Microalgal cell disruption by hydrodynamic cavitation for the production of biofuels

Abstract

Cell disruption is an essential pre-treatment for the efficient extraction of many types of intracellular metabolites such as proteins, carbohydrates, DNAs or lipids; but the high process energy requirement becomes an important issue for low valued commodities such as biofuels. Current mechanical cell disruption methods such as high-pressure homogeniser or sonication require energy input in the order of hundreds of MJ kg −1 of the dry mass; in addition, these methods do not have the capacity suitable for biofuel production where daily processing volumes are in order of mega litres. This study investigated hydrodynamic cavitation (HC) as a cell disruption technique, with levels of disruption determined by i) lipids extracted and ii) the chlorophyll released. It was found that for the lipid extraction, HC has a disruption energy requirement of 3 MJ kg −1 . This amount of energy requirement is more efficient than sonication by a factor of 10; however, it still represents nearly 13 % of the total energy in the biomass and is too high for the production of biofuels. The cell disruption by HC is essentially periplasmic, i.e. mainly confined to the cell wall and membrane. This result suggests that damage to the outer cell barrier such as the cell wall was sufficient to allow for the diffusion of solvents for lipid extraction.

Plant and Biomass Extraction and Valorisation under Hydrodynamic Cavitation

“…The production of renewable energy resources such as biodiesel and biogas via the complex treatment of cyanobacteria biomass is a sustainable strategy. HC-based technologies can increase the efficiency of inedible fat extraction [92], since cell disruption is mainly restrained to the cell wall and membrane [9]. Given its energy efficiency, comparable extractability, and scale-up potential, HC may become an industrial-scale method for microalgae extraction [21].…”

“…As a result, HCR was shown to have 3 MJ/kg of specific energy consumption, indicating that HCR is much more efficient than UAE. Although HC can sufficiently injure the cell wall to leave solvents diffusion for lipid extraction, it still accounts for about 13% of the total biomass energy, which is too high for the biofuels production [9]. Similarly, lipids in microalgae Nannochloropsis sp.…”

“…For the efficient extraction of intracellular metabolites proteins, carbohydrates and lipids, the cell disruption is a crucial procedure [9]. However, the toughness of microalgae cell walls and membranes remediation, food processing, and biofuel production with the advantages of process acceleration and higher energy efficiency [29,30,32].…”

Comparison of Nannochloropsis sp. cells disruption between hydrodynamic cavitation and conventional extraction

“…Hydrodynamic cavitation that was used to cell disruption technique was investigated, with the level of cell disruption was determined by lipids extracted and chlorophyll released. It was found that for lipids extraction, hydrodynamic cavitation technique was requiring energy as big as 3 MJ/kg with the microalgae concentration 1.5-2% w/w [18]. Hydrodynamic cavitation to assist lipid extraction simultaneously from Nannochloropsis Salina sp.…”

Biorefinery of functional biomolecules from algae

“…For cell disintegration, the most common methods include bead milling (chapter 2-5), homogenization (Safi et al, 2014a), high-voltage electric discharges (Zhang et al, 2018), pulsed electric fields and ultrasounds (Grimi et al, 2014;Parniakov et al, 2015), thermal processing and microwaves (Jazrawi et al, 2015;Passos et al, 2015), chemical and enzymatic hydrolysis (Safi et al, 2017a;Sari et al, 2015) and dissolution using ionic liquids (Desai et al, 2016a;Fujita et al, 2013;Teixeira, 2012). Other innovative technologies have been proposed, among which hydrodynamic cavitation (Lee et al, 2015), microfluidization (Cha et al, 2012) and explosive decompression (Lorente et al, 2018;Phong et al, 2018b;Gunerken et al, 2019).…”