeven point analysis. Recommended is to redirect part of the research efforts from improving P3HB yields to process productivity improvement, which turned out to be the key factor to economic feasibility.

V poslední době se pozornost polečnosti obrátila k mikroplastům. Jsou produkovány různými odvětvími a šíří se napříč prostředím. Po dlouhou dobu byly považovány za inertní, bez dalšího vlivu na rostliny a jiné živé organismy, avšak jak zjistily nedávné studie, mohly by představovat vážnou hrozbu. Několik vědců, včetně nás, se proto začalo soustředit na jejich transport a transformace v životním prostředí. Většina se však zaměřuje pouze na jejich přítomnost v mořských a sladkých vodách, a proto jejich chování ve vzduchu a půdě zůstává nejasné. Kromě toho byla pozornost soustředěna i na bioplasty. Jsou prezentována jako ekologická alternativa, která má vyřešit všechny dosud zmíněné problémy (a další). Avšak často se zapomíná, že jejich hlavní výhoda může být zároveň nevýhodou. Z tohoto důvodu se tato diplomová práce zaměřuje na negativní účinky spojené s přítomností mikroplastů (konkrétně bioplastu poly-(R)-3-hydroxybutyrátu) v půdě jako jejich běžný receptor. Kombinovali jsme respirometrii, elementární analýzu, termogravimetrii a enzymatické testy, abychom zkoumali fyzikálně-chemické změny v půdě vyvolané přítomností bioplastu. Naše výsledky ukázaly negativní vliv na půdní organickou hmotu a zadržování vody v půdě. V tomto smyslu byl zkoumán i tzv. "priming effect", jelikož docházelo k urychlení a také zpomalení rozkladu půdní organické hmoty. Zaznamenali jsme rozdílný vliv vybraných koncentrací biopolymeru na půdu a také vliv půdních vlastností na průběh degradace. V neposlední řadě zvýšení enzymatické aktivity jasně naznačovalo vliv přítomnosti biopolymeru na mikrobiální komunitu. Na základě takových zjištění jsme došli k závěru, že přidání biopolymeru vede k dlouhodobému dopadu na řadu funkcí půdního ekosystému.

A procura por novos materiais que possam substituir parcial ou totalmente os derivados do petróleo, representa um desafio para os pesquisadores na área de ciências dos materiais. Dentro deste contexto, o desenvolvimento de materiais biodegradáveis surge como uma das opções viáveis. A introdução de biopolímeros ou aditivos naturais nas formulações de poliolefinas, utilizadas na indústria de embalagens, tem sido objeto de estudo de vários trabalhos de pesquisa. Acelerar a degradação desses materiais, de modo que a razão custo/benefício de sua produção seja favorável, é um dos objetivos desses estudos. Tem sido relatado que a adição de polidroxibutirato (PHB) à poliolefinas pode contribuir para acelerar a degradação desses materiais. Neste trabalho, misturas de polietileno (PEBD) e PHB foram preparadas em extrusora de rosca dupla, utilizando como carga, a torta de mamona, subproduto do biodiesel. Há um número muito escasso de trabalhos versando sobre a utilização da torta de mamona como aditivo na indústria de plásticos. Há, entretanto, necessidade de se encontrar maiores aplicações para esse resíduo, de forma a tornar a cadeia produtiva do biodiesel mais viável. A avaliação da biodegradação dos produtos obtidos é um dos objetivos específicos deste trabalho. A processabilidade dos materiais e as propriedades mecânicas foram avaliadas por meio dos ensaios convencionais prescritos pelas normas ASTM.. As metodologias de planejamento de experimentos: planejamento fatorial e modelagem de misturas foram utilizadas, respectivamente, para determinação das melhores condições de processamento e para avaliar o efeito da proporção dos componentes das misturas nas propriedades obtidas. O software Minitab foi usado com esta finalidade. A morfologia das misturas foi avaliada através de microscopia eletrônica de varredura (MEV). A biodegradação foi avaliada em solo simulado por diferentes períodos de tempo através de determinações de perda de massa das amostras. Os resultados obtidos demonstraram que a adição do PHB e da mamona ao PEBD levam a obtenção de propriedades superiores de flexão e ao aumento de Módulo de Young. A resistência à tração e as propriedades de impacto do PEBD se deterioraram com a adição do PHB, assim como com a adição da carga. As misturas ternárias com maior teor de PHB apresentaram biodegradação mais acentuada. A mistura com a composição polietileno, poli(3-hidroxibutirato) e torta de mamona ( 70%/20%/10%) sofreu degradação mais acelerada que as misturas binárias. Este fato sugere que a torta de mamona catalisa a degradação dos materiais, fato este que pode ser atribuído à morfologia da mistura ternária.

