Abstract
In the present study, galactan exopolysaccharide (EPS) from Weissella confusa KR780676 was evaluated for its potential to alleviate oxidative stress using in vitro assays and in vivo studies in Saccharomyces cerevisiae (wild type) and its antioxidant (sod1∆, sod2∆, tsa1∆, cta2∆ and ctt1∆), anti-apoptotic (pep4∆ and fis1∆) and anti-aging (sod2∆, tsa1∆ and ctt1∆)) isogenic gene deletion mutants. Galactan exhibited strong DPPH and nitric oxide scavenging activity with an IC50 value of 450 and 138 µg/mL respectively. In the yeast mutant model, oxidative stress generated by H2O2 was extensively scavenged by galactan in the medium as confirmed using spot assays followed by fluorescencent DCF-DA staining and microscopic studies. Galactan treatment resulted in reduction in the ROS generated in the yeast mutant cells as demonstrated by decreased fluorescence intensity. Furthermore, galactan exhibited protection against oxidative damage through H2O2 -induced apoptosis inhibition in the yeast mutant strains (pep4∆ and fis1∆) leading to increased survival rate by neutralizing the oxidative stress. In the chronological life span assay, WT cells treated with galactan EPS showed 8% increase in viability whereas sod2∆ mutant showed 10–15% increase indicating pronounced anti-aging effects. Galactan from W. confusa KR780676 has immense potential to be used as a natural antioxidant for nutraceutical, pharmaceutical and food technological applications. As per our knowledge, this is the first report on in-depth assessment of in vivo antioxidant properties of a bacterial EPS in a yeast deletion model system.
Highlights
In the present study, galactan exopolysaccharide (EPS) from Weissella confusa KR780676 was evaluated for its potential to alleviate oxidative stress using in vitro assays and in vivo studies in Saccharomyces cerevisiae and its antioxidant, anti-apoptotic and anti-aging) isogenic gene deletion mutants
EPS production from W. confusa KR780676 was observed on MRS agar plate enriched with 2% sucrose, incubated for 48 h (Fig. 1A-i), which revealed Weissella slimy colonies and it was further confirmed in scanning electron microscopy (SEM) image showing presence of galactan EPS along with cells (Fig. 1A-ii)
Our results show a high sensitivity of yeast glr1∆ to H 2O2 which was alleviated by pre-treatment with galactan EPS suggesting that galactan EPS might protect the cells that are deficient of GLR1 from oxidative stress
Summary
Galactan exopolysaccharide (EPS) from Weissella confusa KR780676 was evaluated for its potential to alleviate oxidative stress using in vitro assays and in vivo studies in Saccharomyces cerevisiae (wild type) and its antioxidant (sod1∆, sod2∆, tsa1∆, cta2∆ and ctt1∆), anti-apoptotic (pep4∆ and fis1∆) and anti-aging (sod2∆, tsa1∆ and ctt1∆)) isogenic gene deletion mutants. Antioxidants are the molecules which scavenge free radicals generated in food or living system and leading to the prevention of oxidative damage related health conditions[7,8,9]. The galactan EPS is screened for in vitro antioxidant potential using DPPH, nitric oxide and hydroxyl radical scavanging assays and in vivo antioxidant, anti-apoptotic and anti-aging properties using yeast gene deletion mutant model system
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