Elaboration and characterization of bioplastic films based on bitter cassava starch (Manihot esculenta) reinforced by chitosan extracted from crab (Shylla seratta) shells

Bioplastics are polymer plastics which are derived from renewable biomass resources. In this study, bioplastic films based on two different polysaccharides such as bitter cassava starch and chitosan extracted from crab shells were produced by casting technique, using glycerol as plasticizer. The purposes of this research are to characterize and to figure out the effect of additional chitosan concentrations (0; 10; 20; 30; 50% by weight of starch) on the physicochemical, mechanical and water barrier properties of bioplastic films. The film's solubility in water (S), water absorption capacity (WAP), water vapor permeability (WVP), tensile strength (TS), elongation at break (E), Young's modulus (YM) and biodegradability were investigated. The possible interactions between starch and chitosan molecules were evaluated by Fourier transform infrared spectroscopy (FTIR). From the analysis, the incorporation of the chitosan shows improved results on the water barrier properties of the bioplastic films. Optimum solubility in water, water absorption capacity, and water vapor permeability are obtained on the composition of starch/chitosan was 50/50. Actually, the addition of chitosan increased tensile strength, and elongation at break. The characterization of optimum mechanical proprieties also occurred on the 50/50 composition of cassava-starch and chitosan. At this ratio, tensile strength obtained were 6,3000 MPa; and the elongation at break were 62,8571%. It was found that cassava-starch/chitosan-based films have a stable structure compared to native cassava-starch films.Comment: 14 pages, 15 figure

Bacterial diversity of field-caught mosquitoes, Aedes albopictus and Aedes aegypti, from different geographic regions of Madagascar.

peer reviewedSymbiotic bacteria are known to play important roles in the biology of insects, but the current knowledge of bacterial communities associated with mosquitoes is very limited and consequently their contribution to host behaviors is mostly unknown. In this study, we explored the composition and diversity of mosquito-associated bacteria in relation with mosquitoes’ habitats. Wild Aedes albopictus and Aedes aegypti were collected in three different geographic regions of Madagascar. Culturing methods and denaturing gradient gel electrophoresis (DGGE) and sequencing of the rrs amplicons revealed that Proteobacteria and Firmicutes were the major phyla. Isolated bacterial genera were dominated by Bacillus, followed by Acinetobacter, Agrobacterium and Enterobacter. Common DGGE bands belonged to Acinetobacter, Asaia, Delftia, Pseudomonas, Enterobacteriaceae and an uncultured Gammaproteobacterium. Double infection by maternally inherited Wolbachia pipientis prevailed in 98% of males (n = 272) and 99% of females (n = 413); few individuals were found to be monoinfected withWolbachia wAlbB strain. Bacterial diversity (Shannon–Weaver and Simpson indices) differed significantly per habitat whereas evenness (Pielou index) was similar. Overall, the bacterial composition and diversity were influenced both by the sex of individuals and by the environment inhabited by the mosquitoes; the latter might be related to both the vegetation and the animal host populations that Aedes used as food sources.‘Arthropod Symbioses: from fundamental to pest disease management’

Improvement of the growth of Arthrospira (Spirulina) platensis from Toliara (Madagascar): Effect of agitation, salinity and CO2 addition

Arthrospira (Spirulina) platensis Toliara isolated from alkaline and salt lakes in the south-western area of Madagascar is a potential source of proteins that could efficiently fight against food deficiency in developing countries like Madagascar. Up to now, productivity in this country has been low, so a better understanding of the growth conditions of this species is needed to improve its production. Growth experiments were undertaken in bubble columns at laboratory scale. The influence of agitation of the culture, medium salinity (ranging from 13 to 35gL−1) and CO2 addition (ranging from 0 to 2%, v/v) on growth and protein content was examined. Because Arthrospira cells are fragile, a bubble column without additional mixing gave the best growth. Arthrospira (Spirulina) platensis showed higher specific growth rate (μmax) and protein content for lower salinity. Addition of 1% of CO2 improved the productivity by near 60%. The feasability of semi-continuous culture was demonstrated and optimal culture conditions led to a mean productivity of 0.22±0.03gL−1d−1, a mean specific growth rate of 0.015±0.002h−1 and a protein content of 53±2% of total dry weight