Le risque d'épuisement de ressources naturelles fossiles à partir desquelles nombres d'oléfines sont fabriqués, a permis le développement de nouveaux matériaux polymères, 100% renouvelables dénommés biopolymères. L'acide poly lactique est sans doute le plus prometteur d'entre eux. D'origine naturelle, ce polyester est synthétisé à partir d'aliments riches en amidon tels que le maïs, la betterave ou la pomme de terre. Son caractère biodégradable lui offre un large éventail d'applications dans les domaines aussi variés et divers que la médecine, le bâtiment, l'industrie automobile, le biomédicale ou encore le textile habillement. Ce travail consiste à étudier la structure et la texture de l'isomère mixte (PDLA) et de déterminer l'incidence de sa morphologie sur les propriétés mécaniques et tinctoriales requises pour des applications textiles. Nous avons par des méthodes spectrales, caractérisé le polymère afin d'en déterminer entre autre, la composition massique, et la stéréorégularité, paramètres très importants ayant une forte influence sur les propriétés mécaniques du polymère, notamment la stabilité thermique ou la résistance à l'hydrolyse. Nos expériences menées sur la stabilité thermique du polymère révèlent que le polymère est susceptible de s'hydrolyser sous l'action combinée de l'eau, de la température et du pH, entraînant ainsi une diminution de la masse moléculaire, donc, une perte de propriétés mécaniques de la fibre.Le PLA est également un polymère qui supporte mal la teinture, et seuls les colorants dispersés sont susceptibles de teinte cette fibre sous certaines conditions. L'étude de la cinétique de fixation de trois colorants dispersés sur la fibre de PLA à permis d'établir une relation entre la structure du colorant et ses propriétés tinctoriales.

This master’s thesis deals with the study of composting of polyhydroxybutyrate (PHB) and polylactic acid (PLA). The experimental part focuses on the composting test based on the IS/ISO 20200 standard, in which biopolymers were degraded within 8 weeks. The advantage of the composting test was the unique use of bags for polymer granules, which simplified the handling of samples. The placement of the polymers ensured an even load of compost, which simulated the landfill environment, which also made this experiment exceptional. The use of different methods of analysis ensured the investigation of the influence of compost on the degradation of polymers, but also the influence of polymers on the compost microbiome. In the compost environment all of the studied polymers degraded. After 8 weeks the weight loss of approximately 40 % was detected in PHB. Amorphous PLA degraded completely in the 5th week of experiment, while semicrystalline PLA lost approximately 70 % of its weight in 8 weeks. Using SEM images and SEC analysis, we conclude that PHB degradation was predominantly biological. Degradation of PLA samples was found to be predominantly abiotic. Analysis of compost samples revealed that the enzymatic activity of esterases increased in composts with polymers compared to compost without polymers. The effect of polymers on the microbiome in compost was analyzed using Biolog EcoPlates™. Compost with PHB showed a high ability to adapt to various substrates and microbiome expanded during composting. In the case of a sample with semicrystalline PLA, it was found that in the last week of composting, the ability of microorganisms to adapt and use substrates decreased, which indicates a possible negative effect of this polymer on compost development.

