Validation de méthodes performantes d'analyse globale des éléments chimiques (dont la XRF : Spectrométrie de Fluorescence X), appliquées aux terres cultivées et aux intrants valorisables en agriculture

Rapport fina

Ripening influences banana and plantain peels composition and energy content

Musa sp. peels are widely used by smallholders as complementary feeds for cattle in the tropics. A study of the influence of the variety and the maturation stage of the fruit on fermentability and metabolisable energy (ME) content of the peels was performed using banana (Yangambi Km5) and plantain (Big Ebanga) peels at three stages of maturation in an in vitro model of the rumen. Peel samples were analysed for starch, free sugars and fibre composition. Samples were incubated in the presence of rumen fluid. Kinetics of gas production were modelled, ME content was calculated using prediction equation and short-chain fatty acids production and molar ratio were measured after 72 h of fermentation. Final gas production was higher in plantain (269–339 ml g−1) compared to banana (237–328 ml g−1) and plantain exhibited higher ME contents (8.9–9.7 MJ/kg of dry matter, DM) compared to banana (7.7–8.8 MJ/kg of DM). Butyrate molar ratio decreased with maturity of the peels. The main influence of the variety and the stage of maturation on all fermentation parameters as well as ME contents of the peels was correlated to changes in the carbohydrate fraction of the peels, including starch and fibre

Bioconversion of green agricultural herbaceous biomass to ethanol

Biofuels can offer an alternative to fossil fuels in the context of climate change and fossil reserves depletion. Plant biomass consists mainly of structural (cell wall) polysaccharides, but contains also reserve polysaccharides (starch and polyfructans) and soluble sugars, that can be converted by micro-organisms. We examined the feasibility of a simple ethanol fermentation process directly from crude, not sterilized grasses with the commonly used yeast Saccharomyces cerevisae. Crude and steam- and/or polysaccharidase pretreated grass was fermented with S. cerevisiae for 40 hours at 40°C. Ethanol and volatile fatty acids were analyzed by GC-FID. The results show that S. cerevisae can produce ethanol directly from green herbaceous biomass with an ethanol concentration in the range 8–16 g(EthOH)/L without enzyme treatment. Polysaccharidase hydrolysis can increase the ethanol concentration by 20–100%. As crude, not sterilized substrate was used, the endogenous microbial flora was responsible for the production of lactic acid and other volatile fatty acids (mainly acetate and butyrate). The soluble sugar conversion to ethanol was 60–100% of the theorical yield. Enzymatic treatments did not increase significantly the availability of metabolizable sugars for S. cerevisiae. Grass harvest time had also no significant influence on ethanol production. Future work will focus on the characterization of the enzymatic hydrolysis and the release of soluble sugars