Energy consumption and water-soluble protein release by cell wall disruption of Nannochloropsis gaditana

Abstract

Several cell disruption methods were tested on Nannochloropsis gaditana, to evaluate their efficiency in terms of cell disintegration, energy input and release of soluble proteins. High-pressure homogenization (HPH) and bead milling were the most efficient with >95% cell disintegration, ±50% (w/w) release of total proteins and low energy input (<0.5kWh.kg). Enzymatic treatment required low energy input (<0.34kWh.kg), but it only released ±35% protein (w/w). Pulsed Electric Field (PEF) was neither energy-efficient (10.44kWh.kg) nor successful for protein release (only 10% proteins w/w) and cell disintegration. The release of proteins after applying HPH and bead milling always required less intensive operating conditions for cell disruption. The energy cost per unit of released protein ranged from 0.15-0.25 €.kg in case of HPH, and up to 2-20 €.kg in case of PEF.

Main Variables Affecting a Chemical-Enzymatic Method to Obtain Protein and Amino Acids from Resistant Microalgae

“…Furthermore, low-cost applications of microalgae require the use of fresh biomass to avoid the previous costly drying even though microorganisms preserve their cell wall intact, which hinder the bioproducts recovering. Disruption techniques such as bead milling and high-pressure homogenization have demonstrated to be very effective and relatively energy-efficient methods [12,13] though they require specific equipment for which inversion costs are only feasible for some applications [8][9][10]. In contrast, from an operational point of view, alkaline and/or enzymatic methods could be characterized by their simplicity and therefore applicable to low-cost uses.…”

Biorefinery of functional biomolecules from algae

“…In the present study we measured a protein yield of 22.5 % and an E m of 0.607 ± 0.002 kWh kg DW -1 . Safi et al, (2017a) reported yields from 23 to 51 % and corresponding energy consumptions of 0.1 to 0.6 kWh kg DW -1 for the microalgae Nannochloropsis gaditana using bead milling and high pressure homogenization. Such high yields reflect structural differences between the two algae strains, since both works implemented comparable operation conditions for the case of the bead milling (BM) process.…”

“…2C, all the protein bands expected for T. suecica (Postma et al, 2016) are preserved, confirming the mildness of the present extraction process. (Postma et al, 2016;Postma et al, 2015;Safi et al, 2017a)), EF: Electric Fields ('t Grimi et al, 2014;Parniakov et al, 2015;Postma et al, 2016;Safi et al, 2017a), US: Sonication (Grimi et al, 2014;Parniakov et al, 2015;Passos et al, 2015;Safi et al, 2014c;Wenjuan et al, 2013), HPH: High Pressure Homogenization (Grimi et al, 2014;Safi et al, 2017aSafi et al, , 2014aSafi et al, , 2014c, MW: Microwaves (Passos et al, 2015), Thermal processing (Jazrawi et al, 2015;Passos et al, 2015), Em min : Minimum specific energy for cell rupture (Günther et al, 2016;Lee et al, 2013), Em Ext : Target maximum specific energy for extraction (Coons et al, 2014;Illman et al, 2000).…”

“…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).…”

“…However, these are still orders of magnitudes higher than the energy required to break the cells (1.9x10 -4 -2.5x10 -3 kWh kg DW -1 ) (Günther et al, 2016;Lee et al, 2013). methods usually lead to high disintegration and extraction yields and lower energy consumptions (0.3 kWh kg DW -1 , (Safi et al, 2017a;Sari et al, 2013)). However, the costs associated with the enzymes and chemicals are still prohibitive (Sari et al, 2015).…”