Distribution Of Granules Research Articles

Influence of spatial structure on properties of rice kernel as compared with its flour and starch in limited water

Insight into the architecture and the interaction between components in fully mature rice are difficult to study but are important to its processing technology and quality control as it is mainly consumed as the whole kernel. In this study, different microscopy techniques were combined to explain the differences of rheological and thermal properties between rice kernel and its flour even though they had the same compositions. The area and positions of the endothermic peaks of starch, flour, and kernel were different. The uneven distribution of starch granules and part of the protein bodies were observed by a scanning electron microscope. The regional distribution and spatial structure of starch granules and cell walls showed the restriction effect of kernel structure of rice. The clear fluorescence by a confocal laser scanning microscope showed that the protein bodies and cell walls formed barriers in rice to delay the hydration and limit the expansion of starches. Overall, the structural form of rice is closely related to its physicochemical properties.

Exposure to aristolochic acid I compromises the maturational competency of porcine oocytes via oxidative stress-induced DNA damage.

Aristolochic acid (AA) is a class of carcinogenic and nephrotoxic nitrophenanthrene carboxylic acids naturally found in Aristolochia plants. These plants have been widely used as herbal medicines and also enter the human food chain as the persistent soil pollutants. It has been known that AA exposure is implicated in multiple cancer types, kidney failure and ovarian dysfunction. However, whether AA exposure would influence the oocyte quality has not yet determined. Here, we document that AAI has the negative effects on the competency of oocyte maturation and fertilization. We show that AAI exposure leads to the oocyte meiotic failure via impairing the meiotic apparatus, displaying a prominently defective spindle assembly, actin dynamics and mitochondrial integrity. AAI exposure also causes the abnormal distribution of cortical granules and ovastacin, which is consistent with the observation that fewer sperm bound to the zona pellucida surrounding the unfertilized AAI-exposed eggs, contributing to the fertilization failure. In addition, AAI exposure induces the increased levels of ROS, DNA damage and early apoptosis in porcine oocytes. Collectively, we demonstrate that AAI exposure perturbs the oocyte meiotic progression and fertilization capacity via disruption of both nuclear maturation and cytoplasmic maturation of oocyte, which might be caused by the excessive oxidative stress-induced DNA damage and apoptosis.

N-acetyl-L-cysteine (NAC) delays post-ovulatory oocyte aging in mouse.

The quality of post-ovulatory oocytes decreases with aging. In this study, we aimed to investigate the effects of N-acetyl-L-cysteine (NAC), a broadly used antioxidant, on oocyte quality in mouse post-ovulatory oocyte aging in vitro. NAC at 0.6mM concentration was added to culture medium (M2), and the quality of oocytes was analyzed at 6h, 12h, 18h and 24h of culture. We found that the frequency of spindle defects decreased in NAC-treated oocytes compared to those without NAC treatment. NAC treatment significantly decreased abnormal distribution of cortical granules (CGs) in oocytes during aging for 18h and 24h. Decreased intracellular reactive oxygen species (ROS) was also observed. Increased intracellular ATP levels and decreased abnormal distribution of mitochondria could be observed with NAC supplementation during post-ovulatory oocyte aging in vitro. These results indicate that NAC will maintain the quality of oocytes, and delay post-ovulatory oocyte aging as studied in the mouse.

Brefeldin A impairs porcine oocyte meiotic maturation via interruption of organelle dynamics.

Brefeldin A (BFA) is a lactone antibiotic synthesized from palmitic acid by several fungi that could block anterograde transport of proteins from endoplasmic reticulum to Golgi apparatus by reversible disruption of the Golgi complex. Previous investigations have shown that BFA induces the apoptosis of cancer cells in mitosis and impairs asymmetric spindle positioning in meiosis. Here, we document that exposure to BFA in porcine oocytes compromises the meiotic maturation via disrupting both nuclear and cytoplasmic maturation. We found that BFA exposure collapsed the cytoskeleton assembly by showing the aberrant spindle organization with misaligned chromosomes and defective actin dynamics. Furthermore, the distribution of both mitochondria and cortical granules (CGs), two important indexes of cytoplasmic maturation of oocytes, was disturbed following BFA exposure. We finally validated that the localization of ovastacin, a component of CGs that is essential for the postfertilization removal of sperm-binding sites in the zona pellucida, was also perturbed in BFA-exposed oocytes, which might weaken their fertilization capacity. Collectively, these findings indicate that Golgi-mediated protein transport is indispensable for the porcine oocyte meiotic maturation.

