Bacterial Fermentation Definition

Most energy-conserving reactions in living organisms are redox reactions. One substrate is oxidized with the concomitant reduction of another substrate. In chemoorganotrophic aerobes, the substrate reduced is usually oxygen. In respiring anaerobes, the electron acceptor can be either organic or inorganic. Typical examples are the sulfate-reducing or methanogenic organisms (carbon dioxide). In respiring organisms, both aerobic and anaerobic, most of the energy is produced by electron transport phosphorylation. This is in contrast to fermentations, in which most of the adenosine triphosphate (ATP) is synthesized by substrate level phosphorylation.

Fermentation is an anaerobic redox process, in which the oxidation of the substrate is coupled to the reduction of another substrate or an intermediate derived from the oxidation, with the difference in redox potential of the substrate and the end product providing energy for ATP synthesis. In most fermentations, the same substrate is used as both reductant and oxidant, whereas in some amino acid fermenting organisms, one amino acid is oxidized and another is reduced (Stickland reaction). The oxidation reaction is coupled to substrate level phosphorylation whereas the reduction reaction is usually not. The fermentation end products are excreted. The nature of these products is different in various species, and the various fermentation pathways are named after their main products.

High Cell-Density Fermentation

This is a 5-day protocol for high cell-density bacterial fermentation and overnight over-expression of (a) target protein(s) using a computer controlled fed-batch procedure.

Protocol in short
Day 1/td>	Assembly of the fermenter vessel Preparation and autoclavation of the fermenter vessel Preparation for autoclaving Calibration of the pH probe (external) Autoclaving the fermenter vessel Preparation of the starter culture
Day 2	Preparation of inoculation cultures Preparation of the fermenter vessel for cultivation Polarizing the DO probe (for at least 6 hours) Recalibration of the pH probe (internal) Setting the fermentation parameters Calibration of the DO probe Inoculation of the fermenter vessel and start of the batch phase
Day 3	Start of the fed-batch phase Start of the feeding protocol Induction of protein expression Start of the temperature profile IPTG induction
Day 4	Harvesting of the cells Harvesting the cells Cleaning the feed tubing Autoclaving the fermenter vessel
Day 5	Cleaning of the fermenter vessel

Microbial Fermentation Process

BIC(BiologicsCorp) has a number of 5L, 50L, 100L, and 1000L fermentors available on-site for fermentation runs. BIC’s fermentation services include:

• 5 L to 1000 L fermentors for process development
• High cell density fermentations
• Batch, fed-batch and perfusion capabilities
• Continuous flow centrifuge & hollow fibers for separation of biomass from broth
• Fermentation optimization