Biodiversity as a tool for waste phycoremediation and biomass production

International audienc

Complementary support for the new ecological concept of ‘bacterial independence on contemporary phytoplankton production’ in oceanic waters

International audienc

About frame estimation of growth functions and robust prediction in bioprocess modeling

We address the problem of determining functional framing from experimental data points in view of robust time-varying predictions, which is of crucial importance in bioprocess monitoring. We propose a method that provides guaranteed functional bounds, instead of sets of parameters values for growth functions such as the classical Monod or Haldane functions commonly used in bioprocess modeling. We illustrate the applicability of the method with bioreactor simulations in batch and continuous mode, as well as on real data. We also present two extensions of the method adding flexibility in its application, and discuss its efficiency in providing guaranteed state estimations

Growth of Chlorella sorokiniana on a mixture of volatile fatty acids: The effects of light and temperature

International audienceThis study investigated the influence of light and temperature on Chlorella sorokiniana grown on a mixture of acetate and butyrate, two of the volatile fatty acids produced by dark fermentation. Exposure to light caused autotrophic biomass production (56% of the final biomass) and reduced the time to reach butyrate exhaustion to 7 days at 25°C from 10 days in the dark. For growth on acetate at the optimum temperature (35°C), the presence of butyrate reduced the growth rate (by 46%) and the carbon yield (by 36%). For successful microalgae growth on dark fermentation effluent, butyrate inhibition may be reduced by setting the temperature to 30°C and providing light

Demonstration of facilitation between microalgae to face environmental stress

International audiencePositive interactions such as facilitation play an important role during the biological colonization and species succession in harsh or changing environments. However, the direct evidence of such ecological interaction in microbial communities remains rare. Using common freshwater microalgae isolated from a High Rate Algal Pond HRAP treating wastewaters, we investigated with both experimental and modeling approaches the direct facilitation between two algal strains during the colonization phase. Our results demonstrate that the first colonization by microalgae under a severe chemical condition arose from the rapid growth of pioneer species such as Chlorella sorokiniana, which facilitated the subsequent colonization of low growth specialists such as Scenedesmus pectinatus. The pioneer species rapidly depleted the total available ammonia nitrogen favoring the specialist species initially inhibited by free ammonia toxicity. This latter species ultimately dominated the algal community through competitive exclusion under low nutrient conditions. We show that microbial successions are not only regulated by climatic conditions but also by interactions between species based on the ability to modify their growth conditions. We suggest that facilitation within the aquatic microbial communities is a widespread ecological interaction under a vast range of environmental stress

Demonstration of facilitation between microalgae to face environmental stress

Positive interactions such as facilitation play an important role during the biological colonization and species succession in harsh or changing environments. However, the direct evidence of such ecological interaction in microbial communities remains rare. Using common freshwater microalgae isolated from a High Rate Algal Pond HRAP treating wastewaters, we investigated with both experimental and modeling approaches the direct facilitation between two algal strains during the colonization phase. Our results demonstrate that the first colonization by microalgae under a severe chemical condition arose from the rapid growth of pioneer species such as Chlorella sorokiniana, which facilitated the subsequent colonization of low growth specialists such as Scenedesmus pectinatus. The pioneer species rapidly depleted the total available ammonia nitrogen favoring the specialist species initially inhibited by free ammonia toxicity. This latter species ultimately dominated the algal community through competitive exclusion under low nutrient conditions. We show that microbial successions are not only regulated by climatic conditions but also by interactions between species based on the ability to modify their growth conditions. We suggest that facilitation within the aquatic microbial communities is a widespread ecological interaction under a vast range of environmental stress

Facilitation écologique entre deux espèces de microalgues <em> Chlorella sorokiniana</em> & <em>Scenedesmus acutus</em>

National audienceUne facilitation écologique entre deux espèces de microalgues Chlorella sorokiniana et Scenedesmus acutus, classiquement observées dans les eaux fortement anthropisées, riches en ammonium (NH4+), est démontrée. En effet, des expérimentations en laboratoire ont montré que la croissance de Scenedesmus acutus est inhibée pour les très fortes valeurs d'ammonium (NH4+), à cause de la toxicité en ammoniaque (NH3), ce qui n'est pas le cas pour Chlorella sorokiniana. Cette dernière espèce possède toutefois une affinité pour le (NH4+), plus faible que Scenedesmus acutus. Une modélisation mathématique a été réalisée à partir de ces résultats expérimentaux et a permis de démontrer la succession écologique de ces espèces lorsqu'elles sont présentes ensemble. Ainsi lors d'apports très riches en NH4+, la croissance rapide de C. sorokiniana colonise en premier le milieu, réduisant la teneur en NH4+ (et donc en NH3 permettant à S. acutus de croître (facilitation) et même de gagner la compétition pour ce nutriment