Disintegrability under composting conditions of plasticized PLA–PHB blends

The disintegration under composting conditions of films based on poly(lactic acid)–poly(hydroxybutyrate) (PLA–PHB) blends and intended for food packaging was studied. Two different plasticizers, poly(ethylene glycol) (PEG) and acetyl-tri-n-butyl citrate (ATBC), were used to limit the inherent brittleness of both biopolymers. Neat PLA, plasticized PLA and PLA–PHB films were processed by melt-blending and compression molding and they were further treated under composting conditions in a laboratory-scale test at 58 ± 2 °C. Disintegration levels were evaluated by monitoring their weight loss at different times: 0, 7, 14, 21 and 28 days. Morphological changes in all formulations were followed by optical and scanning electron microscopy (SEM). The influence of plasticizers on the disintegration of PLA and PLA–PHB blends was studied by evaluating their thermal and nanomechanical properties by thermogravimetric analysis (TGA) and the nanoindentation technique, respectively. Meanwhile, structural changes were followed by Fourier transformed infrared spectroscopy (FTIR). The ability of PHB to act as nucleating agent in PLA–PHB blends slowed down the PLA disintegration, while plasticizers speeded it up. The relationship between the mesolactide to lactide forms of PLA was calculated with a Pyrolysis–Gas Chromatography–Mass Spectrometry device (Py–GC/MS), revealing that the mesolactide form increased during composting.

Processing and characterization of plasticized PLA/PHB blends for biodegradable multiphase systems

Blends of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) plasticized with a lactic acid oligomer (OLA) added at three different concentrations (15, 20 and 30 wt% by weight), were prepared by an optimized extrusion process to improve the processability and mechanical properties of these biopolymers for flexible film manufacturing. Morphological, chemical, thermal, mechanical, barrier and migration properties were investigated and formulations with desired performance in eco-friendly films were selected. The efficiency of OLA as plasticizer for PLA_PHB blends was demonstrated by the significant decrease of their glass transition temperatures and a considerable improvement of their ductile properties. The measured improvements in the barrier properties are related to the higher crystallinity of the plasticized PLA_PHB blends, while the overall migration test underlined that all the proposed formulations maintained migration levels below admitted levels. The PLA_PHB blend with 30 wt% OLA was selected as the optimum formulation for food packaging, since it offered the best compromise between ductility and oxygen and water vapor barrier properties with practically no migration.

Inhibition of cell-wall autolysis and pectin degradation by cations

Modification of cell wall components such as cellulose, hemicellulose and pectin plays an important role in cell expansion. Cell expansion is known to be diminished by cations but it is unknown if this results from cations reacting with pectin or other cell wall components. Autolysis of cell wall material purified from bean root (Phaseolus vulgaris L.) occurred optimally at pH 5.0 and released mainly neutral sugars but very little uronic acid. Autolytic release of neutral sugars and uronic acid was decreased when cell wall material was loaded with Ca, Cu, Sr, Zn, Al or La cations. Results were also extended to a metal-pectate model system, which behaved similarly to cell walls and these cations also inhibited the enzymatic degradation by added polygalacturonase (EC 3.2.1.15). The extent of sugar release from cation-loaded cell wall material and pectate gels was related to the degree of cation saturation of the substrate, but not to the type of cation. The binding strength of the cations was assessed by their influence on the buffer capacity of the cell wall and pectate. The strongly bound cations (Cu, Al or La) resulted in higher cation saturation of the substrate and decreased enzymatic degradability than the weakly held cations (Ca, Sr and Zn). The results indicate that the junction zones between pectin molecules can peel open with weakly held cations, allowing polygalacturonase to cleave the hairy region of pectin, while strongly bound cations or high concentrations of cations force the junction zone closed, minimising enzymatic attack on the pectin backbone. (C) 2004 Elsevier SAS. All rights reserved.

