Cross-flow filtration for the recovery of lipids from microalgae aqueous extracts: Membrane selection and performances

Abstract

The biorefinery of microalgae necessitates innovative choices of soft and energy-efficient processes to guarantee the integrity of fragile molecules and develop eco-friendly production. A wet processing of biomass is proposed, which avoids expensive drying steps. It includes harvesting, cell disruption, and fractionation of the target compounds. Membrane filtration is a promising clean fractionation step. In this paper, the recovery of lipids from starving Parachlorella kessleri aqueous extracts by cross-flow filtration was studied. A model solution was formulated to test four membranes of different materials (PVDF, PES, PAN) and cutoffs (200 kDa-1.5 µm). The hydrophilic PAN 500 kDa membrane presented the best performance (flux stability, permeate flux, lipid retention, and cleanability) and was therfore selected for filtrating real aqueous extracts. Similar permeation fluxes were obtained with model and real products: 34-41 L h −1 m −2 respectively. The coalescence of lipid droplets was observed with model solutions but not with real products, less concentrated. The lipids from the real products were wholly retained by the PAN membrane, whereas some of the polysaccharides and proteins were able to permeate. An optimization of the coupling between culture, cell disruption, clarification, and filtration would allow a good concentration and purification of the lipids from microalgae.

Membrane-Based Harvesting Processes for Microalgae and Their Valuable-Related Molecules: A Review

“…However, too small membrane cut-offs may be more conducive to adsorption pore blocking or cake formation. Hydrophobic membranes may also promote fouling during the filtration of microalgae extracts with a high lipids content [ 110 , 111 ]. Lipid recovery efficiency varies in a wide range from 3 up to 98% depending mainly on the extraction process (e.g., reverse osmosis, dynamic filtration and cross-flow filtration), type and characteristics of the membrane used (e.g., polyimide, polysulfone and polyacrylonitrile) and operating conditions [ 112 ].…”

Effects of Flocculant Concentration and Temperature on the Membrane Separation Process in Microalgal Suspensions

“…The filtration efficiency was greater than 99 % for all membranes. Rivera et al studied the use of crossflow filtration to extract lipid from Parachlorella kessleri microalgae after the milling and centrifugation processes rather than to harvest the microalgal culture [28]. The four membranes used were made of polyethersulfone, PAN, and two polyvinylidene fluorides.…”

Harvesting Microalgae for Food and Energy Products

“…[ 58 ] While smaller pore sizes limit flux (rate of filtration) with pure water, the reduced fouling may justify the use of UF membranes. [ 59–61 ] Fouling may depend on system flow, whereby alternating the direction of flow into the filter [ 62 ] or using cross‐flow systems with higher bulk flow velocity [ 63 ] improve filtration performance by reducing fouling. Sand or other coarse materials have been used to avoid fouling of the membrane, with improvements in cost effectiveness.…”

“…[ 64 ] Membrane composition is important, as it can lead to substantial differences in flux for a given pore size with pure water, [ 59 ] and can induce fouling by the adsorption of polysaccharides or other macromolecules on hydrophobic membranes. [ 60,61 ] Negatively charged surface coatings can similarly improve resistance to fouling. [ 65 ] Negatively charged membrane surfaces can alternately be created by applying current to conductive ceramic filters, with comparable benefits to fouling resistance.…”