In Burkina Faso, deficiency of amino acids in protein is becoming a major healthy public problem. This study was purposed to optimize essentials amino acids in single cell protein (SCP) by supplementing different nitrogen sources during fermentation of mango waste with Candida utilis FJM12. Analytical methods were used to determine biomass yield, chemical composition and amino acids profile of SCP. The principal component analysis (PCA) method was performed to identify the nitrogen source which exhibited best rate of SCP. The maximum biomass yield (6.48±0.03 g/L) exhibited 9.65±0.36% (w/w) of ash, while using yeast extract. The proximate composition of SCP revealed 56. 40±1.30, 13.25±0.11, 3.80±0.10 and 6.60±0.25% (w/w), respectively for crude protein, lipids, carbohydrates, and nucleic acid content. PCA showed a strong correlation between yeast extract and ammonium sulphate and demonstrated their positive influence to increase the rate of SCP and essentials amino acids as compared to Food and Agriculture Organization (FAO) recommendation. These results demonstrated that C. utilis FJM12 could be suitable for essentials amino acids.

Environmental pollution can have detrimental effects on crop yield and its consumers. The current study was designed to investigate the potential human health risks associated with the consumption of lettuce crop contaminated with toxic heavy metals and microbiological status. Irrigated water, soil and lettuce were analyzed by AAS technics for heavy metals including Cd, Cr, Cu, Mn, Ni, Pb and Zn. Transfer factor (TF), daily intake of metals (DIM) and health risk index (HRI) were also calculated. Microbial analysis was carried out for the presence foodborne pathogens. The results showed that the heavy metals contents were higher in the soil than wastewater and the vegetables. Heavy metals ranged (mg•Kg −1) for Cd (1.27 to 2.93), Cr (7.28 to 7.38), Cu (0.91 to 1.70), Mn (0.29 to 6.60), Ni (1.74 to 2.16), Pb (1.32 to 1.69), Zn (3.08 to 3.79); and were higher than the WHO maximum limit permissible (ML) in vegetables. HRI < 1 indicates minimal risk. TF values designated an enhanced bio-contamination. Microbial numeration revealed the presence of spoiler and pathogenic microorganisms. The lettuce tested was not safe for human use, especially for direct consumption by human beings.

REMERCIEMENTS Nous remercions le CRSBAN (UEMOA) et le CIOSPB pour leur appui financier dans la conduite des travaux de recherche. RESUMELa gestion des déchets municipaux est devenue une préoccupation majeure dans les pays en développement, due au manque de politique et de stratégie adaptées. L'étude réalisée a porté sur la valorisation biotechnologique de la fraction biodégradable des déchets au Burkina Faso. Une analyse physico-chimique des déchets échantillonnés dans trois (3) centres de précollecte de déchets municipaux de Ouagadougou a été réalisée. L'influence du type d'inoculum (eaux usées, bouse bovine, flux de broyat de termites et une mixture de ces 3 inocula) et de la charge en substrat (déchets organiques) a été évaluée au cours d'essais de fermentation méthanique. Les résultats obtenus ont montré que les déchets organiques municipaux constituent un substrat de prédilection pour la méthanisation avec un ratio C/N de 31,65. Les essais de fermentation ont permis de noter que la bouse bovine comme inoculum avec une charge en déchets municipaux de 2% donnait la meilleure production de biométhane (297,65 l CH 4 / Kg MSV). Il ressort de cette étude que les déchets municipaux peuvent être traités par la voie de la biométhanisation car présentant un potentiel de bioconversion intéressant. © 2015 International Formulae Group. All rights reserved.Mots clés : Déchets organiques, digestion anaérobie, biométhane, environnement, Burkina Faso. Optimization of biomethane production from municipal solid organic wastes ABSTRACTMunicipal solid organic wastes management became a major preoccupation. The achieved study focuses the biotechnological valorization of the biodegradable fraction of solid organic wastes in Burkina Faso.M. NIKIEMA et al. / Int. J. Biol. Chem. Sci. 9(5): 2743-2756, 2015 2744 Physicochemical characterization analysis of solid wastes sampled in 03 Ouagadougou's centers of municipal wastes deposits was achieved. The influence of inoculum source (wastewater, bovine dung, termites' homogenate and mixture) and substrate concentration (municipal solid waste) were evaluated during biomethane production tests. Results showed that organic fraction of solid wastes represent a source of predilection for methanization with 31.65 C/N cow. Fermentation tests showed that bovine dung used as inoculum in 2% of municipal solid waste gave the highest rate of biomethane production (297.65 l CH 4 / Kg vs). The results demonstrate that municipal wastes can be valorized by biomethanization way because presenting interesting bioconversion potential.

This study is a contribution to the optimization of organic fraction of municipal waste bioconversion into biomethane, by activated sludge production as inoculum for digesters. The wastewater (WW) and cow dung (CD) samples were taken from the slaughterhouse of Ouagadougou town, Burkina Faso. Different mixtures were made, enriched with mineral solution and cellulose at 5% (w/v) as: 10% CD + 90% WW (C7), 30% CD + 70% WW (C6), 50% CD + 50% WW (C5), 70% CD + 30% WW (C4), 90% CD + 10% WW (C3), 100% CD (C2) and 100% WW (C1). The pH evolution and biogas (CH 4 and CO 2) production were followed for 25 days. Cultures tend to acidify with increase in cow dung proportion. Biogas production was significantly higher (p < 0.05) in C5 (880.0 mL), C6 (862.0 10 mL) and C7 (772.0 mL). Mixture C5 had a highest level of CO 2 production (40%). Also C7 and C6 retained in the experiment contained respectively organic matter, volatile fatty acids (VFA) and total alkalinity (TAC) as 41.06%, 47.02%, 1320 mg acetic acid/L, 3036 mg Acetic acid/L and 520 mg CaCO 3 /L, 1310 mg CaCO 3 /L. Mixture C6 was the best medium for microorganism proliferation stability with 3.5 × 10 5 UFC/ml of methanogens bacteria. It also possessed buffering capacity, which prevents acidification of medium during VFAs production.

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