Comparison of the effect of pre-treatment and catalysts on liquid quality from fast pyrolysis of biomass

The overall objective of this work was to compare the effect of pre-treatment and catalysts on the quality of liquid products from fast pyrolysis of biomass. This study investigated the upgrading of bio-oil in terms of its quality as a bio-fuel and/or source of chemicals. Bio-oil used directly as a biofuel for heat or power needs to be improved particularly in terms of temperature sensitivity, oxygen content, chemical instability, solid content, and heating values. Chemicals produced from bio-oil need to be able to meet product specifications for market acceptability. There were two main objectives in this research. The first was to examine the influence of pre-treatment of biomass on the fast pyrolysis process and liquid quality. The relationship between the method of pre-treatment of biomass feedstock to fast pyrolysis oil quality was studied. The thermal decomposition behaviour of untreated and pretreated feedstocks was studied by using a TGA (thermogravimetric analysis) and a Py-GC/MS (pyroprobe-gas chromatography/mass spectrometry). Laboratory scale reactors (100g/h, 300g/h, 1kg/h) were used to process untreated and pretreated feedstocks by fast pyrolysis. The second objective was to study the influence of numerous catalysts on fast pyrolysis liquids from wheat straw. The first step applied analytical pyrolysis (Py-GC/MS) to determine which catalysts had an effect on fast pyrolysis liquid, in order to select catalysts for further laboratory fast pyrolysis. The effect of activation, temperature, and biomass pre-treatment on catalysts were also investigated. Laboratory experiments were also conducted using the existing 300g/h fluidised bed reactor system with a secondary catalytic fixed bed reactor. The screening of catalysts showed that CoMo was a highly active catalyst, which particularly reduced the higher molecular weight products of fast pyrolysis. From these screening tests, CoMo catalyst was selected for larger scale laboratory experiments. With reference to the effect of pre-treatment work on fast pyrolysis process, a significant effect occurred on the thermal decomposition of biomass, as well as the pyrolysis products composition, and the proportion of key components in bio-oil. Torrefaction proved to have a mild influence on pyrolysis products, when compared to aquathermolysis and steam pre-treatment.

Improvement of bio-oil stability in wood pyrolysis process

Pyrolysis is one of several thermochemical technologies that convert solid biomass into more useful and valuable bio-fuels. Pyrolysis is thermal degradation in the complete or partial absence of oxygen. Under carefully controlled conditions, solid biomass can be converted to a liquid known as bie-oil in 75% yield on dry feed. Bio-oil can be used as a fuel but has the drawback of having a high level of oxygen due to the presence of a complex mixture of molecular fragments of cellulose, hemicellulose and lignin polymers. Also, bio-oil has a number of problems in use including high initial viscosity, instability resulting in increased viscosity or phase separation and high solids content. Much effort has been spent on upgrading bio-oil into a more usable liquid fuel, either by modifying the liquid or by major chemical and catalytic conversion to hydrocarbons. The overall primary objective was to improve oil stability by exploring different ways. The first was to detennine the effect of feed moisture content on bio-oil stability. The second method was to try to improve bio-oil stability by partially oxygenated pyrolysis. The third one was to improve stability by co-pyrolysis with methanol. The project was carried out on an existing laboratory pyrolysis reactor system, which works well with this project without redesign or modification too much. During the finishing stages of this project, it was found that the temperature of the condenser in the product collection system had a marked impact on pyrolysis liquid stability. This was discussed in this work and further recommendation given. The quantity of water coming from the feedstock and the pyrolysis reaction is important to liquid stability. In the present work the feedstock moisture content was varied and pyrolysis experiments were carried out over a range of temperatures. The quality of the bio-oil produced was measured as water content, initial viscosity and stability. The result showed that moderate (7.3-12.8 % moisture) feedstock moisture led to more stable bio-oil. One of drawbacks of bio-oil was its instability due to containing unstable oxygenated chemicals. Catalytic hydrotreatment of the oil and zeolite cracking of pyrolysis vapour were discllssed by many researchers, the processes were intended to eliminate oxygen in the bio-oil. In this work an alternative way oxygenated pyrolysis was introduced in order to reduce oil instability, which was intended to oxidise unstable oxygenated chemicals in the bio-oil. The results showed that liquid stability was improved by oxygen addition during the pyrolysis of beech wood at an optimum air factor of about 0.09-0.15. Methanol as a postproduction additive to bio-oil has been studied by many researchers and the most effective result came from adding methanol to oil just after production. Co-pyrolysis of spruce wood with methanol was undertaken in the present work and it was found that methanol improved liquid stability as a co-pyrolysis solvent but was no more effective than when used as a postproduction additive.