Feedforward and Feedback Control of a Pharmaceutical Coating Process.

This work demonstrates the use of a combination of feedforward and feedback loops to control the controlled release coating of theophylline granules. Feedforward models are based on the size distribution of incoming granules and are used to set values for the airflow in the fluid bed processor and the target coat weight to be applied to the granules. The target coat weight of the granules is controlled by a feedback loop using NIR spectroscopy to monitor the progress of the process. By combining feedforward and feedback loops, significant variation in the size distributions and ambient conditions were accommodated in the fluid bed coating of the granules and a desired dissolution profile was achieved. The feedforward component of the control system was specifically tested by comparing the performance of the control system with and without this element by Monte Carlo simulation.

Process mineralogy as a key factor affecting the flotation kinetics of copper sulfide minerals

The aim of this study is to apply process mineralogy as a practical tool for further understanding and predicting the flotation kinetics of the copper sulfide minerals. The minerals’ composition and association, grain distribution, and liberation within the ore samples were analyzed in the feed, concentrate, and the tailings of the flotation processes with two pulp densities of 25wt% and 30wt%. The major copper-bearing minerals identified by microscopic analysis of the concentrate samples included chalcopyrite (56.2wt%), chalcocite (29.1wt%), covellite (6.4wt%), and bornite (4.7wt%). Pyrite was the main sulfide gangue mineral (3.6wt%) in the concentrates. A 95% degree of liberation with d80 > 80 µm was obtained for chalcopyrite as the main copper mineral in the ore sample. The recovery rate and the grade in the concentrates were enhanced with increasing chalcopyrite particle size. Chalcopyrite particles with a d80 of approximately 100 µm were recovered at the early stages of the flotation process. The kinetic studies showed that the kinetic second-order rectangular distribution model perfectly fit the flotation test data. Characterization of the kinetic parameters indicated that the optimum granulation distribution range for achieving a maximum flotation rate for chalcopyrite particles was between the sizes 50 and 55 µm.

The Chewable Tablet of Guava Leaves Extract (Psidium guajava L.) with Breadfruit Starch as Binder

Breadfruit starch can be used as a binder on the chewable tablet because it consists of amylose and amylopectin which can increase the cohesiveness and make a good bond with the powder. Guava leaves extract can kill the bacterial growth of Streptococcus mutans so it can be served to prevent dental caries. This research aimed to know whether increased concentrations of breadfruit starch can affect the physical characteristics of the chewable tablet of guava leaves extract. The chewable tablets were formulated into 4 formulas with different concentration of mucilago breadfruit starch, such as 10%, 13%, 16% and 19%. Breadfruit starch as a binder obtained from an almost ripe the breadfruit and then was crushed and soaked to occur separation between water immersion and amylum, and then amylum was dried and made as mucilago and the mucilago was added into the formula. The result of the characteristic of starch, the powder was true breadfruit starch. The flowability and particle size distribution of granule was evaluated. Then, the granule was made into the chewable tablet. The research result showed that the increase of mucilago breadfruit starch concentration increased the hardness and decreased friability of chewable tablet.

SIRT2 Inhibition Results in Meiotic Arrest, Mitochondrial Dysfunction, and Disturbance of Redox Homeostasis during Bovine Oocyte Maturation.

SIRT2, a member of the sirtuin family, has been recently shown to exert important effects on mitosis and/or metabolism. However, its roles in oocyte maturation have not been fully clarified. In this study, SIRT2, located in the cytoplasm and nucleus, was found in abundance in the meiotic stage, and its expression gradually decreased until the blastocyst stage. Treatment with SIRT2 inhibitors resulted in the prevention of oocyte maturation and the formation of poor-quality oocytes. By performing confocal scanning and quantitative analysis, the results showed that SIRT2 inhibition induced prominent defects in spindle/chromosome morphology, and led to the hyperacetylation of α-tubulin and H4K16. In particular, SIRT2 inhibition impeded cytoplasmic maturation by disturbing the normal distribution of cortical granules, endoplasmic reticulum, and mitochondria during oocyte meiosis. Meanwhile, exposure to SirReal2 led to elevated intracellular reactive oxygen species (ROS) accumulation, low ATP production, and reduced mitochondrial membrane potential in oocytes. Further analysis revealed that SIRT2 inhibition modulated mitochondrial biogenesis and dynamics via the downregulation of TFAM and Mfn2, and the upregulation of DRP1. Mechanistically, SIRT2 inhibition blocked the nuclear translocation of FoxO3a by increasing FoxO3a acetylation, thereby downregulating the expression of FoxO3a-dependent antioxidant genes SOD2 and Cat. These results provide insights into the potential mechanisms by which SIRT2-dependent deacetylation activity exerts its effects on oocyte quality.

