An effective, cost-efficient extraction method of biomass from wet microalgae with a functional polymeric membrane

Abstract

For energy-efficient extraction of biomass from microalgae, it is essential to extract the intracellular lipid directly from wet microalgae without drying the microalgal biomass. In this work, a novel, highly efficient cell disruption process was devised using a functional membrane coated with a cationic polymer. The proposed mechanism of cell disruption involves the perturbation of the local electrostatic equilibrium of the amphiphilic microalgal cell membrane caused by the direct contact with the tertiary-amine cations on the surface of the membrane. A tert-amine-containing polymer, poly-dimethylaminomethylstyrene ( pDMAMS) film was conformally deposited on a nylon membrane by a vapor-phase polymerization process, termed as initiated chemical vapor deposition (iCVD). For the wet extraction with this membrane, the pDMAMS-coated membrane was immersed in a microalgal culture of Aurantiochytrium sp. KRS101.The microalgal culture was simply shaken together with the membrane to prompt the contact with the pDMAMS-coated membrane. With this ultimately simple procedure, the bursting of cells was clearly observed. Surprisingly, by this simple, energy-efficient process, a significantly high disruption yield of 25.6 ± 2.18% was achieved. The membrane-based extraction process is highly desirable in that (1) the process does not require an energy-consuming drying procedure, and (2) the proposed cell disruption method with a functional membrane is extremely simple and highly efficient. † Electronic supplementary information (ESI) available. See

Cell disruption technologies

“…To solve the problem of enzyme cost, both microbes excreting enzymes or immobilizing enzymes can be used. However, information about these two approaches is scarce (Yoo et al, 2014).…”

“…Hydrothermal pretreatments have exposure times of 5-30 min, temperatures above 100°C, and elevated pressures (<220 bars) in an autoclave. During steam explosion, biomass remains under saturated vapor pressure at high temperature (140-180°C) and pressure for a variable time (from 5 to 60 min) (Yoo et al, 2014). The entire mixture of microalgae and steam is subsequently flashed, and the biomass is cooled down in another vessel.…”

“…The quality of products released by ionic liquids and supercritical fluids is high compared to conventional pretreatments due to its self-separation and recyclability. However, the high prize of ionic liquids increases the process costs (Yoo et al, 2014). Moreover, Zhou et al (2012) reported inhibitor compounds (furfural and 5-hydroximethylfurfural) in their work with ionic liquids since temperatures above 120°C caused carbohydrate degradation.…”

“…Chemicals may influence the quality of the products due to the formation of by-products like inhibitors (e.g., furfural and 5-hydroxymethylfurfural). Moreover, a pretreatment applied to release one fraction can solubilize and degrade other biomass components, affecting the biorefinery concept (Yoo et al, 2014). Enzymes achieve high product quality but still remain expensive.…”

“…Another technique that focuses energy is high-frequency (3.2 MHz) focused ultrasonication, which proved to consume less energy than conventional ultrasonication (20 kHz), but efficient rupture would require the combination of both techniques (Wang et al, 2014). Yoo et al (2014) describe an immobilized chemical disruption method in which a surfactant immobilized on a membrane is used as a disruption agent. Cell disruption efficiency, however, was not so high (25.6%).…”