Microencapsulation studies with P(HB-HV) polymers

Microencapsulation processes, based upon the concept of solvent evaporation, have been employed within these studies to prepare microparticles from poly--hydroxybutyrate homopolymers and copolymers thereof with 3-hydroxyvalerate [P(HB-HV) polymers]. Variations in the preparative technique have facilitated the manufacture of two structurally distinct forms of microparticle. Thus, monolithic microspheres and reservoir-type microcapsules have been respectively fabricated by single and double emulsion-solvent evaporation processes. The objective of the studies reported in chapter three is to asses how a range of preparative variables affect the yield, shape and surface morphology of P(HB-HV) microcapsules. The following chapter then describes how microcapsule morphology in general, and microcapsule porosity in particular, can be regulated by blending the fabricating P(HB-HV) polymer with poly--caprolactone [PCL]. One revelation of these studies is the ability to generate uniformly microporous microcapsules from blends of various high molecular weight P(HB-HV) polymers with a low molecular weight form of PCL. These microcapsules are of particular interest because they may have the potential to facilitate the release of an encapsulated macromolecule via an aqueous diffusion mechanism which is not reliant on polymer degradation. In order to investigate this possibility, one such formulation is used in chapter five to encapsulate a wide range of different macromolecules, whose in vitro release behaviour is subsequently evaluated. The studies reported in chapter six centre on the preparation and characterization of hydrocortisone-loaded microspheres, prepared from a range of P(HB-HV) polymers, using a single emulsion-solvent evaporation process. In this chapter, the influence of the organic phase viscosity on the efficiency of drug encapsulation is the focus of initial investigations. Thereafter, it is shown how the strategies previously adopted for the regulation of microcapsule morphology can also be applied to single emulsion systems, with profound implications for the rate of drug release.

Fast pyrolysis and nitrogenolysis of biomass and biogenic residues:production of a sustainable slow release fertiliser

The production of agricultural and horticultural products requires the use of nitrogenous fertiliser that can cause pollution of surface and ground water and has a large carbon footprint as it is mainly produced from fossil fuels. The overall objective of this research project was to investigate fast pyrolysis and in-situ nitrogenolysis of biomass and biogenic residues as an alternative route to produce a sustainable solid slow release fertiliser mitigating the above stated problems. A variety of biomasses and biogenic residues were characterized by proximate analysis, ultimate analysis, thermogravimetric analysis (TGA) and Pyrolysis – Gas chromatography – Mass Spectroscopy (Py–GC–MS) for their potential use as feedstocks using beech wood as a reference material. Beech wood was virtually nitrogen free and therefore suitable as a reference material as added nitrogen can be identified as such while Dried Distillers Grains with Solubles (DDGS) and rape meal had a nitrogen content between 5.5wt.% and 6.1wt.% qualifying them as high nitrogen feedstocks. Fast pyrolysis and in-situ nitrogenolysis experiments were carried out in a continuously fed 1kg/h bubbling fluidized bed reactor at around 500°C quenching the pyrolysis vapours with isoparaffin. In-situ nitrogenolysis experiments were performed by adding ammonia gas to the fast pyrolysis reactor at nominal nitrogen addition rates between 5wt.%C and 20wt.%C based on the dry feedstock’s carbon content basis. Mass balances were established for the processing experiments. The fast pyrolysis and in-situ nitrogenolysis products were characterized by proximate analysis, ultimate analysis and GC– MS. High liquid yields and good mass balance closures of over 92% were obtained. The most suitable nitrogen addition rate for the in-situ nitrogenolysis experiments was determined to be 12wt.%C on dry feedstock carbon content basis. However, only a few nitrogen compounds that were formed during in-situ nitrogenolysis could be identified by GC–MS. A batch reactor process was developed to thermally solidify the fast pyrolysis and in-situ nitrogenolysis liquids of beech wood and Barley DDGS producing a brittle solid product. This was obtained at 150°C with an addition of 2.5wt% char (as catalyst) after a processing time of 1h. The batch reactor was also used for modifying and solidifying fast pyrolysis liquids derived from beech wood by adding urea or ammonium phosphate as post processing nitrogenolysis. The results showed that this type of combined approach was not suitable to produce a slow release fertiliser, because the solid product contained up to 65wt.% of highly water soluble nitrogen compounds that would be released instantly by rain. To complement the processing experiments a comparative study via Py–GC–MS with inert and reactive gas was performed with cellulose, hemicellulose, lignin and beech wood. This revealed that the presence of ammonia gas during analytical pyrolysis did not appear to have any direct impact on the decomposition products of the tested materials. The chromatograms obtained showed almost no differences between inert and ammonia gas experiments indicating that the reaction between ammonia and pyrolysis vapours does not occur instantly. A comparative study via Fourier Transformed Infrared Spectroscopy of solidified fast pyrolysis and in-situ nitrogenolysis products showed that there were some alterations in the spectra obtained. A shift in frequencies indicating C=O stretches typically related to the presence of carboxylic acids to C=O stretches related to amides was observed and no double or triple bonded nitrogen was detected. This indicates that organic acids reacted with ammonia and that no potentially harmful or non-biodegradable triple bonded nitrogen compounds were formed. The impact of solid slow release fertiliser (SRF) derived from pyrolysis and in-situ nitrogenolysis products from beech wood and Barley DDGS on microbial life in soils and plant growth was tested in cooperation with Rothamsted Research. The microbial incubation tests indicated that microbes can thrive on the SRFs produced, although some microbial species seem to have a reduced activity at very high concentrations of beech wood and Barley DDGS derived SRF. The plant tests (pot trials) showed that the application of SRF derived from beech wood and barley DDGS had no negative impact on germination or plant growth of rye grass. The fertilizing effect was proven by the dry matter yields in three harvests after 47 days, 89 days and 131 days. The findings of this research indicate that in general a slow release fertiliser can be produced from biomass and biogenic residues by in-situ nitrogenolysis. Nevertheless the findings also show that additional research is necessary to identify which compounds are formed during this process.

