Biosynthesis of Levan by Halomonas elongata 153B: Optimization for Enhanced Production and Potential Biological Activities for Pharmaceutical Field

Abstract

Halophilic organisms are a novel attractive option as cell factories for the production of industrially valuable bioproducts. Halomonas elongata is the cell factory of choice for ectoine production, but its levan production has not been well researched. Based on this scientific motivation, in this study, we evaluated the chemical and biological properties of levan produced by the halophilic extremophile Halomonas elongata 153B (HeL). First, the central composite design was used to determine the optimal process variables for maximum levan biosynthesis. Then, the levan produced from HeL was purified, quantified, and chemically characterized with FTIR, ¹H-NMR, and GPC analyses. This was followed by antioxidant, anti-inflammatory, antibiofilm, and antimicrobial activity tests to assess its biological activities as well as a cytotoxcity assay. Maximum levan yields of 5.13 ± 0.38 g/L were achieved after dialysis at the optimum levels of process variables. The ¹H-NMR spectrum of HeL revealed characteristic signals. It showed a strong antioxidant activity of 67.88% and the best radical scavenger. At a concentration of 400 µg/mL, HeL showed the most anti-inflammatory efficacy. Also, at all indicated concentrations (250, 500, 750, and 1000 μg/mL) HeL, acted against biofilms formed by Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 11778, Candida albicans ATCC 10231. Furthermore, HeL displayed antimicrobial activities against all strains tested. Finally, HeL showed high Cell viability in all dosages and no cytotoxicity was observed. In light of these results, HeL may have high potential in the medical, pharmaceutical and dermo-cosmetics industries.