Papachristou I, Akaberi S, Silve A, Navarro-López E, Wüstner R, Leber K, Nazarova N, Müller G, Frey W
Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Bldg 630, 76344, Eggenstein-Leopoldshafen, Germany.
Department of Chemical Engineering, University of Almería, 04120, Almería, Spain.
Biotechnol Biofuels. 2021 Jan 14;14(1):20. doi: 10.1186/s13068-020-01870-1.
Microalgae have attracted considerable interest due to their ability to produce a wide range of valuable compounds. Pulsed Electric Fields (PEF) has been demonstrated to effectively disrupt the microalgae cells and facilitate intracellular extraction. To increase the commercial viability of microalgae, the entire biomass should be exploited with different products extracted and valorized according to the biorefinery scheme. However, demonstrations of multiple component extraction in series are very limited in literature. This study aimed to develop an effective lipid extraction protocol from wet Scenedesmus almeriensis after PEF-treatment with 1.5 MJ·kg. A cascade process, i.e., the valorization of several products in row, was tested with firstly the collection of the released carbohydrates in the water fraction, then protein enzymatic hydrolysis and finally lipid extraction. Biomass processed with high pressure homogenization (HPH) on parallel, served as benchmark.
Lipid extraction with ethanol:hexane (1:0.41 vol/vol) offered the highest yields from the different protocols tested. PEF-treatment promoted extraction with almost 70% of total lipids extracted against 43% from untreated biomass. An incubation step after PEF-treatment, further improved the yields, up to 83% of total lipids. Increasing the solvent volume by factor 2 offered no improvement. In comparison, extraction with two other systems utilizing only ethanol at room temperature or elevated at 60 °C were ineffective with less than 30% of total lipids extracted. Regarding cascade extraction, carbohydrate release after PEF was detected albeit in low concentrations. PEF-treated samples displayed slightly better kinetics during the enzymatic protein hydrolysis compared to untreated or HPH-treated biomass. The yields from a subsequent lipid extraction were not affected after PEF but were significantly increased for untreated samples (66% of total lipids), while HPH displayed the lowest yields (~ 49% of total lipids).
PEF-treatment successfully promoted lipid extraction from S. almeriensis but only in combination with a polar:neutral co-solvent (ethanol:hexane). After enzymatic protein hydrolysis in cascade processing; however, untreated biomass displayed equal lipid yields due to the disruptive effect of the proteolytic enzymes. Therefore, the positive impact of PEF in this scheme is limited on the improved reaction kinetics exhibited during the enzymatic hydrolysis step.
微藻因其能够产生多种有价值的化合物而备受关注。脉冲电场（PEF）已被证明能有效破坏微藻细胞并促进细胞内物质的提取。为提高微藻的商业可行性，应根据生物精炼方案对整个生物质进行开发，提取并增值不同的产品。然而，文献中关于串联多组分提取的实例非常有限。本研究旨在开发一种有效的脂质提取方案，用于对经1.5 MJ·kg的PEF处理后的湿生阿尔梅里亚栅藻进行脂质提取。测试了一种级联工艺，即依次对几种产品进行增值处理，首先收集水相中释放的碳水化合物，然后进行蛋白质酶解，最后进行脂质提取。同时对平行采用高压均质化（HPH）处理的生物质进行了测试，作为基准。
在测试的不同方案中，用乙醇:己烷（1:0.41体积/体积）进行脂质提取的产率最高。PEF处理促进了脂质提取，总脂质提取率达到近70%，而未处理生物质的提取率为43%。PEF处理后的孵育步骤进一步提高了产率，总脂质提取率高达83%。将溶剂量增加两倍并没有提高提取效果。相比之下，另外两种仅在室温或60℃下使用乙醇的提取系统效果不佳，总脂质提取率低于30%。关于级联提取，尽管PEF处理后检测到碳水化合物释放，但浓度较低。与未处理或HPH处理的生物质相比，PEF处理的样品在酶促蛋白质水解过程中表现出稍好的动力学。PEF处理后后续脂质提取的产率没有受到影响，但未处理样品的产率显著提高（总脂质的66%），而HPH处理的产率最低（约为总脂质的49%）。
PEF处理成功促进了阿尔梅里亚栅藻脂质的提取，但仅在与极性:中性共溶剂（乙醇:己烷）结合使用时有效。在级联处理中的酶促蛋白质水解后，由于蛋白水解酶的破坏作用，未处理的生物质显示出相同的脂质产率因此，在该方案中，PEF对酶解步骤中表现出的反应动力学改善的积极影响有限。