Uncatalysed and potassium-catalysed pyrolysis of the cell-wall constituents of biomass and their model compounds

Cell-wall components (cellulose, hemicellulose (oat spelt xylan), lignin (Organosolv)), and model compounds (levoglucosan (an intermediate product of cellulose decomposition) and chlorogenic acid (structurally similar to lignin polymer units)) have been investigated to probe in detail the influence of potassium on their pyrolysis behaviours as well as their uncatalysed decomposition reaction. Cellulose and lignin were pretreated to remove salts and metals by hydrochloric acid, and this dematerialized sample was impregnated with 1% of potassium as potassium acetate. Levoglucosan, xylan and chlorogenic acid were mixed with CHCOOK to introduce 1% K. Characterisation was performed using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In addition to the TGA pyrolysis, pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) analysis was introduced to examine reaction products. Potassium-catalysed pyrolysis has a huge influence on the char formation stage and increases the char yields considerably (from 7.7% for raw cellulose to 27.7% for potassium impregnated cellulose; from 5.7% for raw levoglucosan to 20.8% for levoglucosan with CHCOOK added). Major changes in the pyrolytic decomposition pathways were observed for cellulose, levoglucosan and chlorogenic acid. The results for cellulose and levoglucosan are consistent with a base catalysed route in the presence of the potassium salt which promotes complete decomposition of glucosidic units by a heterolytic mechanism and favours its direct depolymerization and fragmentation to low molecular weight components (e.g. acetic acid, formic acid, glyoxal, hydroxyacetaldehyde and acetol). Base catalysed polymerization reactions increase the char yield. Potassium-catalysed lignin pyrolysis is very significant: the temperature of maximum conversion in pyrolysis shifts to lower temperature by 70 K and catalysed polymerization reactions increase the char yield from 37% to 51%. A similar trend is observed for the model compound, chlorogenic acid. The addition of potassium does not produce a dramatic change in the tar product distribution, although its addition to chlorogenic acid promoted the generation of cyclohexane and phenol derivatives. Postulated thermal decomposition schemes for chlorogenic acid are presented. © 2008 Elsevier B.V. All rights reserved.