Biogeography of the two major arbovirus mosquito vectors, Aedes aegypti and Aedes albopictus (Diptera, Culicidae), in Madagascar

Background: In the past ten years, the Indian Ocean region has been the theatre of severe epidemics of chikungunya and dengue. These outbreaks coincided with a high increase in populations of Aedes albopictus that outcompete its sister taxon Aedes aegypti in most islands sampled. The objective of this work was to update the entomological survey of the two Aedes species in the island of Madagascar which has to face these arboviroses. Methods: The sampling of Aedes mosquitoes was conducted during two years, from October 2007 to October 2009, in fifteen localities from eight regions of contrasting climates. Captured adults were identified immediately whereas immature stages were bred until adult stage for determination. Phylogenetic analysis was performed using two mtDNA genes, COI and ND5 and trees were constructed by the maximum likelihood (ML) method with the gene time reversible (GTR) model. Experimental infections with the chikungunya virus strain 06.21 at a titer of 107.5 pfu/mL were performed to evaluate the vector competence of field-collected mosquitoes. Disseminated infection rates were measured fourteen days after infection by immunofluorescence assay performed on head squashes. Results: The species Aedes aegypti was detected in only six sites in native forests and natural reserves. In contrast, the species Aedes albopictus was found in 13 out of the 15 sites sampled. Breeding sites were mostly found inman-made environments such as discarded containers, used tires, abandoned buckets, coconuts, and bamboo cuts. Linear regression models showed that the abundance of Ae. albopictus was significantly influenced by the sampling region (F = 62.00, p < 2.2 × 10-16) and period (F = 36.22, p = 2.548 × 10-13), that are associated with ecological and climate variations. Phylogenetic analysis of the invasive Ae. albopictus distinguished haplotypes from South Asia and South America from those of Madagascar, but the markers used were not discriminant enough to discern Malagasy populations. The experimental oral infection method showed that six Ae. albopictus populations exhibited high dissemination infection rates for chikungunya virus ranging from 98 to 100%. Conclusion: In Madagascar, Ae. albopictus has extended its geographical distribution whereas, Ae. aegypti has become rare, contrasting with what was previously observed. Changes are predominantly driven by human activities and the rainfall regime that provide suitable breeding sites for the highly anthropophilic mosquito Ae. albopictus. Moreover, these populations were found to be highly susceptible to chikungunya virus. In the light of this study, Ae. albopictus may have been involved in the recent outbreaks of chikungunya and dengue epidemics in Madagascar, and consequently, control measures should be promoted to limit its current expansion.Rôle des moustiques Culicidae, de leurs communautés microbiennes et des réservoirs vertébrés, dans la transmission des arbovirus à Madagasca

The Use of Allochthonous Tropical Peat Swamps of Antananarivo for Dyes Elimination in Effluents

International audienceTextile industries play an important role in the economy of developing countries. However, these industries are among the major consumers of water and chemical inputs. They reject considerable quantities of wastewater, the quality of which sometimes threatens the environment due to the inefficiency of the treatment methods used. This is combined with the inaccessibility to the advanced purification technologies because of their high cost. Many low-cost materials have been studied by scientists to treat effluents. The ATP (allochthonous tropical peat) of Antananarivo, Madagascar, has aroused interest in the treatment of wastewater, especially for colored textile effluents. The physico-chemical characteristics of the ATP are determined, then the BLM dye (methylene blue) is used as a model dye for adsorption. After that, treatment tests in the form of filtration are carried out with textile effluent. This study showed that ATP removes cationic dyes more favorably than anionic ones at pH greater than 4.2, the zero-charge point of peat. The adsorption of BLM, a cationic dye, on ATP is physisorption and endothermic. A maximum of 20mg of BLM dye is adsorbed per gram of ATP and its follows the Langmuir model. The analysis of the IR spectra showed that the carboxylic function and the phenol group of the peat are involved on the dye fixation. The treatment of effluent taken from the textile industry revealed that ATP improves the pH and the color of the effluent; however, it increases the COD due to the presence of certain organic acids

