Proteins from Kappaphycus alvarezii: Identification by Mass Spectrometry and Antifungal Potential

K. alvarezii is a red macroalgae cultivated on a large scale in Asian countries. In Brazil, it is cultivated in states such as Piaui, Rio de Janeiro, and São Paulo due to the high economic value for the food industry given the high concentrations of carrageenan, a hydrocolloid formed mainly by carbohydrates, used as a gelling agent and emulsifier. Therefore, to aggregate value to its protein content, the goal was to identify the proteins from K. alvarezii and biotechnological potentials against human pathogens. The protein extract produced Na+-acetate buffer was the most efficient in inhibiting the growth of C. parapsilosis and C. krusei. The analysis of the mechanism of action revealed that proteins from K. alvarezii cause severe damage to cellular morphology, including the effect on the cell wall and membrane, as indicated by scanning electron microscopy (SEM). Fluorescence microscopy agreed with the SEM results, revealing an increase in membrane permeabilization and pore formation, in addition to high levels of ROS, followed by apoptosis triggered by caspase 3/7. Regarding the characterization of proteins, biochemical analysis revealed the presence of proteolytic enzymes and those involved in ROS metabolism. Proteomic analysis by LC-ESI-MS/MS identified 336 proteins involved in processes such as energetic and nucleotide metabolism, defense against (a)biotic stress, and protein folding. Our results revealed that K. alvarezii proteins presented potential against C. parapsilosis and C. krusei.