Antifungal activity of α-helical propeptide SnuCalCpI15 derived from Calotropis procera R. Br. against food spoilage yeasts

Abstract

Food spoilage caused by yeast is a common problem in the food industry, and has led to the use of chemical preservatives. However, chemicals have not been widely accepted by consumers in recent years due to their perceived adverse effects on health. Therefore, plant-derived ingredients and additives have been attracting interest as potential alternatives. Our research group previously reported novel α-helical propeptides (SnuCalCpIs) derived from the medicinal plant Calotropis procera R. Br, as potential candidates for antimicrobial preservatives. In the present study, their activity against four food spoilage yeasts was investigated. The antimicrobial peptide, SnuCalCpI15, exhibited minimum inhibitory activity of 0.20 ± 0.01, 0.20 ± 0.01, 0.26 ± 0.01, and 0.26 ± 0.01 mM against Candida albicans, Saccharomyces cerevisiae, Pichia anomala, and Rhodotorula mucilaginosa, respectively. Fluorescein isothiocyanate (FITC) labeling revealed that SnuCalCpI15 initially bound to yeast cell surfaces and then entered the cells. Increased cell membrane permeability was determined based on the LIVE/DEAD cell viability assay and propidium iodide (PI) uptake. Morphological changes in yeast cells, especially altered cell wall thickness, were investigated using transmission electron microscopy (TEM). The results indicated that SnuCalCpI15 is a potent alternative to chemical antifungal food preservatives, and can be used to improve the shelf life and quality of foods vulnerable to yeast spoilage.