Phosphorus catalysis in the pyrolysis behaviour of biomass

Phosphorus is a key plant nutrient and as such, is incorporated into growing biomass in small amounts. This paper examines the influence of phosphorus, present in either acid (HPO) or salt ((NH)PO) form, on the pyrolysis behaviour of both Miscanthus × giganteus, and its cell wall components, cellulose, hemicellulose (xylan) and lignin (Organosolv). Pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) is used to examine the pyrolysis products during thermal degradation, and thermogravimetric analysis (TGA) is used to examine the distribution of char and volatiles. Phosphorus salts are seen to catalyse the pyrolysis and modify the yields of products, resulting in a large increase in char yield for all samples, but particularly for cellulose and Miscanthus. The thermal degradation processes of cellulose, xylan and Miscanthus samples occur in one step and the main pyrolysis step is shifted to lower temperature in the presence of phosphorus. A small impact of phosphorus was observed in the case of lignin char yields and the types of pyrolysis decomposition products produced. Levoglucosan is a major component produced in fast pyrolysis of cellulose. Furfural and levoglucosenone become more dominant products upon P-impregnation pointing to new rearrangement and dehydration routes. The P-catalysed xylan decomposition route leads to a much simpler mixture of products, which are dominated by furfural, 3-methyl-2-cyclopenten-1-one and one other unconfirmed product, possibly 3,4-dihydro-2-methoxy-2H-pyran or 4-hydroxy-5,6-dihydro-(2H)-pyran-2-one. Phosphorus-catalysed lignin decomposition also leads to a modified mixture of tar components and desaspidinol as well as other higher molecular weight component become more dominant relative to the methoxyphenyl phenols, dimethoxy phenols and triethoxy benzene. Comparison of the results for Miscanthus lead to the conclusion that the understanding of the fast pyrolysis of biomass can, for the most part, be gained through the study of the individual cell wall components, provided consideration is given to the presence of catalytic components such as phosphorus.

Pryolytic and kinetic study of Chlorella Vulgaris under isothermal and non-isothermal conditions

Algae are a new potential biomass for energy production but there is limited information on their pyrolysis and kinetics. The main aim of this thesis is to investigate the pyrolytic behaviour and kinetics of Chlorella vulgaris, a green microalga. Under pyrolysis conditions, these microalgae show their comparable capabilities to terrestrial biomass for energy and chemicals production. Also, the evidence from a preliminary pyrolysis by the intermediate pilot-scale reactor supports the applicability of these microalgae in the existing pyrolysis reactor. Thermal decomposition of Chlorella vulgaris occurs in a wide range of temperature (200-550°C) with multi-step reactions. To evaluate the kinetic parameters of their pyrolysis process, two approaches which are isothermal and non-isothermal experiments are applied in this work. New developed Pyrolysis-Mass Spectrometry (Py-MS) technique has the potential for isothermal measurements with a short run time and small sample size requirement. The equipment and procedure are assessed by the kinetic evaluation of thermal decomposition of polyethylene and lignocellulosic derived materials (cellulose, hemicellulose, and lignin). In the case of non-isothermal experiment, Thermogravimetry- Mass Spectrometry (TG-MS) technique is used in this work. Evolved gas analysis provides the information on the evolution of volatiles and these data lead to a multi-component model. Triplet kinetic values (apparent activation energy, pre-exponential factor, and apparent reaction order) from isothermal experiment are 57 (kJ/mol), 5.32 (logA, min-1), 1.21-1.45; 9 (kJ/mol), 1.75 (logA, min-1), 1.45 and 40 (kJ/mol), 3.88 (logA, min-1), 1.45- 1.15 for low, middle and high temperature region, respectively. The kinetic parameters from non-isothermal experiment are varied depending on the different fractions in algal biomass when the range of apparent activation energies are 73-207 (kJ/mol); pre-exponential factor are 5-16 (logA, min-1); and apparent reaction orders are 1.32–2.00. The kinetic procedures reported in this thesis are able to be applied to other kinds of biomass and algae for future works.