Morphology and Molecular Phylogeny of Two New Terrestrial Ciliates, Australocirrus rubrus n. sp. and Notohymena gangwonensis n. sp. (Ciliophora: Oxytrichidae), from South Korea.

Two new soil oxytrichids, Australocirrus rubrus n. sp. and Notohymena gangwonensis n. sp., were discovered from South Korea. Morphologically, A.rubrus shares many features with A.australis, and these two species form a single clade in a molecular tree based on nuclear small subunit ribosomal RNA (SSU rRNA) gene sequences. Australocirrus rubrus mainly differs from A.australis in the color (citrine color vs. reddish) and distribution of the cortical granules. Additionally, we confirm that the genus Australocirrus is not a monophyletic group, as A.shii is separated from the clade comprising the other Australocirrus species, being clustered instead with other taxa. Notohymena gangwonensis n. sp. mainly differs from its congeners by the following combination of features: irregularly distributed cortical granules (vs. arranged in groups associated with cirri and dorsal kineties), variable four or five (usually four) transverse cirri (vs. invariable five), and the anteriormost pretransverse cirrus V/2 on 13.2-16.1% of cell length (vs. on or above 18.9% of cell length). Currently, there are no available gene sequences for members of the genus Notohymena, thus we provide SSU rRNA gene sequences from the new species of Notohymena, as well as detailed morphological descriptions of the novel species.

Settling velocity and size distribution measurement of anaerobic granular sludge using microscopic image analysis

Settling velocity and size distribution of anaerobic granular sludge samples were studied using microscopic image analysis and settling column experiments. Five granule samples were considered in this study. Three samples were collected at the Top, Middle and Bottom sections of a lab scale upflow anaerobic sludge bed reactor (UASB). Two other granule samples were obtained from industries. This paper aims to establish a method that uses microscopic image analysis and shape factor as a tool to determine the size distribution and settling velocity of anaerobic granules. Image analysis technique was used to calculate the shape factor and equivalent diameter of granules. The equivalent diameter was then used to calculate the theoretical settling velocities based on Allen's formula and estimate size distributions.The results showed that there was a good agreement between the theoretical and experimental mean settling velocity values. Both measured and calculated settling velocities increased with increasing Reynolds number (Re). However, the agreement between measured and calculated values was found to be weaker at higher Re values. Size distribution analyses of the granules have revealed that there was significant difference in the size distribution of granule samples collected at different heights of the lab scale reactor. Overall, granules from the bottom section of the reactor had larger diameter, settling velocity and shape factor than those at the middle and top section granules. Whereas granules collected from the top section exhibited the smallest granular diameter, settling velocity and shape factor.

Deletion of BSG1 in Chlamydomonas reinhardtii leads to abnormal starch granule size and morphology

Chlamydomonas reinhardtii represents an ideal model microbial system to decipher starch metabolism. In this green algae, in cells growing in photosynthetic conditions, starch mainly accumulates as a sheath surrounding the pyrenoid while in cells subjected to a nutrient starvation, numerous starch granules are filling up the plastid stroma. The mechanisms underlying and regulating this switch from photosynthetic to storage starch metabolisms are not known. In this work, we have isolated a Chlamydomonas mutant strain containing a deletion in chromosome 2 which displays abnormal starch granule distribution. Under nitrogen starvation, this strain contains an additional starch granules population. These granules are twice as big as the wild-type granules and display characteristics of photosynthetic starch. Genetic and functional complementation analyses allowed us to identify the gene responsible for this original phenotype which was called BSG1 for “Bimodal Starch Granule”. Possible roles of BSG1 in starch metabolism modifications during the transition from photosynthetic to starved growth conditions are discussed.

