Abstract
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.
Highlights
Baker’s yeast is currently the most distributed commercial yeast worldwide
The cells were removed by centrifugation and the protein concentration in the supernatant of pulsed cells was determined as described in section “Materials and Methods.”
The data presented in this study demonstrated that the pulsed electric field (PEF) treatment applied in flow mode, followed by incubation of the electropermeabilized yeast cells in a buffer with alkaline pH, resulted in a highly efficient extraction of the intracellular soluble protein with low content of nucleic acid (NA)
Summary
Baker’s yeast is currently the most distributed commercial yeast worldwide. It consists of one or several selected strains of Saccharomyces cerevisiae, which are able to develop very fast and give high biomass quantities. Besides its principal use as a leavening agent in baking and in other traditional fermentation processes, such as wine and beer making, S. cerevisiae which has GRAS (Generally recognized for safe) status has found a variety of applications in agriculture, food, cosmetics, and pharmaceutical industries (Pérez-Torrado et al, 2015; Zymanczyk-Duda et al, 2017). Due to its high content of vitamins, minerals, antioxidants, and other bioactive compounds, the yeast biomass is used in different preparations as health supplements and natural flavor compounds for food industry and as additives for the cosmetic industry (Abbas, 2006)
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