Abstract

The marine environment is a promising source of microbial biodiversity that offers sustainable bioactive compounds for therapeutic and cosmeceutical applications. With the rising demand for eco-friendly alternatives and growing concerns over synthetic chemicals in skincare, natural products such as levan, a microbial exopolysaccharide, have gained attention for their moisturizing, antimicrobial, anti-aging, and prebiotic activities.

This study explored the microbes of El Hamra Lake, part of the hypersaline Wadi El-Natrun in Egypt, known for its extreme alkaline conditions (pH 8.5–11) and high salinity (91.0–393.9 g/L) for their levan production capabilities. Using microbiological and molecular techniques, twenty bacterial strains were isolated on two types of media, starch casein agar and casein nutrient agar, characterized based on their salt tolerance, and identified using 16S rRNA gene sequencing. Among them, four were halophilic and sixteen were halotolerant strains.

The isolates were screened for levansucrase activity, and the levan for each isolate was extracted and purified for further evaluation. The highest levan yield was obtained from A2 (Mesorhizobium sp.) and B7 (Bacillus pumilus), ranging from 166.8 g/L to 120.7 g/L, respectively, using a 10% sucrose medium. Structural confirmation was performed using NMR (1H and 13C) and FT-IR spectroscopy, confirming the β-(2→6)-linked fructan structure.

The extracted levans, particularly B10 and B15, exhibited notable antimicrobial activity against skin pathogens such as Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. Moreover, B14, B10, B15, and B7 levans demonstrated strong prebiotic effects in enhancing the growth of skin probiotics Lactobacillus plantarum and Lactobacillus acidophilus. Safety and efficacy were evaluated through cytotoxicity assays on Human Skin Fibroblast (HSF) cells, with the optimal therapeutic dose of 200 µg/mL. Levans A10 and B17 promoted HSF proliferation, resulting in the highest cell viability percentages of 495.57% and 452.70%, respectively.

These findings suggest that extreme environment-derived levan has great potential in the cosmetic industry. Its natural origin, human skin safety, moisturizing properties, and ability to support healthy skin microbiota make it a promising ingredient for the development of safe and effective skincare formulations/products. Additionally, it highlights the potential of Wadi El-Natrun’s microbes as a valuable source for eco-safe levan production, offering scalable, natural alternatives for cosmeceutical product development.

School

School of Sciences and Engineering

Department

Biotechnology Program

Degree Name

MS in Biotechnology

Graduation Date

Fall 2-17-2026

Submission Date

9-18-2025

First Advisor

Ahmed Moustafa

Second Advisor

Rania Siam

Third Advisor

Rehab Z. Abdallah

Committee Member 1

Walid Fouad

Committee Member 2

Nahla A. Hussein

Committee Member 3

Andreas Kakarougkas

Extent

74 p.

Document Type

Master's Thesis

Institutional Review Board (IRB) Approval

Not necessary for this item

Disclosure of AI Use

Thesis editing and/or reviewing

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Available for download on Saturday, September 18, 2027

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