Production and characterization of novel marine black yeast's exopolysaccharide with potential antiradical and anticancer prospects

Abstract

The marine black yeasts are characterized by the production of many novel protective substances. These compounds increase their physiological adaptation to multi-extreme environmental stress. Hence, the exopolysaccharide (EPS) producing marine black yeast SAHE was isolated in this study. It was molecularly identified as Hortaea werneckii (identity 98.5%) through ITS1 and ITS4 gene sequencing analysis. The physicochemical properties of the novel SAHE-EPS were investigated through FTIR, GC-MS, TGA, ESM, and EDX analysis, revealing its heteropolysaccharide nature. SAHE-EPS was found to be thermostable and mainly consists of sucrose, maltose, cellobiose, lactose, and galactose. Furthermore, it exhibited an amorphous texture and irregular porous surface structure. SAHE-EPS showed significant antiradical activity, as demonstrated by the DPPH radical scavenging assay, and the IC50 was recorded to be 984.9 μg/mL. In addition, SAHE-EPS exhibited outstanding anticancer activity toward the A549 human lung cancer cell line (IC50 = 22.9 μg/mL). Conversely, it demonstrates minimal cytotoxicity toward the WI-38 normal lung cell line (IC50 = 203 μg/mL), which implies its safety. This study represents the initial attempt to isolate and characterize the chemical properties of an EPS produced by the marine black yeast H. werneckii as a promising antiradical and anticancer agent.

Keywords: Anticancer; Black yeast; Chemical characterization; Exopolysaccharide; Hortaea Werneckii.

Fig. 1

Morphology of the marine black yeast isolate SAHE cells on SDA medium (a), scanning electron microscopy (SEM) image of SAHE yeast cells (b), and dried SAHE-EPS (c)

Fig. 2

Phylogenetic tree constructed according to the ITS partial gene sequence of the black yeast strain SAHE identified as Hortaea werneckii by BLAST (NCBI). The tree was constructed using the website https://www.phylogeny.fr

Fig. 3

FTIR spectrum of the purified exopolysaccharide produced by H. werneckii SAHE

Fig. 4

GC-MS chromatogram of the purified EPS produced by H. werneckii SAHE

Fig. 5

Surface morphology of H. werneckii SAHE EPS investigated under SEM at 100X (a), 250X (b), and 2,000X (c)

Fig. 6

SEM-EDX analysis of the EPS produced by H. werneckii SAHE

Fig. 7

TGA analysis of the EPS produced by H. werneckii SAHE

Fig. 8

Antiradical activity of the SAHE-EPS using the DPPH radical scavenging test

Fig. 9

Superoxide anion scavenging activity of SAHE-EPS (a), Ascorbic acid (b), and hydroxyl radical scavenging activity of SAHE-EPS (c), and Ascorbic acid (d)

Fig. 10

Cytotoxicity of SAHE-EPS (a) and Sorafenibon as a control (b) against normal human lung cell line (WI-38) and anticancer activity of SAHE-EPS (c) and Sorafenibon as a control (d) against human lung cancer cell line (A549)