Ganeva Valentina, Angelova Boyana, Galutzov Bojidar, Goltsev Vasilij, Zhiponova Miroslava
Biological Faculty, Sofia University "St. Kl. Ohridski", Sofia, Bulgaria.
Front Bioeng Biotechnol. 2020 Dec 15;8:552335. doi: 10.3389/fbioe.2020.552335. eCollection 2020.
Yeasts are rich source of proteins, antioxidants, vitamins, and other bioactive compounds. The main drawback in their utilization as valuable ingredients in functional foods and dietary supplements production is the thick, indigestible cell wall, as well as the high nucleic acid content. In this study, we evaluated the feasibility of pulsed electric field (PEF) treatment as an alternative method for extraction of proteins and other bioactive intracellular compounds from yeasts. Baker's yeast water suspensions with different concentration (12.5-85 g dry cell weight per liter) were treated with monopolar rectangular pulses using a continuous flow system. The PEF energy required to achieve irreversible electropermeabilization was significantly reduced with the increase of the biomass concentration. Upon incubation of the permeabilized cells in water, only relatively small intracellular compounds were released. Release of 90% of the free amino acids and low molecular UV absorbing compounds, 80% of the glutathione, and ∼40% of the total phenol content was achieved about 2 h after pulsation and incubation of the suspensions at room temperature. At these conditions, the macromolecules (proteins and nucleic acids) were retained largely inside. Efficient protein release (∼90% from the total soluble protein) occurred only after dilution and incubation of the permeabilized cells in buffer with pH 8-9. Protein concentrates obtained by ultrafiltration (10 kDa cut off) had lower nucleic acid content (protein/nucleic acid ratio ∼100/4.5) in comparison with cell lysates obtained by mechanical disintegration. The obtained results allowed to conclude that PEF treatment can be used as an efficient alternative approach for production of yeast extracts with different composition, suitable for application in food, cosmetics and pharmaceutical industries.
酵母富含蛋白质、抗氧化剂、维生素和其他生物活性化合物。然而，在将其用作功能性食品和膳食补充剂生产中的宝贵成分时，主要缺点是其细胞壁厚且难以消化，以及核酸含量高。在本研究中，我们评估了脉冲电场（PEF）处理作为从酵母中提取蛋白质和其他生物活性细胞内化合物的替代方法的可行性。使用连续流动系统，对不同浓度（每升12.5 - 85克干细胞重量）的面包酵母水悬浮液进行单极矩形脉冲处理。随着生物质浓度的增加，实现不可逆电通透化所需的PEF能量显著降低。将通透化细胞在水中孵育后，只有相对较小的细胞内化合物被释放出来。在悬浮液于室温下脉动和孵育约2小时后，可释放90%的游离氨基酸和低分子紫外线吸收化合物、80%的谷胱甘肽以及约40%的总酚含量。在这些条件下，大分子（蛋白质和核酸）大部分保留在细胞内。只有在将通透化细胞在pH 8 - 9的缓冲液中稀释和孵育后，才会发生高效的蛋白质释放（约占总可溶性蛋白质的90%）。与通过机械破碎获得的细胞裂解物相比，通过超滤（截留分子量10 kDa）获得的蛋白质浓缩物的核酸含量较低（蛋白质/核酸比约为100/4.5）。所得结果表明，PEF处理可作为一种有效的替代方法，用于生产具有不同组成的酵母提取物，适用于食品、化妆品和制药行业。
