Characterization of palm wine yeasts using osmotic, ethanol tolerance and the isozyme polymorphism of alcohol dehydrogenase

Physiologic characteristics of ten palm-wine yeast isolates obtained from nine localities in four provinces in southern Cameroon were assessed using sensitivity to chloramphenicol, tolerance to acetic acid, ethanol tolerance, osmotolerance as well as protein and alcohol dehydrogenase (ADH) polymorphism. None of these isolates was sensitive to 30 ìg/ml chloramphenicol and all were nontolerant to 1% acetic acid. Some of the isolates (Vip 2 and Vip 10) showed tolerance to both high sucrose and ethanol concentrations, criteria which are useful in fermentation. Results indicated that 80% of the strains were able to grow at 15% alcohol solution and only 20% grew on 40% sucrose solution. The denatured protein pattern (SDS-PAGE) as well as the native protein pattern was similar for all strains. The ADH pattern showed a high diversity based on which isolates were differentiated into three patterns. The electrophoretic patterns showed that the ADH pattern was the best criterion for diversity characterisation because of its specificity and variability

Opportunités et contraintes agroforestières de Ricinodendron heudelotii au Cameroun

Ricinodendron heudelotii est une essence endémique des forêts tropicales humides d’Afrique, très prisée pour ses graines comestibles. Sa régénération naturelle reste difficile à cause principalement de la dormance tégumentaire de ses graines. Elle possède de nombreuses vertus ethnobotaniques et d’opportunités agroforestières pour les peuples des forêts du bassin du Congo. Au nombre de ces vertus, on cite des propriétés médicinales, agroalimentaires, agronomiques, écologiques et industrielles. Des programmes de domestication de R. heudelotii sont en cours dans les stations du Centre Mondial de l’Agroforesterie (CMAF) au Cameroun. L’essentiel des travaux déjà réalisés sur cette essence a porté sur ses propriétés ethnobotaniques, l’analyse de la composition chimique de l’huile des graines et sa domestication. Les tentatives de domestication de R. heudelotii se heurtent par ailleurs à diverses contraintes phytosanitaires encore à identifier. Sur la base des observations réalisées en forêts, dans les pépinières et au laboratoire, les dégâts observés seraient d’origine fongique et entomologique. À ce jour, aucun programme de lutte ou d’amélioration génétique n’est envisagé. Pourtant, l’existence de deux sous-espèces (heudelotii et africanum) chez R. heudelotii et d’une espèce apparentée (R. rautanenii) constitue un atout exploitable pour d’éventuels travaux d’amélioration génétique. Cette étude suggère que R. heudelotii pourrait être considérée comme une essence modèle d’avenir pour l’agroforesterie au Cameroun, avec au premier plan un moyen de lutte prometteur contre la pauvreté, et propose quelques pistes de recherche en vue de contribuer au succès des programmes de  domestication de l’espèce. © 2013 International Formulae Group. All rights reserved.Mots clés : Ricinodendron heudelotii, intérêt agroécologique, contraintes agroforestières, amélioration génétique

Occurrence and functioning of phosphate solubilizing microorganisms from oil palm tree (Elaeis guineensis) rhizosphere in Cameroon

Phosphorus replenishment, particularly in smallholder agriculture, remains a challenge as it is mainly fertilizer dependent. While the use of soluble mineral phosphate fertilizers is the obvious best means tocombat phosphate deficiency in Cameroon, their use is limited by their high cost and availability at farmer’s level. This study was aimed at maintaining the fertility of Cameroon soils by biological means,in order to improve agricultural production, using low inputs technology. Isolates were obtained from oil palm tree (Elaeis guineensis) root fragments and rhizospheric soils and their activity in mobilizingphosphate from insoluble sources was evaluated on agar plates and liquid culture media containing sparingly soluble phosphates. At the end of incubation time, it appeared that, phosphate solubilizationresulted from a combined effect of pH decrease of the media and organic acids production. Furthermore, each of the tested isolates was able to produce at least one of the most important organic acids such as citrate, malate and tartrate. Among the ten isolates tested, three were identified as Pseudomonas fluorescens and would be considered as potential biofertilizers

Pseudomonads and symbiotic micro-organisms as biocontrol agents against fungal disease caused by

Experiments were undertaken to assess the antagonistic aptitude of Pseudomonas spp. alone or associated with mycorrhizal fungi on Pythium aphanidermaturm, the causal agent of seedlings dampingoffand stem rot of cowpea (Vigna unguiculata L. Walp). Evaluation was made using selected strains of pseudomonad (Pseudomonas fluorescens, P. putida and Pseudomonas sp.) isolated from V. unguiculata and Solanum tuberosum rhizospheric soils collected in three agroecological zones of Cameroon. Cultures were conducted on agar plates and in liquid media to evaluate the antagonistic capacity of those strains against Pythium aphanidermaturm and to evaluate their biocontrol activity in protecting cowpea plants. The results showed a direct inhibition of the pathogenic fungus by these bacteria. P. fluorescens used alone against Pythium aphanidermaturm, provided a reduction of the disease index from 3.44 to 1.06. When the arbuscular mycorrhizal fungi Glomus deserticola is associated to P. fluorescens, the disease index dropped to 0.13, confirming the synergistic effect of those beneficial micro-organisms

Les microorganismes genetiquement modifies: potentiel et risques pour l\'environment d\'un pays Africain en developpement

No Abstract.Journal of the Cameroon Academy of Sciences Vol. 7 (3) 2008: pp. 149-15

Potential of Cattle Manure Ash to Improve Soil Fertility and Groundnut (Arachis hypogea L.) Growth in the Adamawa Region (Cameroon)