Experiments on the generation of activated carbon from biomass

Activated carbon is generated from various waste biomass sources like rice straw, wheat straw, wheat straw pellets, olive stones, pistachios shells, walnut shells, beech wood and hardcoal. After drying the biomass is pyrolysed in the temperature range of 500-600 °C at low heating rates of 10 K/min. The activation of the chars is performed as steam activation at temperatures between 800 °C and 900 °C. Both the pyrolysis and activation experiments were run in lab-scale facilities. It is shown that nut shells provide high active surfaces of 1000-1300 m/g whereas the active surface of straw matters does hardly exceed 800 m/g which might be a result of the high ash content of the straws and the slightly higher carbon content of the nut shells. The active surface is detected by BET method. Besides the testing of a many types of biomass for the suitability as base material in the activated carbon production process, the experiments allow for the determination of production parameters like heating rate and pyrolysis temperature, activation time and temperature as well as steam flux which are necessary for the scale up of the process chain. © 2006 Elsevier B.V. All rights reserved.

Potassium catalysis in the pyrolysis behaviour of short rotation willow coppice

Short rotation willow coppice (SRC) and a synthetic biomass, a mixture of the basic biomass components (cellulose, hemicellulose and lignin), have been investigated for the influence of potassium on their pyrolysis behaviours. The willow sample was pre-treated to remove salts and metals by hydrochloric acid, and this demineralised sample was impregnated with potassium. The same type of pre-treatment was applied to components of the synthetic biomass. Characterisation was performed using thermogravimetric analysis with measurement of products by means of Fourier transform infrared spectroscopy (TGA-FTIR) and pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). A comparison of product distributions and kinetics are reported. While the general features of decomposition of SRC are described well by an additive behaviour of the individual components, there are some differences in the magnitude of the influence of potassium, and on the products produced. For both SRC and the synthetic biomass, TGA traces indicate catalytic promotion of both of the two-stages of biomass decomposition, and potassium can lower the average apparent first-order activation energy for pyrolysis by up to 50 kJ/mol. For both SRC and synthetic biomass the yields and distribution of pyrolysis products have been influenced by the presence of the catalyst. Potassium catalysed pyrolysis increases the char yields markedly and this is more pronounced for synthetic biomass than SRC. Gas evolution profiles during pyrolysis show the same general features for both SRC and synthetic biomass. Relative methane yields increase during the char formation stage of pyrolysis of the potassium doped samples. The evolution profiles of acetic acid and formaldehyde change, and these products are seen in lower relative amounts for both the demineralised samples. A greater variation in pyrolysis products is observed from the treated SRC samples compared to the different synthetic biomass samples. Furthermore, substituted phenols from lignin pyrolysis are more dominant in the pyrolysis profiles of the synthetic biomass than of the SRC, implying that the extracted lignins used in the synthetic biomass yield a greater fraction of monomeric type species than the lignocellulosic cell wall material of SRC. For both types of samples, PY-GS-MS analyses show that potassium has a significant influence on cellulose decomposition markers, not just on the formation of levoglucosan, but also other species from the non-catalysed mechanism, such as 3,4-dihydroxy-3-cyclobutene-1,2-dione. © 2007 Elsevier Ltd. All rights reserved.

Element characteristic tolerance for semi-batch fixed bed biomass pyrolysis

Biomass pyrolysis to bio-oil is one of the promising sustainable fuels. In this work, relation between biomass feedstock element characteristic and crude bio-oil production yield and lower heating value was explored. The element characteristics considered in this study include moisture, ash, fix carbon, volatile matter, C, H, N, O, S, cellulose, hemicellulose, and lignin content. A semi-batch fixed bed reactor was used for biomass pyrolysis with heating rate of 30 °C/min from room temperature to 600 °C and the reactor was held at 600 °C for 1 h before cooling down. Constant nitrogen flow (1bar) was provided for anaerobic condition. Sago and Napier glass were used in the study to create different element characteristic of feedstock by altering mixing ratio. Comparison between each element characteristic to crude bio-oil yield and low heating value was conducted. The result suggested potential key element characteristic for pyrolysis and provide a platform to access the feedstock element acceptance range.

Desenvolvimento e crescimento da espécie de cogumelo Pleurotus ostreatus em garrafas de plástico reutilizado

Dissertação de Mestrado, Tecnologia e Segurança Alimentar, 22 de Junho de 2016, Universidade dos Açores.