The goal of drinking water treatment is to produce and deliver safe water to the consumers. To achieve these objectives water treatment plants are designed based on the concept of the multibarrier approach which combines several drinking water treatment processes in order to increase the reliability of the system. The presence of pharmaceutically active compounds (PhACs), personal care products (PCPs) and endocrine disrupting compounds (EDCs) in drinking water sources is becoming a concern, because of chronic and indirect human exposure to contaminant mixtures at sub-therapeutic levels via drinking water consumption. Membrane filtration can be an efficient treatment process to remove microorganisms and/or trace organic contaminants from drinking water sources. However, membranes are confronted by a major limitation: membrane fouling. Fouled membranes suffer from a loss in performance either leading to a reduction in flux or a higher pressure requirement. Generally, membrane fouling increases the need for membrane maintenance measures such as backwashing and chemical cleaning which has a negative impact on the operating costs and membrane life time. Severe membrane fouling may even impact permeate quality and/or compromise membrane integrity. The aim of this study was to establish if biofiltration pretreatment without prior coagulation would be able to control membrane fouling in natural waters. The second objective investigated the removal of trace organic contaminants by individual treatment processes (i.e. biofiltration and membrane filtration). Parallel to this work, the presence and concentration of selected trace organic contaminants in Grand River (Ontario, Canada) were determined. The trace organic contaminants investigated included atrazine, carbamazepine, DEET, ibuprofen, naproxen, and nonylphenol. Direct biofiltration pretreatment (no coagulation) significantly reduced both reversible and irreversible fouling of ultrafiltration membranes. Results showed that the different degree of reduction of hydraulically reversible fouling was primarily attributed to the absolute concentration of a specific fraction of the dissolved organic matter (i.e. biopolymers) in the biofilter effluent (i.e. membrane feed). The study also suggests that the composition of biopolymers rather than their absolute concentration is important for the control of irreversible fouling. High pressure membranes such as nanofiltration membranes are also subjected to fouling. Results showed that biofiltration pretreatment was able to achieve fouling control but membrane characteristics (i.e. molecular weight cut off) influence the efficiency of the pretreatment. This study also showed that not only biopolymers but also humic substances and low molecular weight acids are being rejected by nanofiltration membranes. Selected trace organic contaminants were detected in Grand River water in the low ng/L range with detection frequencies between 48 to 100%. Seasonal occurrence patterns could be explained by compound use and possible degradation mechanisms. These results confirm the impact of human activities on the Grand River. This study showed that under the right conditions rapid biofiltration is capable of completely removing biodegradable emerging contaminants at ng/L concentrations. DEET, ibuprofen, and naproxen were biodegradable and therefore amenable to removal while carbamazepine and atrazine were recalcitrant. Factors such as empty bed contact time, influent concentration, and temperature influenced the biodegradation kinetics. Finally, both membrane and contaminant properties influenced the degree of rejection achieved by nanofiltration membranes. Results showed that steric hindrance and electrostatic repulsion were the major rejection mechanisms. Several benefits are associated with the use of direct biofiltration for drinking water treatment. These benefits include: the removal of easily biodegradable organic matter leading to biologically stable effluents; the removal of biodegradable trace organic contaminants contributing to the multibarrier approach; the absence of chemicals coagulation which is of advantage for operations in isolated areas; the simple operation and maintenance which is an advantage for locations with limited trained operators; and finally if used prior to membrane filtration biofiltration pretreatment can control membrane fouling.

