Robust, reliable and controlled bio-methane production

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Enumeration method and medium design for a mixed culture of saccharomyces cerevisiae and chlorella vulgaris

The scientific literature shows a rising interest in studies on symbiotic mixed cultures as an innovative bioprocess to increase biomass and lipid productivity. The main issue with mixed cultures appears to be the dominance of one organism over the other during cultivation. In the current work, a methodology is proposed to develop a co-dominant mixed culture of Saccharomyces cerevisiae GFP and Chlorella vulgaris, in which their growth would be based on mutual symbiosis through recycling O2 and CO2. The first challenge was to develop a rapid and accurate method to distinguish and enumerate each population. Please click on the link below for full content

The circular bioeconomy and the concept of biorefinery

The world is living through a biotechnological and energetic transition phase. The 200-year-old model of a linear economy with its low energy cost and waste producing economy is being challenged by the exhaustion of the planet’s natural resources and by the accumulation of high levels of waste in the environment. Access to clean, renewable energy and fresh water supplies will determine the growth and development of future economies. Globalisation offers a new opportunity for addressing these challenges on a global scale. Please click Additional Files below to see the full abstract

Microalgae culture quality indicators: a review

International audienc

Optimization of a raceway pond system for wastewater treatment: a review

International audienceMicroalgae are photosynthetic microorganisms with potential for biofuel production, CO2 mitigationand wastewater treatment; indeed they have the capacity to assimilate pollutants in wastewaters.Light supply and distribution among the microalgae culture is one of the majorchallenges of photo-bioreactor design, with many studies focusing on microalgae culture systemssuch as raceway ponds (RWP), widely used and cost-effective systems for algal biomass production.This review focuses on possible improvements of the RWP design in order to achieve optimalmicroalgal growth conditions and high biomass productivities, to minimize energyconsumption and to lower the capital costs of the pond. The improvement strategy is based onthree aspects: (1) hydrodynamic characteristics of the raceway pond, (2) evaluation of hydrodynamicand mass transfer capacities of the pond and (3) design of the RWP. Finally, a possibleoptimal design for the RWP is discussed in the context of wastewater treatment

Optimization of a raceway pond system for wastewater treatment: a review

International audienceMicroalgae are photosynthetic microorganisms with potential for biofuel production, CO2 mitigationand wastewater treatment; indeed they have the capacity to assimilate pollutants in wastewaters.Light supply and distribution among the microalgae culture is one of the majorchallenges of photo-bioreactor design, with many studies focusing on microalgae culture systemssuch as raceway ponds (RWP), widely used and cost-effective systems for algal biomass production.This review focuses on possible improvements of the RWP design in order to achieve optimalmicroalgal growth conditions and high biomass productivities, to minimize energyconsumption and to lower the capital costs of the pond. The improvement strategy is based onthree aspects: (1) hydrodynamic characteristics of the raceway pond, (2) evaluation of hydrodynamicand mass transfer capacities of the pond and (3) design of the RWP. Finally, a possibleoptimal design for the RWP is discussed in the context of wastewater treatment

Process for symbiotic culture of Saccharomyces cerevisiae and Chlorella vulgaris for in situ CO2 mitigation

International audienceIndustrial biotechnology relies heavily on fermentation processes that release considerable amounts of CO2. Apart from the fact that this CO2 represents a considerable part of the organic substrate, it has a negative impact on the environment. Microalgae cultures have been suggested as potential means of capturing the CO2 with further applications in high-value compounds production or directly for feed applications. We developed a sustainable process based on a mixed co-dominant culture of Saccharomyces cerevisiae and Chlorella vulgaris where the CO2 production and utilization controlled the microbial ecology of the culture. By mixing yeast and microalga in the same culture, the CO2 is produced in dissolved form and is available to the microalga avoiding degassing and dissolution phenomena. With this process, the CO2 production and utilization rates were balanced and a mutual symbiosis between the yeast and the microalga was set up in the culture. In this study, the reutilization of CO2 and growth of C. vulgaris was demonstrated. The two organism populations were balanced at approximately 20 × 106 cells ml−1 and almost all the CO2 produced by yeast was reutilized by microalga within 168 h of culture. The C. vulgaris inoculum preparation played a key role in establishing co-dominance of the two organisms. Other key factors in establishing symbiosis were the inoculum ratio of the two organisms and the growth medium design. A new method allowed the independent enumeration of each organism in a mixed culture. This study could provide a basis for the development of green processes of low environmental impact

The circular bioeconomy and the concept of biorefinery

International audienc

Effective CO2 capture by the fed-batch culture of Chlorella vulgaris

Microalgae are promising candidates for CO2 capture and concomitant biomass production. Chlorella vulgaris was grown in the batch and fed-batch cultures to develop a culture strategy targeting maximum CO2 capture and conversion to biomass. Growth at five different dissolved CO2 (dCO2) concentrations in the feeding media (atmospheric, 1.55, 1.62, 1.75 and 1.88 g L-1) was tested to assess the effect of dCO2 concentration on the growth, biomass productivity, and nutrients removal efficiency of microalgae. Results suggest that fed-batch culture outperformed "standard" batch cultivation with a higher algal growth rate (2.3 times). As expected, the algal growth was limited at low (atmospheric) dCO2 concentrations and inhibited at high levels (1.75 and 1.88 g L-1). C. vulgaris grown with medium containing 1.62 g L-1 dCO2 showed the highest growth rate (0.094 h-1) with the shortest doubling time (7.4 h), maximum biomass productivity, nitrogen and phosphorus uptake rates (222, 7.5 and 1.6 mg L-1 d-1 , respectively). By pre-dissolving CO2 into the feeding media and using the fed-batch culture mode, a high CO2 removal efficiency could be achieved

Current and novel approaches to downstream processing of microalgae: A review

International audienceBiotechnological application of microalgae cultures at large scale has significant potential in the various fields of biofuels, food and feed, cosmetic, pharmaceutic, environmental remediation and water treatment. Despite this great potential application, industrialisation of microalgae culture and valorisation is still faced with serious remaining challenges in culture scale-up, harvesting and extraction of target molecules. This review presents a general summary of current techniques for harvesting and extraction of biomolecules from microalgae, their relative merits and potential for industrial application. The cell wall composition and its impact on microalgae cell disruption is discussed. Additionally, more recent progress and promising experimental methods and studies are summarised that would allow the reader to further investigate the state of the art. A final survey of energetic assessments of the different techniques is also made. Bead milling and high-pressure homogenisation seem to give clear advantages in terms of target high value compounds extraction from microalgae, with enzyme hydrolysis as a promising emerging technique. Future industrialisation of microalgae for high scale biotechnological processing will require the establishment of universal comparisonstandards that would enable easy assessment of one technique against another