Effects of porcine granulocyte-macrophage-colony-stimulating factor on porcine cumulus-oocyte complex maturation in vitro

Introduction: The in vitro maturation (IVM) of oocytes is an essential step in the in vitro embryo production. This study aimed to improve the efficacy of IVM by supplementing with granulocytemacrophage colony stimulating factor (GM-CSF) in the culture medium.
 Methods: The combinatorial effects of GM-CSF and porcine follicular fluid (pFF) were also investigated in porcine cumulusoocyte complex (COC) models. COCs were obtained by aspirating follicles with an 18 G needles. Small and medium follicles were used in this study. COCs from two kinds of follicles were divided into 13 groups to investigate the maturation of COCs at different concentrations of pFF (0, 10%) and GM-CSF (0, 2, 10, 20 ng/mL). The maturation of COCs was evaluated by different variables including cumulus expansion, the appearance of the first polar body, lipid droplet localization, mitochondrial distribution, and cortical granule distribution.
 Results: The results showed that GM-CSF improves the cumulus expansion, and stimulate the mitochondrial and cortical granule movement. However, GM-CSF did not increase nuclear maturation or lipid droplet localization rates in the porcine oocyte.
 Conclusion: In conclusion, porcine GM-CSF had some positive effects on the porcine oocyte maturation.

Starch Granules Size Distribution of Sweet Potato and Their Relationship with Quality of Dried and Fried Products

To understand the quality characteristics of different varieties of starch granules from sweet potato and their relationship with processing adaptability, 21 typical sweet potato varieties cultivated at Zhejiang A&F University are used to study grain size using a Mastersizer 3000 laser particle size analyzer. Our results are as follows: 1) The volume distribution of starch granules is a bimodal curve and the grain size is 2.27 μm. Starch granules with a particle size 17.51 μm are defined as large starch granules. 2) The contents of total starch, amylose, and amylopectin are negatively correlated with the volume percentage of middle‐sized (r = −0.611**, −0.489**, and −0.529**) starch granules but positively correlated with large‐sized (r = 0.628**, 0.544**, and 0.517**) starch granules. 3) In processing applications of sweet potato, the cohesiveness of dried sweet potato is improved and hardness of dried sweet potato decreases with the increase of small‐ and medium‐sized starch granules content. The color, fragrance, exterior, and taste of sweet potato chips are improved with the increase of small‐ and medium‐sized starch granule content. Above results could help understand relationships between granule size and final product quality.

Morphological and molecular characterization of Neogastrostyla aqua nov. gen., nov. spec. (Ciliophora, Hypotrichia) from River Yamuna, Delhi; comparison with Gastrostyla-like genera

A novel hypotrichous ciliate, Neogastrostyla aqua nov. gen., nov. spec. isolated from River Yamuna, Delhi, India, is described using morphological, morphometric and morphogenetic characters from live and stained cells supplemented with derivation of phylogenetic relationships using SSU rRNA gene. Neogastrostyla aqua nov. gen., nov. spec., is characterized by light yellow cortical granules present singly or in clusters of two to five, distributed randomly; parental adoral zone of membranelles retained unchanged for proter; Oxytricha-pattern of paroral and endoral; 25–27 frontal-ventral-transverse cirri including a distinct bipartite frontoventral row of composite origin; three dorsal kineties with no fragmentation of the third kinety, two dorsomarginal kineties, three caudal cirri, two macronuclear nodules and two or three micronuclei. Though Neogastrostyla aqua nov. gen., nov. spec. has a frontoventral row like Gastrostyla species, it differs distinctly in the combination of characters from Gastrostyla and other genera with Gastrostyla-like ventral ciliature (Protogastrostyla, Hemigastrostyla, Apogastrostyla and Pseudogastrostyla) particularly in the colour and distribution of cortical granules as well as arrangement and formation of ciliature. According to the phylogenetic analyses, Neogastrostyla aqua nov. gen., nov. spec. clustered consistently with Gastrostyla sp. Y2 (no description available), Oxytricha granulifera and Architricha indica as close neighbours.

Defective exocytosis and processing of insulin in a cystic fibrosis mouse model.

Cystic fibrosis-related diabetes (CFRD) is a common complication for patients with cystic fibrosis (CF), a disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). The cause of CFRD is unclear, but a commonly observed reduction in first-phase insulin secretion suggests defects at the beta cell level. Here we aimed to examine beta- and alpha-cell function in the Cftrtm1EUR/F508del mouse model (C57BL/6J), which carries the most common human mutation in CFTR, the F508del mutation. CFTR expression, beta cell mass, insulin granule distribution, hormone secretion and single cell capacitance changes were evaluated using islets (or beta cells) from F508del mice and age-matched wild-type mice aged 7-10 weeks. Granular pH was measured with DND-189 fluorescence. Serum glucose, insulin and glucagon levels were measured in vivo, and glucose tolerance was assessed using IPGTT. We show increased secretion of proinsulin and concomitant reduced secretion of C-peptide in islets from F508del mice compared to WT mice. Exocytosis and number of docked granules was reduced. We confirmed reduced granular pH by CFTR stimulation. We detected decreased pancreatic beta cell area, but unchanged beta cell number. Moreover, the F508del mutation caused failure to suppress glucagon secretion leading to hyperglucagonemia. In conclusion, F508del mice have beta cell defects resulting in 1) reduced number of docked insulin granules and reduced exocytosis, and 2) potential defective proinsulin cleavage and secretion of immature insulin. These observations provide insight into the functional role of CFTR in pancreatic islets and contribute to increased understanding of the pathogenesis of CFRD.