Diversity of culturable bacteria including Pantoea in wild mosquito Aedes albopictus

Background: The microbiota has been shown to play an important role in the biology of insects. In recent decades, significant efforts have been made to better understand the diversity of symbiotic bacteria associated with mosquitoes and assess their influence on pathogen transmission. Here, we report the bacterial composition found in field-caught Aedes albopictus populations by using culture-dependent methods. Results: A total of 104 mosquito imagos (56 males and 48 females) were caught from four contrasting biotopes of Madagascar and their bacterial contents were screened by plating whole body homogenates on three different culture media. From 281 bacterial colony types obtained, amplified ribosomal DNA restriction analysis (ARDRA) showed they had 40 distinct ribotypes. Sequencing and BLAST analysis of the 16S rDNA genes responsible for each representative profile made it possible to identify 27 genera distributed in three major phyla. In female mosquitoes, bacterial isolates were mostly Proteobacteria (51.3%) followed by Firmicutes (30.3%) and Actinobacteria (18.4%). Conversely, Actinobacteria was the most abundant phylum in male mosquitoes (48%) followed by Proteobacteria (30.6%) and Firmicutes (20.4%). The relative abundance and composition of isolates also varied between sampling sites, ranging from 3 distinct families in Ankazobe to 8 in Tsimbazaza Park, and Toamasina and Ambohidratrimo. Pantoea was the most common genus in both females and males from all sampling sites, except for Ambohidratrimo. No differences in genome size were found between Pantoea isolates from mosquitoes and reference strains in pulse field gel electrophoresis. However, according to the numbers and sizes of plasmids, mosquito isolates clustered into three different groups with other strains isolated from insects but distinct from isolates from the environment. Conclusions: The recent upsurge in research into the functional role of the insect microbiota prompts the interest to better explore the role some bacteria detected here may have in the mosquito biology. Future studies of culturable bacteria might decipher whether they have a biological role in the invasiveness of Ae. albopictus. As a possible candidate for paratransgenesis, the predominant genus Pantoea will be characterized to better understand its genetic contents and any possible influence it may have on vector competence of Ae. albopictus.Arthropod Symbioses: from fundamental to pest disease managemen

Efficacy of seed extracts of Annona squamosa and Annona muricata (Annonaceae) for the control of Aedes albopictus and Culex quinquefasciatus (Culicidae)

Objective: To evaluate the potential efficacy of seed extracts of Annona squamosa and Annona muricata used as natural insecticides to control adult and larvae of the vectors Aedes albopictus and Culex quinquefasciatus under laboratory conditions. Methods: Aqueous and oil extracts of the two plants were prepared from dried identifications of the chemical components of each seed extracts were performed using microreactional and GCP Technique. Larvea and adults of Aedes albopictus and Culex quinquefasciatus were collected for the breeding sites in coastal and highlands regions of Madagascar. WHO standardized tests of susceptibility for larvae and imaginal stage of mosquitoes were realized to 50 of mosquitoes. Results: Chemical identifications showed that these extracts contain alkaloids and flavonoids compounds that probably confer their biological insecticidal propriety. CPG analysis showed also the presenceof various fatty acids. On adults mosquitoes, significant insecticidal effects were observed with both aqueous and oil extracts of the two plant seeds compared to mortality induced by deltamethrin, an insecticide used as reference. Extracts of Annona muricata induced high mortality rate to both species of mosquito compared to extracts of Annona squamosa at all concentrations 50 of seed extracts ranged from 1% to 5% for adults and 0.5% to 1% for larvae. Conclusions: The seed extracts of these two plants may be used as mosquito controlling agents and offer a new approach to a less costly, pratical and environmentally friendly control of vector borne diseases.Biodiversité et Développement Durable à Madagasca

