Hydrogen adsorption on two-dimensional germanene and its structural defects: an ab initio investigation.

Herein, the adsorption of hydrogen on pristine germanene was studied using ab initio calculations. By performing a converged density functional theory calculation, we have found the nearly degenerate nature of hydrogen at the top sites HT1 and HT2, among which HT1 is the most stable site. The adsorption of a hydrogen atom on germanene led to local structural changes in germanene. To the best of our knowledge, this is the first study on the investigation of the localized surface curvature and zero-point energy of hydrogen for 2D germanene. Moreover, we demonstrated the properties of germanene defects via the four obtained defects: the Stone-Wales (55-77), divacancy (77-555-6), divacancy (555-7), and pentagon-heptagon linear (5-7) defect. The lowest formation energy of the pentagon-heptagon linear defect is shown for the first time in this study.

Recovery of protein hydrolysate and chitosan from black tiger shrimp (Penaeus monodon) heads: approaching a zero waste process.

Shrimp heads are considered as a potential source for the recovery of many valuable components such as chitin, protein and carotenoids. In the present study, both protein hydrolysate and chitin/chitosan were recovered using combination of physical, biological and chemical treatments. Shrimp heads were separated from liquid phase by a facile and efficient physical pretreatment. The liquid fraction was then hydrolyzed using formic acid and vacuum concentrated to obtain an astaxanthin-rich protein hydrolysate. The solid fraction was used to produce chitin by deproteination and demineralization. The hydrolysate consisted of a high astaxanthin (192 ppm) and protein (26.3 wt%) content. Chitosan prepared from chitin showed a high degree of deacetylation (85.4%) with low protein (0.25 wt%) and mineral (0.22 wt%) contents. The relative crystalline structure of the chitin and chitosan were 54.7 and 10.4%, respectively. The deacetylation of chitin was confirmed by Fourier Transform Infrared Spectroscopy. The present procedure approached to produce maximum valuable components including astaxanthin-rich protein hydrolysate and chitin/chitosan from shrimp head waste.

Burden of anemia in relation to thalassemia and iron deficiency among Vietnamese pregnant women.

BACKGROUND AND AIMS: Information about the extent to which anemia is related to thalassemia and iron deficiency (ID) is not available in Vietnam. This study investigated the burden of anemia in relation to thalassemia and ID among Vietnamese pregnant women. METHODS: A cross-sectional study was conducted in Thua Thien Hue, Central Vietnam. Blood samples taken from 399 pregnant women with a gestational age <12 weeks were analyzed. Anemia was defined as Hb levels <11 g/dl, and ID as ferritin values <15 ng/ml. RESULTS: Out of 399 participants, 77 (19.3%) were anemic. While the prevalence of ID was 20.1%, the prevalence of ID anemia was 6.0%. The overall prevalence of thalassemia was 7.3%. Of the 77 anemic women, 24 (31.2%) had ID, and 20 (26.0%) had thalassemia genes. The rest (42.9%) were anemic due to unknown causes. CONCLUSIONS: The results indicate that ID remains a significant health burden among the study population, together with anemia caused by unknown factors. Thalassemias appear not to contribute to a great extent to anemia among Vietnamese pregnant women. Other causes need to be investigated further in order to develop an effective control program for anemia within the population.

New approaches for Artemia pond culture.

A project for intensive culture of Artemia in Vinhchau solar saltwork was funded by Soctrang Authority. The aim of this project is to increase the average cyst yield of 50kg.ha-1.crop, and to build up a stable culture technique with a better yield for local farmers. Multiple laboratory experiments were set up with inert food including fermented rice bran, tiger shrimp feed (PL15), as well as their combination with live algae (Chaetoceros). Results showed that, under laboratory conditions, fermented rice bran and tiger shrimp feed can be used as supplemental food sources. The shrimp feed alone or in combination with algae always gave better cyst production compared to the others, but should not account for more than 50% of the diet. In the field trials, aeration of Artemia ponds also increased cyst yields (from 195.8+/-44.2 to 207+/-46.1kg.ha-1.crop with 6 and 12 aeration a day, respectively) compared to ponds with no aeration (88.2+/-27.5kg.ha-1.crop), however the returns on investment (ROI=2.73-2.71 with aera tion vs. 2.24 without) are not significantly different. Utilization of fermented rice bran (20kg.ha-1.day) and shrimp feed (6kg.ha-1.day) as a supplementary feed during pond production in combination with greenwater supplies (10% of pond volume daily) resulted in higher yields (96.0+/-15.9 and 157.2+/-15.0kg.ha-1.crop, respectively) than traditional culture; Shrimp feed as a supplemental feed supported the cyst yield but their negative effect was at a high cost vs. traditional culture and use of fermented rice bran. Based on the cyst yield and ROI, fermented rice bran should be a promising item for poor farmers.

Swollen-state preparation of chitosan lactate from moulted shrimp shells and its application for harvesting marine microalgae Nannochloropsis sp.

