A mycelium with polyelectrolyte complex-bunched hyphae: preparation and fermentation performance.

Area of Science:

• Biotechnology
• Microbial Immobilization
• Biocatalysis

Background:

• Mycelium immobilization is crucial for efficient biocatalysis.
• Traditional methods face challenges in achieving high cell density and activity.
• Aspergillus niger is a key microorganism for producing valuable compounds like gluconic acid.

Purpose of the Study:

• To develop a novel method for immobilizing Aspergillus niger mycelium using a polycation-polyanion complex.
• To investigate the effect of this immobilization on cell structure and sedimentation properties.
• To evaluate the impact of immobilization on the production of gluconic acid from glucose.

Main Methods:

• Utilized potassium poly(vinyl alcohol) sulfate as the polyanion and trimethylammonium glycol chitosan iodide as the polycation for mycelium immobilization.
• Employed optical and electron microscopy to analyze the structure of immobilized cells.
• Conducted semi-large scale (1L) fermentations in a jar fermentor to compare gluconic acid production by immobilized and free cells.

Main Results:

• Microscopic analyses confirmed the formation of polyelectrolyte complex (PEC)-bunched hyphae in the immobilized cells.
• Sedimentation rate of immobilized cells increased with the PEC to dry cell weight ratio, stabilizing above 0.5.
• Immobilized Aspergillus niger exhibited a 1.44-fold higher apparent specific activity for glucose oxidation compared to free cells at high cell densities (40 g/l).

Conclusions:

• The developed polycation-polyanion complex method effectively immobilizes Aspergillus niger mycelium.
• Immobilization enhances the catalytic activity of Aspergillus niger for glucose oxidation, leading to increased gluconic acid production.
• This technique shows promise for improving the efficiency of industrial bioprocesses utilizing microbial cells.