Synthesis and molecular characterization of levan produced by immobilized Microbacterium paraoxydans

Area of Science:

• Microbiology
• Biochemistry
• Biotechnology

Background:

• Microbacterium paraoxydans is known for fructooligosaccharide production.
• Levan, a high molecular weight fructan, has various industrial applications.
• Efficient microbial production of levan is desirable for commercial use.

Purpose of the Study:

• To investigate high molecular weight (HMW) levan production by Microbacterium paraoxydans.
• To characterize the structure and properties of the produced levan.
• To optimize levan production through cell immobilization and process parameter adjustments.

Main Methods:

• Whole cells of Microbacterium paraoxydans were used for extracellular levan production.
• Structural analysis determined the glycosidic linkage (β-(2, 6)) and molecular weight distribution.
• Cell immobilization in Ca-alginate and One-Factor-At-a-Time (OFAT) analysis were employed for optimization.

Main Results:

• The produced fructan was identified as HMW levan with β-(2, 6) glycosidic linkages.
• Over 90% of the levan exhibited a molecular weight of approximately 2 × 10⁸ Da.
• Immobilized cells produced 44.6 g/L levan, which increased to ~129 g/L under optimized conditions (400 g/L sucrose, pH 7, 37°C, 20 mM CaCl₂).
• Optimized conditions yielded a levan yield of ~0.41 g/g sucrose consumed and volumetric productivity of 1.8 g/L/h.

Conclusions:

• Microbacterium paraoxydans is a suitable microorganism for HMW levan production.
• Cell immobilization and optimized conditions significantly enhance levan yield and productivity.
• The study demonstrates a viable strategy for the efficient microbial synthesis of levan.