Abstract This study reports the use of hypotonic osmotic shock as a treatment step to enhance the recoveries of biofuel-convertible lipids and proteins from lipid-rich saltwater Nannochloropsis gaditana (N. gaditana) slurries (biomass content = ~140 mg biomass / g slurry, total lipid content = ~600 mg lipid /g biomass). The osmotic shock was induced through repeated washing of microalgal slurries with multiple batches of fresh water. Subjecting the slurries to 2 stages of freshwater washing resulted in a measurable damage to cell membranes (the uptake of membrane permeability marker increased by 6 folds), a partial loss of cell viability (only 64% of available cells were recoverable), and a minor release of free protein (~2 wt% of available protein) from the biomass into the interstitial space of the slurries. Hypotonic osmotic shock was revealed to be ineffective in rupturing N. gaditana slurries (only 13 ± 9% of available cells were ruptured after 2-stage washing) and, as such, had a limited prospect as a stand-alone cell disruption technology for the saltwater strain. The washing treatment, however, was found to be able to weaken the structural integrity of N. gaditana slurries and enhance the performance of subsequent mechanical or chemical cell disruption technologies when installed as a preparatory step. Applying the washing treatment prior to high-pressure homogenisation (HPH) and low-solvent-to-biomass ratio hexane extraction (hexane : slurry = 1:1 w/w) for the recovery of biofuel-convertible lipids increased the extent of cell rupture from 28 ± 8 to 46 ± 19% of available cells and more than doubled neutral lipid yield from 25.1 ± 2.0 to 64.6 ± 4.9 wt% of available neutral lipid. Initial analysis revealed that the washing treatment had a minimal energy cost (~6% of the total energy expenditure of downstream processing) and that its integration into HPH + hexane lipid recovery led to a 2.5 fold increase in the energy output of the biomass. Partnering the washing treatment with NaOH hydrolysis increased protein yield from 6.7 ± 2.4 to 31.9 ± 10.7 wt% of available protein.

中文翻译：

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低渗渗透休克处理以提高浓缩盐水纳米绿藻浆液中脂质和蛋白质的回收率

摘要 本研究报告了使用低渗渗透休克作为处理步骤，以提高从富含脂质的盐水 Nannochloropsis gaditana (N. gaditana) 浆液（生物质含量 = ~140 mg 生物量/g 浆液，总脂质含量 = ~600 mg 脂质/g 生物量）。渗透休克是通过用多批淡水反复洗涤微藻浆引起的。将浆液进行 2 个阶段的淡水洗涤导致细胞膜受到可测量的损坏（膜渗透性标记物的吸收增加了 6 倍）、细胞活力的部分丧失（只有 64% 的可用细胞可恢复）和轻微的游离蛋白质（可用蛋白质的约 2 重量％）从生物质释放到浆液的间隙空间。低渗渗透休克被证明对破裂 N. gaditana 浆液无效（在 2 阶段洗涤后只有 13 ± 9% 的可用细胞破裂），因此，作为一种独立的细胞破裂技术，其前景有限盐水菌株。然而，发现洗涤处理能够削弱 N. gaditana 浆液的结构完整性，并在作为准备步骤安装时增强后续机械或化学细胞破碎技术的性能。在高压均质 (HPH) 和低溶剂与生物质比己烷提取（己烷：浆液 = 1:1 w/w）之前应用洗涤处理以回收生物燃料可转化脂质增加了细胞破裂的程度从 28 ± 8 到 46 ± 19% 的可用细胞，中性脂质产量从 25.1 ± 2.0 到 64 增加了一倍以上。6 ± 4.9 wt% 的可用中性脂质。初步分析表明，洗涤处理的能源成本最低（占下游加工总能源消耗的 6%），并且将其整合到 HPH + 己烷脂质回收中，使生物质的能量输出增加了 2.5 倍。将洗涤处理与 NaOH 水解相结合将蛋白质产量从可用蛋白质的 6.7 ± 2.4 增加到 31.9 ± 10.7 wt%。