Pascal Jaouen

Stabilized landfill leachate treatment by combined physicochemical-nanofiltration processes

Landfill leachate is a complex wastewater which the composition and concentration of contaminants are influenced by the type of waste deposited and the age of landfill. In the last years, several processes or process combinations were developed and tested to reach requirements for the discharge of leachate. Among the new processes, membrane processes are considered as promising: reverse osmosis is one of the most widely used treatment in the Northwestern European countries and nanofiltration is gained in popularity during the last 5 years. Successful application of membrane technology for the treatment of landfill leachates, requires efficient control of membrane fouling. Two organic membranes of nanofiltration were used for pilot-scale testing. Leachates were subject to several pretreatments (pH modification, prefiltration and coagulation with FeCl3) to remove potential foulants including dissolved organic and inorganic substances, colloidal and suspended particles. These pretreatments do not enhance the performances (retention and permeation flux) of membranes because the pH range and the presence of Fe3+ ions contribute greatly to change the characteristics of organic matter and the surface charges of membranes. However, the results show that nanofiltration is sufficient to eliminate refractory COD, the permeates have a COD lower than the requirements for discharge.

Enzymatic hydrolysis of cuttlefish (Sepia officinalis) and sardine (Sardina pilchardus) viscera using commercial proteases: effects on lipid distribution and amino acid composition.

Total lipid and phospholipid recovery as well as amino acid quality and composition from cuttlefish (Sepia officinalis) and sardine (Sardina pilchardus) were compared. Enzymatic hydrolyses were performed using the three proteases Protamex, Alcalase, and Flavourzyme by the pH-stat method (24 h, pH 8, 50 degrees C). Three fractions were generated: an insoluble sludge, a soluble aqueous phase, and an oily phase. For each fraction, lipids, phospholipids, and proteins were quantified. Quantitative and qualitative analyses of the raw material and hydrolysates were performed. The degree of hydrolysis (DH) for cuttlefish viscera was 3.2% using Protamex, 6.8% using Flavourzyme, and 7% using Alcalase. DH for sardine viscera was 1.9% (using Flavourzyme), 3.1% (using Protamex) and 3.3% (using Alcalase). Dry matter yields of all hydrolysis reactions increased in the aqueous phases. Protein recovery following hydrolysis ranged from 57.2% to 64.3% for cuttlefish and 57.4% to 61.2% for sardine. Tissue disruption following protease treatment increased lipid extractability, leading to higher total lipid content after hydrolysis. At least 80% of the lipids quantified in the raw material were distributed in the liquid phases for both substrates. The hydrolysed lipids were richer in phospholipids than in the lipids extracted by classical chemical extraction, especially after Flavourzyme hydrolysis for cuttlefish and Alcalase hydrolysis for sardine. The total amino acid content differed according to the substrate and the enzyme used. However, regardless of the raw material or the protease used, hydrolysis increased the level of essential amino acids in the hydrolysates, thereby increasing their potential nutritional value for feed products.

The shear stress of microalgal cell suspensions (Tetraselmis suecica) in tangential flow filtration systems: the role of pumps

A widely used technique for cell harvesting is crossflow microfiltration. The relative fragility of microalgae requires choosing a suitable pumping system. Tetraselmis suecica, which is a very mobile alga, is an interesting model for this study. The extent of damage observed in various pumps was measured as a function of the number of passes of the algal suspension through the pumps in a closed loop. A loss of microalgal motility could occur with either centrifugal or rotary vane positive displacement pumps. On the contrary, electronic microscope observation revealed that, during concentration using an eccentric rotor pump or a peristaltic pump, microalgae were not damaged.

Impact of ultrafiltration and nanofiltration of an industrial fish protein hydrolysate on its bioactive properties

BACKGROUND Numerous studies have demonstrated that in vitro controlled enzymatic hydrolysis of fish and shellfish proteins leads to bioactive peptides. Ultrafiltration (UF) and/or nanofiltration (NF) can be used to refine hydrolysates and also to fractionate them in order to obtain a peptide population enriched in selected sizes. This study was designed to highlight the impact of controlled UF and NF on the stability of biological activities of an industrial fish protein hydrolysate (FPH) and to understand whether fractionation could improve its content in bioactive peptides. RESULTS The starting fish protein hydrolysate exhibited a balanced amino acid composition, a reproducible molecular weight (MW) profile, and a low sodium chloride content, allowing the study of its biological activity. Successive fractionation on UF and NF membranes allowed concentration of peptides of selected sizes, without, however, carrying out sharp separations, some MW classes being found in several fractions. Peptides containing Pro, Hyp, Asp and Glu were concentrated in the UF and NF retentates compared to the unfractionated hydrolysate and UF permeate, respectively. Gastrin/cholecystokinin-like peptides were present in the starting FPH, UF and NF fractions, but fractionation did not increase their concentration. In contrast, quantification of calcitonin gene-related peptide (CGRP)-like peptides demonstrated an increase in CGRP-like activities in the UF permeate, relative to the starting FPH. The starting hydrolysate also showed a potent antioxidant and radical scavenging activity, and a moderate angiotensin-converting enzyme (ACE)-1 inhibitory activity, which were not increased by UF and NF fractionation. CONCLUSION Fractionation of an FPH using membrane separation, with a molecular weight cut-off adapted to the peptide composition, may provide an effective means to concentrate CGRP-like peptides and peptides enriched in selected amino acids. The peptide size distribution observed after UF and NF fractionation demonstrates that it is misleading to characterize the fractions obtained by membrane filtration according to the MW cut-off of the membrane only, as is currently done in the literature.

