title: Biopolymer foams from Novatein thermoplastic protein and poly(lactic acid)

authors: Walallavita, Anuradha Sammani

subjects: Biopolymer

abstract: Novatein is the only commercial thermoplastic protein made from bloodmeal, a highly denatured protein and a readily available by-product of the meat processing industry. One of the major limitations of Novatein is its hydrophilic nature and loss of plasticizer during processing which leads to poor mechanical properties. To address these issues, Novatein has been blended with another biodegradable polymer with good mechanical properties, polylactic acid (PLA).  

Blending two components can lead to poor mechanical properties of the blend due to weak interfacial adhesion and thermodynamic incompatibility. These problems can be overcome with the use of a compatibilizer which helps to stabilize the interface by coalescence suppression of the dispersed domains. In this work, itaconic anhydride grafted PLA (PLA-g-IA) was chosen as a compatibilizer for Novatein-PLA blends because IA is extremely stable when reacted with proteins and less harmful compared to maleic anhydride. 

Reactive extrusion was used to blend different proportions of Novatein and PLA and the compatibilizing effects of itaconic anhydride was examined. Results showed that fewer agglomerated Novatein particles and less phase separation was visible in the presence of compatibilizer. At 50-50 Novatein/PLA, the absence of compatibilizer produced a dispersed morphology which caused the material to disintegrate in chloroform. Upon the addition of itaconic anhydride, the 50-50 blend stayed intact which was thought to be a result of co-continuous morphology. Incorporating 50 wt.% of PLA-g-IA improved the tensile strength of Novatein by 42% and impact strength by 36%. The effect of compatibilizer was evident in wide-angle x-ray scattering. Three phases were detected in the absence of compatibilizer: crystalline Novatein, amorphous Novatein, and amorphous PLA phases. With compatibilizer, the blend was moving toward two phases: crystalline Novatein, and an amorphous blend of Novatein and PLA. Itaconic anhydride grafted PLA improved miscibility between Novatein and PLA, which lead to the fabrication of Novatein-PLA foams.

Foaming Novatein is a new area of study which has never been investigated before. The foamability of a material depends on the ability of the material to withstand the stretching forces during bubble growth and hold the newly formed cellular structure. The low melt strength of Novatein, however, make it difficult to induce a cellular structure in the proteinous bioplastic. Therefore, the foaming ability of Novatein can be improved by blending with PLA, which can successfully be foamed using a batch process with carbon dioxide as the blowing agent.

Various compositions of Novatein/PLA were batch foamed with and without compatibilizer. Results showed that pure Novatein cannot form a cellular structure at a foaming temperature of 80°C, however, in a blend with 50 wt.% PLA, micro cells formed with a higher cell density (8.44x1021 cells cm-3) and smaller cell sizes (3.36 µm) compared to pure PLA and blends with higher amounts of PLA. A further reduction in cell size and increase in cell density was observed upon the addition of compatibilizer due to the higher crystallinity of grafted PLA. The co-continuous morphology obtained upon the addition of compatibilizer led to the development of foams with more uniform cell sizes, which was stable for cell nucleation even at high temperatures.

text: Biopolymer foams from Novatein thermoplastic protein and poly(lactic acid) Novatein is the only commercial thermoplastic protein made from bloodmeal, a highly denatured protein and a readily available by-product of the meat processing industry. One of the major limitations of Novatein is its hydrophilic nature and loss of plasticizer during processing which leads to poor mechanical properties. To address these issues, Novatein has been blended with another biodegradable polymer with good mechanical properties, polylactic acid (PLA).  

Blending two components can lead to poor mechanical properties of the blend due to weak interfacial adhesion and thermodynamic incompatibility. These problems can be overcome with the use of a compatibilizer which helps to stabilize the interface by coalescence suppression of the dispersed domains. In this work, itaconic anhydride grafted PLA (PLA-g-IA) was chosen as a compatibilizer for Novatein-PLA blends because IA is extremely stable when reacted with proteins and less harmful compared to maleic anhydride. 

Reactive extrusion was used to blend different proportions of Novatein and PLA and the compatibilizing effects of itaconic anhydride was examined. Results showed that fewer agglomerated Novatein particles and less phase separation was visible in the presence of compatibilizer. At 50-50 Novatein/PLA, the absence of compatibilizer produced a dispersed morphology which caused the material to disintegrate in chloroform. Upon the addition of itaconic anhydride, the 50-50 blend stayed intact which was thought to be a result of co-continuous morphology. Incorporating 50 wt.% of PLA-g-IA improved the tensile strength of Novatein by 42% and impact strength by 36%. The effect of compatibilizer was evident in wide-angle x-ray scattering. Three phases were detected in the absence of compatibilizer: crystalline Novatein, amorphous Novatein, and amorphous PLA phases. With compatibilizer, the blend was moving toward two phases: crystalline Novatein, and an amorphous blend of Novatein and PLA. Itaconic anhydride grafted PLA improved miscibility between Novatein and PLA, which lead to the fabrication of Novatein-PLA foams.

Foaming Novatein is a new area of study which has never been investigated before. The foamability of a material depends on the ability of the material to withstand the stretching forces during bubble growth and hold the newly formed cellular structure. The low melt strength of Novatein, however, make it difficult to induce a cellular structure in the proteinous bioplastic. Therefore, the foaming ability of Novatein can be improved by blending with PLA, which can successfully be foamed using a batch process with carbon dioxide as the blowing agent.