Nouvelle répartition géographique des espèces Aedes albopictus et Aedes aegypti (Diptères, Culicidae, Aedinae) à Madagascar

Depuis 2006, Madagascar et les îles avoisinantes de l’Océan Indien ont été victimes d’épidémies sévères de dengue et de chikungunya. Les moustiques Aedes albopictus et Aedes aegypti, vecteurs majeurs de ces arboviroses, sont présents à Madagascar et en particulier dans les régions d’émergence épidémique. En vue d’actualiser les données entomologiques, des campagnes de capture d’adultes et de récoltes de larves ont été menées dans 8 régions sélectionnées selon différents niveaux d’anthropisation. Nos résultats ont démontré des changements importants dans la répartition de ces deux espèces vectrices à Madagascar.Rôle des moustiques Culicidae, de leurs communautés microbiennes et des réservoirs vertébrés, dans la transmission des arbovirus à Madagasca

Influence of light quality and intensity in the cultivation of Spirulina platensis from Toliara (Madagascar) in a closed system

BACKROUND: Spirulina platensis (Toliara, Madagascar) provides a food supplement which can fight against malnutrition and food insufficiency in Madagascar. In this country, the current production from three open basins does not cover the need and presents drawbacks, such as low productivity and possible contamination. So cultivation of S. platensis in a closed photobioreactor opens the possibility of extending this microalgae production. In this study, the influence of colour and intensity of the light on S. platensis growth and protein content was investigated in a bubble column. RESULTS: Growth kinetics were obtained for four colours (green, white, red and blue) and four intensities (400, 800, 1000 and 1200 lux) of light. The influence of light colour on Spirulina growth was discussed. The highest productivity (183.6 mg L-1d-1) and concentration (2643 mg L-1) were obtained for green light at 1200 lux. The protein content was 58 %. CONCLUSION: Using green light allows to improve S. platensis growth. The performances obtained with the closed system are higher than those reported in the literature

The Use of FTIR Spectroscopy as a Tool for the Seasonal Variation Analysis and for the Quality Control of Polysaccharides from Seaweeds

Macroalgae are a potentially novel source of nutrition and biologically active molecules. Proliferative species such as Eucheuma denticulatum, Solieria chordalis (red algae) and Sargassum muticum (brown alga) constitute a huge biomass that can be exploited. In this study, we focus on the extraction of polysaccharides from these three macroalgae species and the characterization of cell wall polysaccharides such as carrageenans, fucoidans and alginates by Fourier Transform Infrared spectroscopy with Attenuated Reflectance Module (FTIR-ATR). The comparison of purified extracts with commercial solutions of fucoidans, alginates or carrageenans shows a strong similarity between the spectra. It demonstrates that the methods of extraction that have been used are also suitable purifying technics. Moreover, it validates infrared spectroscopy as a quick, simple and non-destructive method for the accurate analysis of polysaccharides. The FTIR technique applied to samples collected at different periods of the year allowed us to highlight differences in the composition of fucoidans, alginates and carrageenans. Different classes corresponding to the season can be distinguished by statistical multidimensionnal analysis (Principal Component Analysis) showing that the structure of algal polysaccharides, related to bioactivity, depends on the period of harvest. FTIR results showed that S. chordalis and E. denticulatum possess a dominant type of carrageenan called iota-carrageenan. This type of carrageenan is in the majority when the alga is at maturity in its development cycle. During its growth phase, iota-carrageenan precursors can be detected by FTIR spectra, enabling a better control of the extraction and an application of these compounds in various economic sectors. When the alga E. denticulatum is in its juvenile stage, we found traces of kappa-carrageenan and nu-carrageenan polysaccharides in some extracts