Production of green juice with an intensive thermo-mechanical fractionation process. Part II: Effect of processing conditions on the liquid fraction properties

International audienceThe thermally assisted mechanical dewatering (TAMD) process proved to be efficient to dewater various biomasses. The main idea of this process is to supply heat by conduction through the press walls during the wet fractionation. Applied to spinach leaves, this process led to energy saving but also to a larger amount of green juice. In order to optimize the TAMD process and to evaluate the valorisation potential of the liquid fraction produced, the physico-chemical characteristics of the green juice were investigated. In addition to conventional characterisation methods, an analysis method specific to Rubisco protein (ribulose-1,5-bisphosphate carboxylase/oxygenase) has been developed in the present work. The method enables detection and quantification of Rubisco in green juice samples by using size exclusion chromatographic principles (HPLC SEC). Global methods showed that cut degree of the biomass leaves has an effect on the liquid fraction produced. Indeed, nitrogen content, green and white proteins contents are higher when leaves are finely cut. The investigation of temperature processing effect on juice characteristics by applying the different characterisation methods leads to: - At high temperature (90 degrees C), low nitrogen and fractionated proteins contents in juice, which means that an enriched press cake is produced. - At medium temperature (50 degrees C), higher nitrogen content in juice, which means that a polypeptides-rich liquid I produced. - At low temperature (30 degrees C), HPLC SEC method developed revealed that TAMD process produced a green juice containing biomolecules of high added value such as Rubisco protein

A new biosynthetic tracer for the inline measurement of virus retention in membrane processes: Part II. Biochemical and physicochemical characterizations of the new tracer

International audienc

A new biosynthetic tracer for the inline measurement of virus retention in membrane processes: Part I – Synthesis protocol

International audienc

Characterization of the inline virus removal performances in hollow fibre modules by a new tracer electrochemically detected

International audienceIn a previous work, an innovative and patented method was presented, that is based on a new virus surrogate. This surrogate is an enzyme-labelled MS2 phage that is directly detectable and quantifiable by amperometry thanks to its induced enzymatic activity. In this work, this method was used to characterize the dynamics of virus removal in micromodules as a function of the membrane defect size and the transmembrane pressure (TMP). Experiments were performed at lab scale with an integer module and with modules made with the same fibres with calibrated holes (50, 100, 150 mu m) made in one of the module fibres with the laser method. Results showed first that the new method allowed diagnosing a 50 mu m hole on the fibre of a micromodule. It was also demonstrated that, whatever the applied TMP, removal performances are all the more better that the defect size is smaller. Moreover, whatever the hole size, a TMP step rise from 1 to 1.5 bar during tracer filtration led to no significant change in the observed removal but improved the intrinsic removal performances

Dynamic microbial response under ethanol stress to monitor Saccharomyces cerevisiae activity in different initial physiological states

International audienceDynamic Saccharomyces cerevisiae responses to increasing ethanol stresses were investigated to monitor yeast viability and to optimize bioprocess performance when gradients occurred due to the specific configuration of multi-stage bioreactors with cell recycling or of large volume industrial bioreactors inducing chemical heterogeneities. Twelve fed-batch cultures were carried out with initial ethanol concentrations (Pin) ranging from 5 g l−1 to 110 g l−1 with three different inoculums in different physiological states in terms of viability and quantity of ethanol produced (Po). For a given initial cell viability of 50%, the time to reach the maximum growth rate and maximum ethanol production rate was dependent on the difference Pin − Po. Whatever the initial physiological state, when the initial ethanol concentration Pin reached 100 g l−1, the yeasts died. Experimental results showed that the initial physiological state of the yeast was the major parameter to determine, the microorganisms’ capacities to adapt and resist environmental changes

Improving ethanol production and viability of Saccharomyces cerevisiae by a vitamin feeding strategy during fed-batch process

International audienceSeveral bottlenecks in the alcoholic fermentation process must be overcome to reach a very high and competitive performance of bioethanol production by the yeast Saccharomyces cerevisiae. In this paper, a nutritional strategy is described that allowed S. cerevisiae to produce a final ethanol titre of 19% (v/v) ethanol in 45 h in a fed-batch culture at 30°C. This performance was achieved by implementing exponential feeding of vitamins throughout the fermentation process. In comparison to an initial addition of a vitamin cocktail, an increase in the amount of vitamins and an exponential vitamin feeding strategy improved the final ethanol titre from 126 g l–1 to 135 g l–1 and 147 g l–1, respectively. A maximum instantaneous productivity of 9.5 g l–1 h–1 was reached in the best fermentation. These performances resulted from improvements in growth, the specific ethanol production rate, and the concentration of viable cells in response to the nutritional strategy

Synergistic temperature and ethanol effect on Saccharomyces cerevisiae dynamic behaviour in ethanol bio-fuel production

International audienceThe impact of ethanol and temperature on the dynamic behaviour of Saccharomyces cerevisiae in ethanol biofuel production was studied using an isothermal fed-batch process at five different temperatures. Fermentation parameters and kinetics were quantified. The best performances were found at 30 and 33°C around 120 g l-1 ethanol produced in 30 h with a slight benefit for growth at 30°C and for ethanol production at 33°C. Glycerol formation, enhanced with increasing temperatures, was coupled with growth for all fermentations; whereas, a decoupling phenomenon occurred at 36 and 39°C pointing out a possible role of glycerol in yeast thermal protection

Aeration strategy: a need for very high ethanol performance in Saccharomyces cerevisiae fed-batch process

International audienceIn order to identify an optimal aeration strategy for intensifying bio-fuel ethanol production in fermentation processes where growth and production have to be managed simultaneously, we quantified the effect of aeration conditions—oxygen limited vs non limited culture (micro-aerobic vs aerobic culture)—on the dynamic behaviour of Saccharomyces cerevisiae cultivated in very high ethanol performance fed-batch cultures. Fermentation parameters and kinetics were established within a range of ethanol concentrations (up to 147 g l−1), which very few studies have addressed. Higher ethanol titres (147 vs 131 g l−1 in 45 h) and average productivity (3.3 vs 2.6 g l−1 h−1) were obtained in cultures without oxygen limitation. Compared to micro-aerobic culture, full aeration led to a 23% increase in the viable cell mass as a result of the concomitant increase in growth rate and yield, with lower ethanol inhibition. The second beneficial effect of aeration was better management of by-product production, with production of glycerol, the main by-product, being strongly reduced from 12 to 4 g l−1. We demonstrate that aeration strategy is as much a determining factor as vitamin feeding (Alfenore et al. 2002) in very high ethanol performance (147 g l−1 in 45 h) in order to achieve a highly competitive dynamic process