Carullo Daniele, Pataro Gianpiero, Donsì Francesco, Ferrari Giovanna
Department of Industrial Engineering, University of Salerno, Fisciano, Italy.
ProdAl Scarl - University of Salerno, Fisciano, Italy.
Front Bioeng Biotechnol. 2020 Sep 4;8:551272. doi: 10.3389/fbioe.2020.551272. eCollection 2020.
The present study aimed to investigate the effect of the main pulsed electric field (PEF) process parameters on the cell damages of microalgae and the extractability of valuable compounds [water-soluble proteins (WSP), C-phycocyanin (C-PC), and carbohydrates (CH)]. Aqueous microalgae suspensions (2%, w/w) were PEF-treated at variable field strength ( = 10, 20, 30 kV/cm), total specific energy ( = 20, 60, 100 kJ/kg), and inlet temperature (25, 35, 45°C), with either monopolar or bipolar square wave pulses (5 μs of width, delay time between pulses of opposite polarities = 1, 5, 10, 20 μs), prior to extraction with water at room temperature (25°C) for up to 3 h. High-pressure homogenization (HPH) treatment ( = 150 MPa, 3 passes) was used to achieve complete cell disruption to quantify the total extractable content of target intracellular compounds. Scanning electron microscopy (SEM) and optical microscopy analyses clearly showed that PEF merely electroporated the membranes of algae cell, without damaging the cell structure and forming cell debris. The application of PEF treatment (monopolar pulses, 20 kV/cm and 100 kJ/kg) at room temperature significantly enhanced the extraction yield of WSP [17.4% dry weight (DW)], CH (10.1% DW), and C-PC (2.1% DW), in comparison with the untreated samples. Bipolar pulses appeared less effective than monopolar pulses and led to extraction yields dependent on the delay time. Additionally, regardless of pulse polarity, a clear synergistic effect of the combined PEF (20 kV/cm and 100 kJ/kg)-temperature (35°C) treatment was detected, which enabled the extraction of up to 37.4% (w/w) of total WSP, 73.8% of total CH, and 73.7% of total C-PC. Remarkably, the PEF treatment enabled to obtain C-phycocyanin extract with higher purity than that obtained using HPH treatment. The results obtained in this work suggest that the application of PEF combined with mild heating could represent a suitable approach for the efficient recovery of water-soluble compounds microalgal biomass.
本研究旨在探究主要脉冲电场（PEF）工艺参数对微藻细胞损伤以及对有价值化合物[水溶性蛋白质（WSP）、C-藻蓝蛋白（C-PC）和碳水化合物（CH）]提取率的影响。将微藻水悬浮液（2%，w/w）在可变场强（ = 10、20、30 kV/cm）、总比能（ = 20、60、100 kJ/kg）和入口温度（25、35、45°C）条件下进行PEF处理，采用单极或双极方波脉冲（宽度5 μs，相反极性脉冲之间的延迟时间 = 1、5、10、20 μs），然后在室温（25°C）下用水提取长达3小时。使用高压均质（HPH）处理（ = 150 MPa，3次）实现细胞完全破碎，以量化目标细胞内化合物的总可提取含量。扫描电子显微镜（SEM）和光学显微镜分析清楚地表明，PEF仅使藻细胞膜发生电穿孔，而未破坏细胞结构和形成细胞碎片。与未处理样品相比，在室温下应用PEF处理（单极脉冲，20 kV/cm和100 kJ/kg）显著提高了WSP[干重（DW）的17.4%]、CH（DW的10.1%）和C-PC（DW的2.1%）的提取率。双极脉冲似乎比单极脉冲效果差，且提取率取决于延迟时间。此外，无论脉冲极性如何，均检测到PEF（20 kV/cm和100 kJ/kg）与温度（35°C）联合处理具有明显的协同效应，这使得总WSP的提取率高达37.4%（w/w）、总CH的提取率高达73.8%以及总C-PC的提取率高达73.7%。值得注意的是，PEF处理能够获得比使用HPH处理更高纯度的C-藻蓝蛋白提取物。本研究所得结果表明，PEF与温和加热相结合的应用可能是一种从微藻生物质中高效回收水溶性化合物的合适方法。