Groundnut (Arachis hypogea L.) production is a key farming activity in Cameroon, since it substantially contributes to human nutrition, economic wealth of farmers and soil fertility. Most cropping systems in sub Saharan Africa are limited by low soil fertility and subjected to the slash-and-burn agriculture. A study was conducted to investigate the potential of cattle manure ash, derived from cooking activities as soil conditioner in order to improve soil fertility and groundnut performances in two sites in the Adamawa region (Cameroon). The results showed that cattle manure ash slightly increased soil pH, soil moisture, SOM, Corg and C/N ratio in amended plots. Cattle manure ash improved nodule weight and increased arbuscular mycorrhizal fungi colonization in one site, that was translated to better N assimilation, and dry weight of both groundnut varieties used in the study. Future studies are needed to evaluate the full potential of cattle manure ash application, alone and/or associated with others organic wastes for sustainable agriculture in the tropics

Potential of Cattle Manure Ash to Improve Soil Fertility and Groundnut (Arachis hypogea L.) Growth in the Adamawa Region (Cameroon)

Groundnut (Arachis hypogea L.) production is a key farming activity in Cameroon, since it substantially contributes to human nutrition, economic wealth of farmers and soil fertility. Most cropping systems in sub Saharan Africa are limited by low soil fertility and subjected to the slash-and-burn agriculture. A study was conducted to investigate the potential of cattle manure ash, derived from cooking activities as soil conditioner in order to improve soil fertility and groundnut performances in two sites in the Adamawa region (Cameroon). The results showed that cattle manure ash slightly increased soil pH, soil moisture, SOM, Corg and C/N ratio in amended plots. Cattle manure ash improved nodule weight and increased arbuscular mycorrhizal fungi colonization in one site, that was translated to better N assimilation, and dry weight of both groundnut varieties used in the study. Future studies are needed to evaluate the full potential of cattle manure ash application, alone and/or associated with others organic wastes for sustainable agriculture in the tropics

Optimisation de la production d'éthanol par les techniques d'hydrolyse de l'amidon de manioc et la fermentation de la levure de bière (Saccharomyces cerevisiae)

Nous avons évalué les paramètres optimum pour la production d'alcool à partir de l'efficacité d'hydrolyse de l'amidon: chimique (HCl), enzymatique (amylase de Aspergillus niger ou de malt) et mixte (chimique et enzymatique). La fermentation alcoolique par la levure de bière est suivie, à travers l'influence du pH, de la température, du substrat et de la durée. La méthode la plus efficace est l'hydrolyse mixte avec 82% à 86% de rendement et la moins efficace est l'hydrolyse chimique avec 31% de rendement. La teneur en alcool augmente avec la concentration en substrat jusqu'à un optimum à 200 g/l. Le rendement le plus élevé pour la production d'alcool est 47,9%. Les conditions les plus favorables sont: 50 g/l de sucre, pH de 6, 30oC et 36 h de fermentation pour une meilleurerentabilité. On peut optimiser ces résultats en utilisant des technologies plus efficaces pour l'hydrolyse de l'amidon. Il vaut mieux produire l'éthanol à partir d'une fermentation contrôlée pour éviter les intoxications provoquées par le méthanol.Mots clés: fermentation alcoolique, Saccharomyces cerevisiae, amidon de manioc, Aspergillus niger, malt, amylases.Optimum parameters suitable for alcohol production were set up. We tested the efficiency of starch hydrolysis using three methods: hydrochloric acid; enzymatic using microbial Aspergillus niger amylases or malt amylases, mixed hydrolysis combining chemical and enzymatic methods. Alcoholic fermentation was assessed using yeast and wort hydrolysis of starch. The pH, temperature, substrate content and duration of the fermentation were studied. The most efficient method is the mixed chemical and enzymatic hydrolysis because it yielded 82 to 86% and the least efficient is chemical hydrolysis which yielded 31% compared to glucose fermentation. Alcohol concentration increased with substrate concentration to an optimum at 200 g/l. The highest alcohol yield was 47.9%. The optimum parameters for alcohol production using yeast were: 150 g/l, pH of 6, 30oC and duration of 36 h for the best profitability. These results could be improved by using more efficient technology for starch hydrolysis and alcohol production through high ethanol and substrate tolerance. The production of ethanol using established technology is recommended in order to avoid methanol intoxication from uncontrolled fermentation.Key words: alcoholic fermentation, Saccharomyces cerevisiae, cassava starch, Aspergillus niger, malt, amylases

Characteristics and germinative potentialities of the seeds of Tetrapleura tetraptera (Shum & Thonn.) Taub. (Mimosaceae) according to their location in the pod

Tetrapleura tetraptera est une Mimosacée arborescente qui possède de grosses gousses indéhiscentes et allongées de 20 à 35 cm de longueur, contenant 14 à 21 graines dures. Ces graines présentent une inhibition à la germination. Deux lots de graines sont utilisés pour étudier leurs caractéristiques et leurs capacités de germination selon leur situation dans la gousse: le lot Soa provenant d'un jeune arbre et le lot Yaoundé provenant d'un arbre âgé. Les résultats montrent que les graines les plus lourdes sont localisées dans la partie médiane (rangs 5-10) de la gousse. La capacité de germination des graines non scarifiées en conditions contrôlées (germination in vitro) varie de 3 % (lot Soa) à 11 % (lot Yaoundé) après 15 jours. Lorsqu'elles sont scarifiées, leur capacité de germination passe à 80-90 %, après 3 jours. La germination des graines est plus homogène et plus rapide dans la zone médiane (80-100 %), comparativement aux extrémités (50-100 %). Par ailleurs, la croissance des plantules en pépinière (phénomène qui mérite d'être examiné de façon plus suivie) semble plus rapide pour les individus de la zone médiane de la gousse