Síntese, extração e caracterização de biopolímeros de origem microalgal para desenvolvimento de nanofibras

Pesquisas com microalgas estão crescendo devido aos possíveis bioprodutos oriundos de sua biomassa, bem como as suas diferentes aplicabilidades. Microalgas podem ser cultivadas para a produção de biopolímeros com características de biocompatibilidade e biodegradabilidade. Nanofibras produzidas por electrospinning a partir de poli-β-hidroxibutirato (PHB) geram produtos com aplicabilidade na área de alimentos e médica. O objetivo deste trabalho foi selecionar microalgas com maior potencial para síntese de biopolímeros, em diferentes meios de cultivo, bem como purificar poli-β-hidroxibutirato e desenvolver nanofibras. Este trabalho foi dividido em cinco artigos: (1) Seleção de microalgas produtoras de biopolímeros; (2) Produção de biopolímeros pela microalga Spirulina sp. LEB 18 em cultivo com diferentes fontes de carbono e redução de nitrogênio; (3) Síntese de biopolímeros pela microalga Spirulina sp. LEB 18 em cultivos autotróficos e mixotróficos; (4) Purificação de poli-β- hidroxibutirato extraído da microalga Spirulina sp. LEB 18; e (5) Produção de nanofibras a partir de poli-β-hidroxibutirato de origem microalgal. Foram estudadas as microalgas Cyanobium sp., Nostoc ellipsosporum, Spirulina sp. LEB 18 e Synechococcus nidulans. Os biopolímeros foram extraídos nos tempos de 5, 10, 15, 20 e 25 d de cultivo a partir de digestão diferencial. Para os experimentos com diferentes nutrientes, foi utilizado como fonte de carbono, bicarbonato de sódio, acetato de sódio, glicose e glicerina modificando-se as concentrações de nitrogênio e fósforo. Os cultivos foram realizados em fotobiorreatores fechados de 2 L. A concentração inicial de inóculo foi 0,15 g.L-1 e os ensaios foram mantidos em estufa termostatizada a 30 ºC com iluminância de 41,6 µmolfótons.m -2 .s -1 e fotoperíodo 12 h claro/escuro. Para a purificação de PHB, foi utilizada a biomassa da cianobactéria Spirulina sp. LEB 18, cultivada em meio Zarrouk. Após a extração do biopolímero bruto, a amostra foi desengordurada com hexano e purificada com 1,2-carbonato de propileno. Foram determinadas as purezas e as propriedades térmicas no PHB purificado. O biopolímero utilizado para produzir as nanofibras apresentava 70 % de pureza. A técnica para produção de nanofibras foi o electrospinning. As microalgas que apresentaram máxima produtividade foram Nostoc ellipsosporum e Spirulina sp. LEB 18 com rendimento de biopolímero 19,27 e 20,62 % em 10 e 15 d, respectivamente, na fase de máximo crescimento celular. O maior rendimento de biopolímeros (54,48 %) foi obtido quando se utilizou 8,4 g.L-1 de NaHCO3, 0,05 g.L-1 de NaNO3 e 0,1 g.L-1 de K2HPO4. A condição que proporcionou maior pureza do PHB foi a 130 ºC e 5 min de contato entre o solvente (1,2-carbonato de propileno) e o PHB. As análises térmicas para todas as amostras foram semelhantes em relação ao PHB padrão (Sigma-Aldrich). A purificação com 1,2-carbonato de propileno foi eficiente para o PHB extraído de microalga, alcançando pureza acima de 90 %. A condição que apresentou menores diâmetros de nanofibras foi ao utilizar solução contendo 20 % de biopolímero solubilizado em clorofórmio. As condições do electrospinning que apresentou nanofibras com diâmetros de 470 e 537 nm foram, vazão 150 µL.h-1 , diâmetro do capilar 0,45 mm e voltagens entre 24,1 e 29,6 kV, respectivamente. A microalga Spirulina sp. LEB 18 produz PHB ao utilizar menores concentrações de nutrientes no meio de cultivo, que pode ser purificado com 1,2-carbonato de propileno. Este biopolímero possui aplicabilidade para produção de nanofibras.