29 research outputs found
Nitrous oxide (N2O) emissions by termites : does the feeding guild matter ?
In the tropics, termites are major players in the mineralization of organic matter leading to the production of greenhouse gases including nitrous oxide (N2O). Termites have a wide trophic diversity and their N-metabolism depends on the feeding guild. This study assessed the extent to which N2O emission levels were determined by termite feeding guild and tested the hypothesis that termite species feeding on a diet rich in N emit higher levels of N2O than those feeding on a diet low in N. An in-vitro incubation approach was used to determine the levels of N2O production in 14 termite species belonging to different feeding guilds, collected from a wide range of biomes. Fungus-growing and soil-feeding termites emit N2O. The N2O production levels varied considerably, ranging from 13.14 to 117.62 ng N2O-N d(-1) (g dry wt.)(-1) for soil-feeding species, with Cubitermes spp. having the highest production levels, and from 39.61 to 65.61 ng N2O-N d(-1) (g dry wt.)(-1) for fungus-growing species. Wood-feeding termites were net N2O consumers rather than N2O producers with a consumption ranging from 16.09 to 45.22 ng N2O-N d(-1) (g dry wt.)(-1). Incubating live termites together with their mound increased the levels of N2O production by between 6 and 13 fold for soil-feeders, with the highest increase in Capritermes capricornis, and between 14 and 34 fold for fungus-growers, with the highest increase in Macrotermes muelleri. Ammoniaoxidizing (amoA-AOB and amoA-AOA) and denitrifying (nirK, nirS, nosZ) gene markers were detected in the guts of all termite species studied. No correlation was found between the abundance of these marker genes and the levels of N2O production from different feeding guilds. Overall, these results support the hypothesis that N2O production rates were higher in termites feeding on substrates with higher N content, such as soil and fungi, compared to those feeding on N-poor wood
The native shrub, Piliostigma reticulatum , as an ecological “resource island” for mango trees in the Sahel
African farmers are increasingly adopting sustainable agricultural practices including use of native shrub intercropping approaches. In one village of Sénégal (near Thiès) it was reported that farmers planted mango (Mangifera indica) seedlings within the canopies of a native shrub (Piliostigma reticulatum). Anecdotal information and qualitative observations suggested that the presence of P. reticulatum promoted soil quality and a competitive advantage for establishing mango plantations. We hypothesized that soil chemical and microbial properties of mango rhizosphere soil growing in the presence of P. reticulatum would be significantly improved over soils associated with mango growing outside the influence of P. reticulatum. The results showed that mango-shrub interplanting significantly lowered pH, and increased arbuscular mycorrhizal fungi (AMF) colonization of mango roots, enzyme activities, and microbial biomass compared to mango alone. Phylogenetic analyses by PCR-denaturing gradient gel electrophoresis (DGGE) showed that community structures of fungi, bacteria, and bacterial genes responsible for denitrification (nirK) of the soil from the rooting zone of the mango-shrub intercropping system were distinct from all other soil outside the influence of P. reticulatum. It is concluded that P. reticulatum enhances soil biological functioning and that there is a synergistic effect of intercropping mango with the native shrub, P. reticulatum, in soil quality with a more diverse community, greater AMF infection rates, and greater potential to perform decomposition and mineralize nutrients
Agricultural use of household compost in Brazzaville market gardening belt
After the finalization of the household filth processing through aerobic fermentation or compostage, which allowed us to get an organic tool, so important in the plant production, the following communication studies the fertilising values of compost from household filth and raw wastes. Conducted in the fields, the study has revelead being successful with positive effects of the burying of compost upon the output of gardenmarket cultivation (in the Brazzaville poor soil). More over, the direct burying of household filth go along with depressive effects mainly on short-cycle vegetative cultivation
Transformation alimentaire du manioc = Cassava food processing