Genome-Wide Analysis of Watermelon HSP20s and Their Expression Profiles and Subcellular Locations under Stresses.

Watermelon (Citrullus lanatus L.), which is an economically important cucurbit crop that is cultivated worldwide, is vulnerable to various adverse environmental conditions. Small heat shock protein 20s (HSP20s) are the most abundant plant HSPs and they play important roles in various biotic and abiotic stress responses. However, they have not been systematically investigated in watermelon. In this study, we identified 44 watermelon HSP20 genes and analyzed their gene structures, conserved domains, phylogenetic relationships, chromosomal distributions, and expression profiles. All of the watermelon HSP20 proteins have a conserved the α-crystallin (ACD) domain. Half of the ClHSP20s arose through gene duplication events. Plant HSP20s were grouped into 18 subfamiles and a new subfamily, nucleo-cytoplasmic XIII (CXIII), was identified in this study. Numerous stress- and hormone-responsive cis-elements were detected in the putative promoter regions of the watermelon HSP20 genes. Different from that in other species, half of the watermelon HSP20s were repressed by heat stress. Plant HSP20s displayed diverse responses to different virus infections and most of the ClHSP20s were generally repressed by Cucumber green mottle mosaic virus (CGMMV). Some ClHSP20s exhibited similar transcriptional responses to abscisic acid, melatonin, and CGMMV. Subcellular localization analyses of six selected HSP20- green fluorescence protein fusion proteins revealed diverse subcellular targeting. Some ClHSP20 proteins were affected by CGMMV, as reflected by changes in the size, number, and distribution of fluorescent granules. These systematic analyses provide a foundation for elucidating the physiological functions and biological roles of the watermelon HSP20 gene family.

136 Efficient in vitro embryo production system using in vivo-matured oocytes from superstimulated Japanese black cows

In this study, we examined whether in vivo matured oocytes collected by ovum pickup (OPU) from superstimulated Japanese black cows can improve the productivity and quality of in vitro-produced embryos. Cows in the stimulated group received an intravaginal progesterone-releasing device (Day 0), administration of 100μg of GnRH on Day 5, a single administration of 30 Armour units of FSH on the evening of Day 8 and prostaglandin F2α on the evening of Day 10. The progesterone device was removed on the morning of Day11, and then 100μg of GnRH was administered on the morning of Day 12 (0 h). The OPU and IVF were conducted at 25~26 and 30h, respectively. Cows in the control group received no treatment before OPU, and collected oocytes were subjected to in vitro maturation followed by IVF. The cortical granules distribution of oocytes at metaphase II stage, the cleavage pattern of embryos at the first cell cycle, the developmental rate, and the quality of blastocysts were compared between the stimulated and control groups. Oocytes with cortical granules distributing cortical cytoplasm were classified as normal distribution. The cleavage pattern was evaluated at 28h after IVF as follows: embryos with blastomeres of the same size without fragmentation were classified as normal cleavage; embryos with 2 blastomeres and several small fragments, direct cleavage from the one-cell stage to 3 or 4 blastomeres, or 2 blastomeres of different size were classified as abnormal cleavage. The developmental rate to blastocyst stage was measured on Day 9 of culture. The morphological quality of blastocysts was evaluated based on the IETS manual. All data were obtained from more than 3 replicates. In vitro development and cortical granules distribution data were analysed using chi-squared test. Other data were analysed using Student’s t-test. Normal cortical granules distribution rate in the stimulated group was higher than that in the control group (90.3v. 23.1%; P<0.01). Although no differences in the developmental rate to blastocyst stage (51.5v. 58.6%) was observed, the normal cleavage rate (73.4v. 51.2%) and the transferable embryo rate (98.3v. 88.0%) in the stimulated group were significantly higher (P<0.01) than those in the control group. The ratio of embryos from normal cleavage among the transferable embryos in the stimulated group was also significantly higher than in the control group (82.2v. 57.2%; P<0.01). In addition, the freezable embryo ratio (71.7v. 58.1%; P<0.072) and the total production number of embryos per head (28.0v. 15.5; P<0.106) showed a tendency to be higher in the stimulated group than in the control group. These results suggest that high quality embryos can be efficiently produced by the use of in vivo matured oocytes collected by OPU from superstimulated Japanese black cows.

