Microbial Biotechnology

Autoclaving: Autoclaving is a common method for sterilizing growth media. The media is heated to a high temperature (usually 121°C) under high pressure (15 psi) for 15-20 minutes in an autoclave. This ensures that microbes and spores are killed in the growth media.

Membrane Filter Sterilization: Another common method involves filtering the media with a membrane filter. Here, the media is forced through a membrane with a very fine pore size (0.2 or 0.22 micrometer pore size). This process physically removes microbes from the media, making it sterile for use in the lab.

Viable Plate Count Method: In this method, the number of living cells in a microbial culture are counted by the number of colonies that grow after being plated in a petri dish. The colony forming units (CFUs) give a measure of how many cells are growing in the original culture.
Turbidity Measurement: A spectrophotometer can be used to measure the turbidity or optical density of a microbial culture. The absorbance of the culture at a certain wavelength is proportional to cell concentration. This method is useful for quick and easy estimation of cell density.
Coulter Counter: A Coulter counter is a device that can count cells directly as they pass through a narrow pore. This provides a direct reading of the cell number, and is often used to measure cell count in a suspension.
Dry Weight: In this technique, the weight of the fixed volume of culture is measured after drying. It gives a direct estimate of the biomass.
Wet Weight: Here, the wet weight of a fixed volume of the culture is directly measured.
ATP Measurement: ATP concentration in a cell culture is measured by using ATP bioluminescence assay.

Penicillium chrysogenum: Penicillium chrysogenum} is the species of fungus that is most commonly used for the commercial production of the antibiotic penicillin. Through selective breeding and genetic manipulation, improved strains of P. chrysogenum} have been developed to produce higher concentrations of penicillin.

Penicillium notatum: Penicillium notatum} was the first species where the antibiotic properties of penicillin were discovered by Alexander Fleming, but this is not the most commercially used variety.

Penicillium eutrophus: Penicillium eutrophus} is not known for producing penicillin, and it is not commercially used in the production of penicillin.

Penicillium cerevisiae: Penicillium cerevisiae} is the scientific name for the baker’s yeast and it is a fungus used in bread production. It does not produce penicillin.

Continuous Culture System: In a continuous culture system, fresh nutrient medium is continuously added to the microbial culture vessel at a constant rate, while culture broth containing microorganisms, waste products, and unused nutrients is simultaneously removed at the same rate to keep the culture volume constant. This maintains the microorganisms in the exponential growth phase for extended periods.

Maintenance: - Use of a chemostat or similar device to control the flow rates of input and output. - Growth rate is controlled by the rate of nutrient supply (dilution rate). - Environmental conditions like pH, temperature, and oxygen are kept constant.

Advantages over Fed-batch Culture:

• Maintains microorganisms in a steady-state exponential growth phase, leading to consistent product formation.
• Allows precise control over growth rate and nutrient limitation.
• Enables long-term cultivation without the accumulation of inhibitory waste products.
• Higher productivity and better process control compared to fed-batch, where nutrient addition is intermittent.