Pellicle formation

 Aim

To demonstrate pellicle formation in a broth culture 

Principle

Homogenous suspended microbial growth in a liquid medium will aid in availability of oxygen and other nutrients. This is ensured by using a rotary shaker or impeller driven bioreactor that keeps the cell, product, substrate and oxygen well mixed. When agitation stops, the culture remains static and the dissolved oxygen in the culture broth gets quickly used up, restricting growth and encouraging anaerobic physiology. At the surface of the broth, due to oxygen availability from the above gaseous phase, cells continue to multiply forming a well textured physical mat known as pellicle at the liquid surface. This further cuts off any oxygen diffusing from the top, pushing the lower part to further anaerobiosis.

Pellicle formation can result in low yields in a bioprocess industry due to unintended channelling of the substrate and efforts since unwanted by-products will be formed and will complicate the downstream processing.

 Materials Required

1. Culture: Aspergillus niger

2. Media: Doelger Prescott broth

3. Routine microbiological facilities

 Procedure

1. Aspergillus niger was inoculated in 300 ml of Doelger Prescott media.

2. It was incubated for 6 hours in a rotary shaker and then at room temperature undisturbed for about 7 days.

3. After incubation, the culture broth was observed for pellicle formation.

Observation and Result

A thick mat of microbial growth was observed on the surface of the liquid media.