Recovery by nanofiltration and reverse osmosis of marine flavours from seafood cooking waters

Abstract Cooking waters from buckies, shrimps and tuna have a high level of polluting load (Chemical Oxygen Demand — COD — comprised between 5 and 40 gO2/L) and have to be treated before being rejected in the environment. However, these juices seem to contain interesting flavour compounds. This recovery would allow the industrialists to diminish the waste water treatment cost and to recover high added value molecules. In this work, a membrane process system consisting in ultrafiltration (UF) followed by uanofiltration (NF) or reverse osmosis (RO) was used to reduce the pollution load and to concentrate flavour compounds of seafood cooking juices (buckies, shrimps and tuna). The first ultrafiltration step (cut-off: 0.02 μm) consisted in clarifying the cooking waters in order to increase fluxes of the following filtrations. NF (cut-off: 300 Da) did not seem to be efficient enough for flavour recovery, whereas RO was, for shrimps and buckies cooking juices. At the opposite, aromas contained in the tuna cooking juice were not perfectly retained by the RO membrane used. Nevertheless, the polluting load was considerably decreased after RO (COD reduced by 95% for shrimps and buckies and 85% for tuna).

Arthrospira platensis harvesting with membranes: fouling phenomenon with limiting and critical flux.

The present work deals with the harvesting of Arthrospira platensis (Spirulina) from a diluted culture medium. This cyanobacterium was retained by the European Space Agency as food supply for long term manned spatial missions, and integrated in the MELiSSA project: an artificial microecosystem which supports life in space. Membranes techniques seem to be adapted to efficiency, reliability and safety constraints, even if a well-known limitation is the progressive fouling and permeation flux decrease. Among usual solid/liquid separation processes, Arthrospira harvesting is performed by tangential ultrafiltration (tubular inorganic membrane 50 kD Céram-Inside from Tami, Nyons, France). To ensure a reliable separation step with the best biomass quality, a good comprehension of the ultrafiltration progress and fouling phenomenon is needed, in particular, the link between operating parameters, permeation flux and cleanability. Comparative experiments were made between limiting and critical flux with different suspensions: fresh biomass, stressed biomass and a suspension of Arthrospira platensis enriched with exopolysaccharides.

Physicochemical factors affecting the stability of two pigments: R-phycoerythrin of Grateloupia turuturu and B-phycoerythrin of Porphyridium cruentum.

Phycoerythrin is a major light-harvesting pigment of red algae, which could be used as a natural dye in foods. The stability of R-phycoerythrin of Grateloupia turuturu and B-phycoerythrin of Porphyridium cruentum in relation to different light exposure times, pHs, and temperatures was studied. Regarding the light exposure time, after 48h, the reduction in concentrations of B-phycoerythrin and R-phycoerythrin were 30±2.4% and 70±1%, respectively. Phycoerythrins presented good stability from pH 4 to 10. At pH 2, the reduction in concentration was 90±4% for B-phycoerythrin and 40±2.5% for R-phycoerythrin while, at pH 12, the phycoerythrins were degraded. Phycoerythrins showed good stability toward temperature, up to 40°C. At 60°C, the reduction in concentrations of B-phycoerythrin and R-phycoerythrin were 50±3.4% and 70±0.18%, respectively. Moreover, the best conditions of storage (-20°C) were determined.

The culture of Chlorella vulgaris in a recycled supernatant: Effects on biomass production and medium quality

Reusing supernatant of microalgae culture medium can have inhibitory or toxic effects on the biomass production because of the release of organic metabolites by cells in the culture medium during their growth. This work investigated the impact of Chlorella vulgaris medium recycling on culture productivity, cells quality and accumulation of excreted metabolites in the culture medium. No significant impact on the C. vulgaris growth was observed after 63days of recycling, the productivity remained stable at around 0.55kgm(-3)day(-1). Organic matters accumulated in supernatant were identified as biopolymers (BP) poor in nitrogen and with a size above 40kDa (probably polysaccharides), and small organic molecules (SOM) richer in nitrogen with a molecular size ranging from 1 to 3kDa. The concentration of biopolymers in the supernatant increased till to a maximum and then decreased, possibly consumed by bacteria, whereas small organic compounds accumulated in the medium.

Development and validation of a minimal growth medium for recycling Chlorella vulgaris culture.

When microalgae culture medium is recycled, ions (e.g. Na(+), K(+), Ca(2+)) that were not assimilated by the microalgae accumulate in the medium. Therefore, a growth medium (HAMGM) was developed that included ions that were more easily assimilated by Chlorella vulgaris, such as ammonium one (NH(4)(+)). Recycling performance was studied by carrying out 8-week continuous cultivation of C. vulgaris with recycled HAMGM medium. No loss of biomass productivity was observed compared to culture in a conventional medium, and accumulation of ions over time was negligible.

Determination of cake thickness and porosity during cross-flow ultrafiltration on a plane ceramic membrane surface using an electrochemical method

The thickness and the porosity of a deposit during ultrafiltration experiments are determined using an electrochemical method. Twenty microelectrodes are mounted flush to a ceramic plane membrane and maps of deposit thickness are determined for three inlet/outlet distributors configurations. Combining an electrochemical method and a step transient method, the determination of the thickness and the porosity of a particles deposit is performed. These local thickness and porosity values are analyzed thanks to wall shear stress local measurements obtained in a previous work [Sep. Sci. Technol. 37 (10) (2002) 2251]. The results emphasize the heterogeneity of the deposit thickness, especially in zones of low wall shear stress. Furthermore, the porosity values of the deposit are ranged between 0.3 and 0.8 as a function of the location at the membrane surface.