Candidate Acetic Acid Bacteria Strains for Levan Production

Area of Science:

• Microbiology
• Biochemistry
• Bacterial Metabolism

Background:

• Levan is a fructan polysaccharide with various industrial applications.
• Acetic acid bacteria (AAB) are known producers of exopolysaccharides, including levan.
• Understanding the factors influencing levan production is crucial for optimizing its yield.

Purpose of the Study:

• To investigate the levan production capabilities of twelve acetic acid bacteria (AAB) strains from five genera.
• To characterize the produced fructan as levan using NMR spectroscopy.
• To evaluate the effect of different sucrose concentrations (70 and 250 g/L) on levan yield.

Main Methods:

• Cultivation of twelve AAB strains under varying sucrose concentrations.
• Characterization of the produced fructan using Nuclear Magnetic Resonance (NMR) spectroscopy.
• Analysis of levan yield in relation to sucrose concentration, glucose accumulation, and pH changes.

Main Results:

• Most tested AAB strains produced levan, with significant intra- and inter-species variability.
• High levan yields were observed for *Neoasaia chiangmaiensis*, *Kozakia baliensis*, and *Gluconobacter cerinus* at 70 g/L sucrose.
• *N. chiangmaiensis* showed a 12-fold increase in levan production at 250 g/L sucrose.
• Levan production was negatively affected by glucose accumulation and pH reduction in *Ko. baliensis*.
• *Gluconobacter* strains showed a negative correlation with increased sucrose concentration, while *Komagataeibacter* strains showed no clear effect.

Conclusions:

• Levan yield among AAB strains is highly variable and influenced by culture conditions.
• Sucrose concentration, glucose accumulation, and pH are critical factors affecting levan production.
• The relationship between levan yield and sucrose concentration is not always direct, indicating complex regulatory mechanisms.