Cet article décrit les différentes phases de mise au point d'une nouvelle technique de rouissage des racines de manioc en sac étanche au gaz sans ajout d'eau. L'objectif est de diminuer la consommation en eau nécessaire pour la préparation des deux aliments principaux transformés au Congo, le foufou et la chikwangue. Pour obtenir un rouissage comparable (pH, durée de fermentation, élimination des composés cyanés, évolution de la microflore lactique) à celui effectué par voie traditionnelle (immersion des racines), il est nécessaire de découper les racines de manioc en tranches de 3 cm avant la mise en sac. Dans ces conditions, le rouissage dure 3 jours et les racines sont suffisamment ramollies pour les transformations en chikwangue ou foufou. Cependant, pour l'obtention d'un foufou apprécié par les consommateurs, les racines fermentées doivent être rincées, pour diminuer la concentration en acides organiques. L'eau de rinçage peut être réutilisée 3 fois sans altérer les qualités du produit final. Des études sont en cours pour évaluer les qualités organoleptiques de la chikwangue obtenue avec des racines rouies selon cette technique. Cette nouvelle méthode de rouissage peut être appliquée à des régions où la disponibilité en eau est limitée. (Résumé d'auteur
Microbiological and Biochemical Characterization of Cassava Retting, a Traditional Lactic Acid Fermentation for Foo-Foo (Cassava Flour) Production
The overall kinetics of retting, a spontaneous fermentation of cassava roots performed in central Africa, was investigated in terms of microbial-population evolution and biochemical and physicochemical parameters. During the traditional process, endogenous cyanogens were almost totally degraded, plant cell walls were lysed by the simultaneous action of pectin methylesterase and pectate lyase, and organic acids (C(inf2) to C(inf4)) were produced. Most microorganisms identified were found to be facultative anaerobes which used the sugars (sucrose, glucose, and fructose) present in the roots as carbon sources. After 24 h of retting, the fermentation reached an equilibrium that was reproducible in all the spontaneous fermentations studied. Lactic acid bacteria were largely predominant (over 99% of the total flora after 48 h) and governed the fermentation. The epiphytic flora was first replaced by Lactococcus lactis, then by Leuconostoc mesenteroides, and finally, at the end of the process, by Lactobacillus plantarum. These organisms produced ethanol and high concentrations of lactate, which strongly acidified the retting juice. In addition, the rapid decrease in partial oxygen pressure rendered the process anaerobic. Strict anaerobes, such as Clostridium spp., developed and produced the volatile fatty acids (mainly butyrate) responsible, together with lactate, for the typical flavor of retted cassava. Yeasts (mostly Candida spp.) did not seem to play a significant role in the process, but their increasing numbers in the last stage of the process might influence the flavor and the preservation of the end products
Gut-specific actinobacterial community structure and diversity associated with the wood-feeding termite species, Nasutitermes corniger (Motschulsky) described by nested PCR-DGGE analysis
This comprehensive survey studied the actinobacterial community structure and putative representative members associated with the gut of the wood-feeding termite, Nasutitermes corniger (Motschulsky), using nested PCR-DGGE and 16S rDNA sequences analyses. The closest relatives of the actinobacteria inhabiting the gut of Nasutitermes corniger were in five families, regardless of the geographical origin of the termite colony: Propionibacteriaceae, Streptomycetaceae, Cellulomonodaceae, Corynebacteriaceae and Rubrobacteraceae. Feeding termites on beech wood did not result in substantial changes in the actinobacterial community structure as revealed by DGGE banding patterns. Most of the 16S rDNA sequences obtained after excision and sequencing of DGGE bands clustered with those previously retrieved in termite guts. These results confirm the presence of gut-specific actinobacteria. Except for the 16S rDNA sequences affiliated to Streptomycetaceae and Cellulomonodaceae, no sequence had more than 97% similarity with the closest isolated strains, indicating the presence of microorganisms that have not yet been cultivated. These results suggest that members of the Actinomycetales order account for the largest proportion of the Actinobacteria phylum inhabiting the gut of the termite N. corniger