Chitosan lactate (CSS) has been widely used for academic and industrial applications due to its biocompatibility, biodegradability, and high biological activity. Unlike chitosan, which is generally soluble only in acid solution, CSS can be directly used by dissolving in water. In this study, CSS was prepared from moulted shrimp chitosan at room temperature by a solid-state method. Chitosan was first swollen in a mixture of ethanol and water, making it more susceptible to reacting with lactic acid in the next step. As a result, the prepared CSS had a high solubility (over 99 %) and zeta potential (+ 99.3 mV) and was comparable to the commercial product. The preparation method of CSS is facile and efficient for a large-scale process. In addition, the prepared product exhibited a potential flocculant for harvesting Nannochloropsis sp., a marine microalga widely used as a popular food for larvae. In the best condition, the CSS solution (250 ppm) at pH 10 showed the highest recovery capacity (∼ 90 % after 120 min) for harvesting Nannochloropsis sp. Besides, the harvested microalgal biomass showed excellent regeneration after 6 culture days. This paper's findings suggest a circular economy in aquaculture by producing value-added products from solid wastes, which can minimize the environmental impact and move towards sustainable zero-waste.

Phenotypic but no genetic adaptation in zooplankton 24 years after an abrupt +10°C climate change.

The climate is currently warming fast, threatening biodiversity all over the globe. Populations often adapt rapidly to environmental change, but for climate warming very little evidence is available. Here, we investigate the pattern of adaptation to an extreme +10°C climate change in the wild, following the introduction of brine shrimp Artemia franciscana from San Francisco Bay, USA, to Vinh Chau saltern in Vietnam. We use a resurrection ecology approach, hatching diapause eggs from the ancestral population and the introduced population after 13 and 24 years (∼54 and ∼100 generations, respectively). In a series of coordinated experiments, we determined whether the introduced Artemia show increased tolerance to higher temperatures, and the extent to which genetic adaptation, developmental plasticity, transgenerational effects, and local microbiome differences contributed to this tolerance. We find that introduced brine shrimp do show increased phenotypic tolerance to warming. Yet strikingly, these changes do not have a detectable additive genetic component, are not caused by mitochondrial genetic variation, and do not seem to be caused by epigenetic marks set by adult parents exposed to warming. Further, we do not find any developmental plasticity that would help cope with warming, nor any protective effect of heat-tolerant local microbiota. The evolved thermal tolerance might therefore be entirely due to transgenerational (great)grandparental effects, possibly epigenetic marks set by parents who were exposed to high temperatures as juveniles. This study is a striking example of "missing heritability," where a large adaptive phenotypic change is not accompanied by additive genetic effects.

Improved method for production of chitin and chitosan from shrimp shells.

In this study, pretreatment procedures have been investigated preceding the standard production of chitin and chitosan. These steps can be used in industrial processes to preserve raw shrimp shells as long as the amount of material is not enough for one production batch. After these treatments, shrimp shells are clean and are facile for further demineralization, deproteinization and deacetylation processes. The prepared chitin and chitosan show a high purity with very low ash (less than 0.3%) and protein residues (less than 0.5%), along with their high molecular weight and high crystallinity. This modified approach has potential for application in large-scale production due to its ease of operation and reduction of environmental concerns.

Two previously unknown Phytophthora species associated with brown rot of Pomelo (Citrus grandis) fruits in Vietnam.

Two distinct Phytophthora taxa were found to be associated with brown rot of pomelo (Citrus grandis), a new disease of this ancestral Citrus species, in the Vinh Long province, Mekong River Delta area, southern Vietnam. On the basis of morphological characters and using the ITS1-5.8S-ITS2 region of the rDNA and the cytochrome oxidase subunit 1 (COI) as barcode genes, one of the two taxa was provisionally named as Phytophthora sp. prodigiosa, being closely related to but distinct from P. insolita, a species in Phytophthora Clade 9, while the other one, was closely related to but distinct from the Clade 2 species P. meadii and was informally designated as Phytophthora sp. mekongensis. Isolates of P. sp. prodigiosa and P. sp. mekongensis were also obtained from necrotic fibrous roots of Volkamer lemon (C. volkameriana) rootstocks grafted with 'King' mandarin (Citrus nobilis) and from trees of pomelo, respectively, in other provinces of the Mekong River Delta, indicating a widespread occurrence of both Phytophthora species in this citrus-growing area. Koch's postulates were fulfilled via pathogenicity tests on fruits of various Citrus species, including pomelo, grapefruit (Citrus x paradisi), sweet orange (Citrus x sinensis) and bergamot (Citrus x bergamia) as well as on the rootstock of 2-year-old trees of pomelo and sweet orange on 'Carrizo' citrange (C. sinensis 'Washington Navel' x Poncirus trifoliata). This is the first report of a Phytophthora species from Clade 2 other than P. citricola and P. citrophthora as causal agent of fruit brown rot of Citrus worldwide and the first report of P. insolita complex in Vietnam. Results indicate that likely Vietnam is still an unexplored reservoir of Phytophthora diversity.

Preparation and characterization of high purity ß-chitin from squid pens (Loligo chenisis).

Squid pens were extracted by a NaOH solution at 80°C for 10h to remove protein and minerals. The as-prepared ß-chitin had a high molecular weight (8.5±0.1×103kDa), a low protein content (0.63±0.02wt.%), and a negligible amount of minerals. This method avoids the conventional method for the removal of minerals from shrimp and crab shells by HCl. The purity of resulting products was measured by NMR and FTIR. Moreover, the morphology and crystallinity of ß-chitin was characterized by SEM and XRD. The ß-chitin with long chains and high purity is suitable for producing high quantity ß-chitosan for various potential applications.