博士
國立中興大學
環境工程學系所
96
Chlorophenolic compounds are common environmental contaminants and they are hazardous to human being. Especially pentachlorophenol (PCP) is toxic to all forms of life since it is an oxidative phosphorylation inhibitor. Thus, removing them from environment and decreasing their toxicity is an important issue. Biological treatment is harmless environmental friendly and relative economical treated procedure. Therefore, one part of this research focused on phenol and chlorophenols (CPs) biodegradation. In this field, pure phenol and CPs degrading pure strains were enriched, isolated and characterized. Moreover, PCP-degrading strain Sphingobium chlorophenolicum PCP-1 isolated previously was applied for PCP-contaminated groundwater bioremediation, and its genes involving in PCP degradation were also identified, sequencing and expressed. From phenol and CPs acclimated mixed cultures, we isolated and identified two phenol-degrading strains (Pseudomonas resinovorans strain P-1 and Brevibacillus sp. strain P-6), one 4-CP-degrading strain (Rhizobium sp. 4-CP-20) and one 2,4-dichlorophenol (2,4-DCP) strain (Burkholderia cepacia strain 1-3b). After investigation, the optimum growth temperatures for strain P-1 and P-6 were 31°C and 39°C respectively. Strain P-1 could degrade 600 mg/l phenol completely within 57.5 hr, and the maximum degraded phenol concentration of stain P-6 was 200 mg/l within 93.1 hr. Strain P-1 showed higher applied potential than strain P-6. The optimum growth temperature and 4-CP degrading pH for strain 4-CP-20 were 36°C and 7.59, respectively. Strain 4-CP-20 could degrade 100 mg/l 4-CP completely within 3.95 days, but the bacterial growth and the 4-CP degrading activity were both inhibited while the initial 4-CP concentration was higher than 240 mg/l. The maximum 2,4-DCP degrading concentration of strain 1-3b was 75 mg/l. Strain 1-3b not only utilized 2,4-DCP but also phenol, 2-CP and 4-CP as sole carbon source. After inoculating immobilized Sphingobium cells to bioremediate PCP-contaminated groundwater with a biological treatment system, the results indicated the immobilized cells could be inoculated into PCP-contaminated groundwater without adding other supplementary nitrogen, phosphate and carbon sources. The optimum HRT in the bioreactor system was 12.6 hr. PCP removal in the bioreactor remained stable and PCP removal efficiency was higher than 92% at this phase, and PCP concentration in the biotreatment system effluent remained undetectable. It is possible to bioremediate PCP-contaminated groundwater using immobilized Sphingobium cells in a bioreactor system. The proposed biological treatment system could be maintained for at least for two months. Besides, PCP metabolic pathway of strain Sphingomonas chlorophenolica PCP-1 was the same with previous study, and its PCP-degrading genes pcpA, pcpB, pcpC, pcpD and pcpE were sequenced. Gene pcpB was successfully expressed with pET-system, but the expressed protein was aggregated into inclusion body form. Another part of this study was concerned with recalcitrant biopolymer biodegradation. Polythioesters (PTEs) are the newest eighth class of biopolymers, and the first PTEs member was identified in 2001. Among PTEs, homopolymer poly(3-mercaptobutyrate) (PMP) synthesized using non-natural pathway displays good potential for application. However, before its extensive utilization, the PMP biodegradability has to be addressed more throughoutly. In this field, PHA depolymerase genes (phaZ1, phaZ5 and phaZ7) from strain Paucimonas lemoignei were identified, sequenced, expressed and mutated. Our result demonstrated that gene phaZ1 and phaZ5 of strain P. lemoignei could be expressed by strain E. coli and pET-23a system and the expressed proteins contained activities of degrading dPHB granules. After mutation with XL1-red competent cells system and UV light, no mutant containing PMP degrading ability was successfully screened. The third gene phaZ7 also could be expressed, but its nPHB degrading ability was not detectable. According to all results mentioned above, we can summarize that functional strains could be applied successfully for bioremediation after appropriate enrichment and detailed characterization. Moreover, basing on the role of molecular biotechnology on environmental engineering becomes gradually important. To approach recalcitrant compounds biodegradation, sometimes genomic engineering methods could be powerful tools and the background of functional genes in functional strain also must be investigated carefully. We tried to change the substrate specificity of gene phaZ using molecular biotechnological methods. However, the results were not so successful.