Study on the Role of Histochemical Stains in Identifying Merkel Cells in Dogs.

Merkel cells (MCs) are neuroendocrine cells involved with tactile sense, growth, differentiation, and homeostasis of the skin as well as in different cutaneous diseases. Specific staining techniques are required for their identification because they are not easily visible in paraffin sections stained with hematoxylin and eosin. The present study assess the histochemical features of the MCs in dogs comparing with those described for other mammals in the literature and with the use of immunohistochemistry. A systematic study of samples from MCs-rich areas from healthy dogs was carried out by use of several histologic stains, including metachromatic staining, silver stains, methylene blue, periodic acid-Schiff stain, and osmium-based staining method. MCs were detected by the Grimelius argyrophilic stain in 86.7% of the specimens. The staining was showed as dark-brown granular cytoplasmic and consistently polarized to the basal cell cytoplasm matching with the cellular distribution of the characteristic neurosecretory granules. Some modifications in the standard staining protocol, including rinsing, silver reimpregnation, and counterstain dye, enhanced the MCs identification in stratified squamous epithelium. When compared with Cytokeratin 20-immunolabeled serial sections several MCs appeared nonstained with the argyrophilic method. These differences in MC numbers between stains were statistically significant. Other histologic stains failed to identify MCs in the specimens. The results of this study indicate that Grimelius argyrophilic stain is a suitable method for demonstration of MCs in the stratified squamous epithelium of skin and mucosa. Discussion on its utility when compared with immunohistochemistry and a review of the scientific literature is also presented. Anat Rec, 302:1458-1464, 2019. © 2018 Wiley Periodicals, Inc.

Application of intracytoplasmic sperm injection to the embryo production in aged cows.

Reduction in oocyte quality is a major factor responsible for declining fertility associated with maternal aging in cows. The objective of the present study was to determine whether intracytoplasmic sperm injection (ICSI) could increase the efficiency of embryo production in older cows. We used cows aged 30 to 50 months or >120 months, which were defined as young or aged, respectively. The distribution of cortical granules in oocytes was affected by age as older cows had lower proportion of oocytes with mature cytoplasm containing evenly dispersed cortical granules compared to young cows. Although fertilization rates did not differ significantly between the two groups after in vitro fertilization (IVF), the rate of abnormal fertilization was higher, and the numbers of total and diploid blastocysts were lower for aged cows compared to young cows. However, in the embryos produced by ICSI, there was no significant difference in these parameters between young and aged cows. Although ICSI did not improve the blastocyst development rate, ICSI increased the proportion of diploid blastocysts in aged cows compared to IVF. In conclusion, maternal aging may negatively affect cytoplasmic maturation of bovine oocytes, which could be associated with abnormal fertilization or low developmental competence of oocytes. Our data also suggests beneficial effects of ICSI on the production of chromosomally normal embryos in aged cows.

Preparation and characterization of thermoplastic starch composite reinforced by plasma-treated poly (hydroxybutyrate) PHB

The present work aims to study the effect of the addition of poly (hydroxybutyrate) PHB as reinforcement in thermoplastic cornstarch (TPS) produced by the thermal compression molding method. Initially, the physical and chemical properties of TPS with different amounts of glycerol as the plasticizer (25, 30 and 35 wt%), are evaluated. Then, the composites, including 35% glycerol and different PHB contents (10, 20 and 30 wt%), are prepared. Additionally, the surface of the PHB granules is modified by plasma treatment using atmospheric air and sulfur hexafluoride (SF6) gas. In order to evaluate the influence of the PHB contents before and after the plasma treatment, the composites are characterized by FTIR, TGA, DSC, XRD, SEM, and mechanical tests. SEM showed a homogeneous distribution of PHB granules in the TPS matrix. On the other hand, the micrographs of the composites, using the high concentration of plasma-treated PHB, showed the agglomerated particles in the starch matrix, which represented stress concentrators, and showed weak interfacial adhesion leading to the poor mechanical properties. The thermogravimetric analysis of the composites with PHB treated by plasma showed a higher thermal stability compared to the composites of TPS and untreated PHB.