Preservation of industrial microorganisms 1- As slopes (kept in the refrigerator)2- Lyophilization (bacteria orfungal spores) are suspended in a suitable medium, quick freezing then dryingunder vacuum with survival rate of about 50% , stored for many years withoutloss of viability 3- Soil culture (sterile moist soil is mixed with suspension of fungal orbacterial spores, dried in desiccators, stored for many years) 4- Paraffin seal method (activelygrowing cultures are covered with 1 cm layer of sterile paraffin oil, forcultures that do not stand drying) 5- Quick freezing method (cultures are quicklyfrozen and held at -20°C or less up to -80°C in the presence of glycerol toreduce damage due to freezing) Fermentation medium The nutritional needs of microorganisms are diverse. The Fermentationmedium consists of: 1- Macronutrients (C, H, N, S, P, Mg sources in water,sugars, lipids, amino acids, salts, minerals) 2- Micronutrients (traceelements/ metals, vitamins) 3- Additional factors: growth factors, attachmentproteins, transport proteins, etc). 4- For aerobicculture, oxygen is also included 5- Precursors:Directly incorporated into the desired product: Phenyl acetic acid intoPenicillin G 6- Inhibitors: To getthe specific products: e.g. Sodium barbital for Rifamycin 7- Inducers: Majorityof the enzymes are inducible and are synthesized in response to inducers: e.g.Starch for Amylases, Pectin for Pectinase 8- Chelators: are thechemicals used to avoid the precipitation of metal ions. Chelators like EDTA,Citric acid, are used in low concentrations.
9- Trace elements :Fe, Zn, Cu, Mn, Mo, Co 10- Antifoaming agents: Esters, Fatty acids, Silicones,Sulphonates, Polypropylene 11- Buffers: Calcium carbonate, Phosphates 12- Growth factors: Some microorganisms cannot synthesize therequired cell components themselves and need to be supplemented: E.g. Thiamine,Biotin, Calcium pentothenate Submersion technique In the submersion processes, the microorganisms grow in aliquid medium. The medium is held in fermenters and stirred to obtain ahomogeneous distribution of cells and medium. All-important industrial processes (production of biomass andprotein, antibiotics, and enzymes) are carried out by submersion processes. The submersion processes may be run in: Batch – fed batch –continuous 1- Batch fermentation: Most fermentations are batch processesBatch processing or batch culture: Nutrients andthe inoculum are added to the sterile fermentor, fermentation process isallowed to proceed for limited time under controlled conditions from aerationand agitation, etc After certain incubation period (the desiredamount of product is present) the process stopped, yield recovered, the tank iscleaned and a new batch is set up.The best advantage of batch processing is the optimumlevels of product recovery. However the disadvantages are the wasting of unusednutrients, and the time lost between batches.
2- Fed batchfermentation process: In the fed-batch system, a fresh aliquot of themedium is continuously or periodically added, without the removal of theculture fluid that has the advantage of avoiding the toxic effects of a mediumcomponent.?The production of penicillin, as a secondarymetabolite, is best done by fed-batch method. The culture is maintained at lowlevels of biomass and phenyl acetic acid (PAA), the precursor of penicillin, isfed into the fermentor continuously, but at a low rate, as the precursor istoxic to the organism at higher concentrations 3- Continuous processing or culture (Chemostat ) Fermentationprocess allowed to proceed continuously with continuous supply of requirednutrients and products are withdrawn regularly. Nutrients are added to thefermentation vessel and products are withdrawn at the same rate Primary and Secondary Metabolites: Primarymetabolites are produced during active cell growth They include Intermediates in metabolic pathways(TCA cycle, pathways leading to protein and nucleic acid production) Secondary metabolites are produced near the onset of stationary phase Theyare not part of the “central” metabolic pathways .
Therefore they are notessential for growth. Examples include: Actinomycetes (eg Streptomyces),Fungi (eg Penicillium) ,Sporeforming bacteria (Bacillus) Secondary metabolites are produced as growthslows/stops in batch cultures .Antibiotics are of major industrial importance Antibiotics are compounds produced naturally from somemicroorganisms that kill or inhibit the growth of other microbes. They are typicallysecondary metabolites . Most antibiotics in clinical use are produced byfilamentous fungi or actinomycetes Microbesare obtained from nature in pure culture Antibiotics are produced industrially by the process offermentation, where the source microorganism is grown in large containers(100,000 – 150,000 liters or more) containing a liquid growthmedium.