Production and characterization of bioemulsifier from local isolate of Saccharomyces cerevisiae strain JZT351: Antioxidant and antimicrobial effects

Abstract

The widespread use and circulation of industrial emulsifiers pose significant health risks, compounded by their limited availability and high cost. Consequently, there is growing interest in exploring the potential of natural sources, such as microorganisms like yeast, for emulsifier production. In this study, 25 strains of Saccharomyces cerevisiae were isolated from 17 distinct local sources. The yeasts were characterized based on cell shape, size, and colony morphology using yeast malt agar, followed by morphological, microscopic, and biochemical analyzes. Among the isolates, AC1 from a vinegar starter demonstrated superior bioemulsifier production. Emulsification efficiency tests revealed that AC1 exhibited values of 7.1 cm, 0.71 nm, and 34.50%, outperforming other isolates. The biomass yield was approximately 4.35 g/L. This strain was registered in the gene bank as JZT351 (OR115510) after a 100% match with S. cerevisiae. Optimal bioemulsifier production conditions for JZT351 were identified using a liquid yeast extract peptone dextrose medium, with date juice replacing 75% of the glucose, at pH 5.5, 30°C, and 72 h. The resulting emulsification activity, index, and oil displacement were 8.69 cm, 0.95 nm, and 39.7%, respectively. Fourier-transform infrared spectroscopy (FTIR) compared the functional groups of the bioemulsifier with those of conventional emulsifiers. Molecular characterization was confirmed by 1H NMR. FTIR spectra revealed bioemulsifier bands at 3443.28, 2929.34, 1656.559, 1534.09, 807.06, and 1656.55 cm⁻¹. At 0.5–5 ppm, signals and spectral frequencies corresponded to a mannoprotein structure. The bioemulsifier exhibited 58.09% antioxidant activity at 10 mg/mL, as assessed by DPPH scavenging. It showed the highest inhibition against Pseudomonas aeruginosa and the least against Candida albicans.