Disintegration of dried yeast cells andist effect on protein extractability, sedimentation property and viscosity of the cell suspension

Author(s): Lee C, Tsang SK, Urakabe R, Rha CK

Abstract

The morphology of dried Candida lipolytica yeast suspended in aqueous solutions (H2O, 0.4% NaOH, 2N HCl, and 6N HCl) and organic solvents (95% alcohol and acetone) was studied using a scanning electron microscope (SEM) and an optical microscope. The effect of high-pressure homogenization on cell-wall structure and cell clumps was also determined. The protein extractability, sedimentation property, and viscosity of cells subjected to different mechanical and chemical treatments were also investigaged. The dried yeast cells were in a spherical agglomeration consisting of 100s of closely bound cells. The clump was resistant to water, aqueous 2N HCl solution at 25°C, 95% alcohol and acetone, but vulnerable to 6N HCl, aqueous 0.4% NaOH solution, and homogenization. The homogenization of the cell suspension not only broke the clump but also cracked the cell-wall structure. The aqueous alkaline solution could have weakened the cell wall and increased the solubility of the protein released through the cracks in the cell wall. The destruction of the agglomeration and the cell-wall structure increased the hydration of the cell and thereby increased the stability of the suspension. The sedimentation and the viscosity of the cell suspension corresponded to the morphological changes and the extractability of protein in the cell suspensions with different treatments.

 

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