Various compositions of Novatein/PLA were batch foamed with and without compatibilizer. Results showed that pure Novatein cannot form a cellular structure at a foaming temperature of 80°C, however, in a blend with 50 wt.% PLA, micro cells formed with a higher cell density (8.44x1021 cells cm-3) and smaller cell sizes (3.36 µm) compared to pure PLA and blends with higher amounts of PLA. A further reduction in cell size and increase in cell density was observed upon the addition of compatibilizer due to the higher crystallinity of grafted PLA. The co-continuous morphology obtained upon the addition of compatibilizer led to the development of foams with more uniform cell sizes, which was stable for cell nucleation even at high temperatures.

year: 2018

title: Adaptations to submarine hydrothermal environments exemplified by the genome of Nautilia profundicola

authors: Campbell, Barbara J.

subjects: hydrothermal environment

abstract: Submarine hydrothermal vents are model systems for the Archaean Earth environment, and some sites maintain conditions that may have favored the formation and evolution of cellular life. Vents are typified by rapid fluctuations in temperature and redox potential that impose a strong selective pressure on resident microbial communities. Nautilia profundicola strain Am-H is a moderately thermophilic, deeply-branching Epsilonproteobacterium found free-living at hydrothermal vents and is a member of the microbial mass on the dorsal surface of vent polychaete, Alvinella pompejana. Analysis of the 1.7-Mbp genome of N. profundicola uncovered adaptations to the vent environment—some unique and some shared with other Epsilonproteobacterial genomes. The major findings included: (1) a diverse suite of hydrogenases coupled to a relatively simple electron transport chain, (2) numerous stress response systems, (3) a novel predicted nitrate assimilation pathway with hydroxylamine as a key intermediate, and (4) a gene (rgy) encoding the hallmark protein for hyperthermophilic growth, reverse gyrase. Additional experiments indicated that expression of rgy in strain Am-H was induced over 100-fold with a 20uC increase above the optimal growth temperature of this bacterium and that closely related rgy genes are present and expressed in bacterial communities residing in geographically distinct thermophilic environments. N. profundicola, therefore, is a model Epsilonproteobacterium that contains all the genes necessary for life in the extreme conditions widely believed to reflect those in the Archaean biosphere—anaerobic, sulfur, H₂- and CO₂-rich, with fluctuating redox potentials and temperatures. In addition, reverse gyrase appears to be an important and common adaptation for mesophiles and moderate thermophiles that inhabit ecological niches characterized by rapid and frequent temperature fluctuations and, as such, can no longer be considered a unique feature of hyperthermophiles.

text: Adaptations to submarine hydrothermal environments exemplified by the genome of Nautilia profundicola Submarine hydrothermal vents are model systems for the Archaean Earth environment, and some sites maintain conditions that may have favored the formation and evolution of cellular life. Vents are typified by rapid fluctuations in temperature and redox potential that impose a strong selective pressure on resident microbial communities. Nautilia profundicola strain Am-H is a moderately thermophilic, deeply-branching Epsilonproteobacterium found free-living at hydrothermal vents and is a member of the microbial mass on the dorsal surface of vent polychaete, Alvinella pompejana. Analysis of the 1.7-Mbp genome of N. profundicola uncovered adaptations to the vent environment—some unique and some shared with other Epsilonproteobacterial genomes. The major findings included: (1) a diverse suite of hydrogenases coupled to a relatively simple electron transport chain, (2) numerous stress response systems, (3) a novel predicted nitrate assimilation pathway with hydroxylamine as a key intermediate, and (4) a gene (rgy) encoding the hallmark protein for hyperthermophilic growth, reverse gyrase. Additional experiments indicated that expression of rgy in strain Am-H was induced over 100-fold with a 20uC increase above the optimal growth temperature of this bacterium and that closely related rgy genes are present and expressed in bacterial communities residing in geographically distinct thermophilic environments. N. profundicola, therefore, is a model Epsilonproteobacterium that contains all the genes necessary for life in the extreme conditions widely believed to reflect those in the Archaean biosphere—anaerobic, sulfur, H₂- and CO₂-rich, with fluctuating redox potentials and temperatures. In addition, reverse gyrase appears to be an important and common adaptation for mesophiles and moderate thermophiles that inhabit ecological niches characterized by rapid and frequent temperature fluctuations and, as such, can no longer be considered a unique feature of hyperthermophiles.

year: 2009

title: What do New Zealand picturebooks tell us about New Zealand national identity?

authors: Daly, Nicola

abstract: Jeffries (2004, p. 4) defines national identity as ' ... a shared sense of belonging of a group of people that depends on a common area of named place, a common set of beliefs and values, and positive feelings for a specific named geographical area'. In her examination of how New Zealand culture is portrayed in picturebooks published between 2000 and 2005, McNeur (2006) suggests that the visual and textual messages in children's picturebooks are an important contributor to the development of children's national identity. This paper describes the process of choosing a collection of 22 New Zealand children's picturebooks (known as the New Zealand PictureBook Collection) to reflect and represent diversity in New Zealand national identity, and analyses what these books tell us about the New Zealand national identity.

text: What do New Zealand picturebooks tell us about New Zealand national identity? Jeffries (2004, p. 4) defines national identity as ' ... a shared sense of belonging of a group of people that depends on a common area of named place, a common set of beliefs and values, and positive feelings for a specific named geographical area'. In her examination of how New Zealand culture is portrayed in picturebooks published between 2000 and 2005, McNeur (2006) suggests that the visual and textual messages in children's picturebooks are an important contributor to the development of children's national identity. This paper describes the process of choosing a collection of 22 New Zealand children's picturebooks (known as the New Zealand PictureBook Collection) to reflect and represent diversity in New Zealand national identity, and analyses what these books tell us about the New Zealand national identity.

year: 2016