All microorganisms require water, sources of energy, carbon, nitrogen, mineral elements and possibly vitamins plus oxygen if aerobic.
a) It should produce the maximum yield of product or biomass per gram of substrate used.
b) It should produce the maximum concentration of product or biomass.
c) It should produce the maximum rate of product fermentation.
d) There should be minimum yield of undesirable products.
e) It should be of consistent quality and should be available throughout the year.
f) It should not cause much problem while media making and sterilization.
Water: It is a major component in fermentation media and is needed in heating, cooling, cleansing and rinsing. The mineral content of the water is very important in brewing, and most critical in the mashing process, and influences the siting of breweries and the types of beer produced. Nowadays, the water may be treated by deionization or other techniques, and salts added or adjusted, to favor different beers so that breweries are not so dependent on the local water source.
Energy sources: energy for growth comes from either the oxidation of medium components or from light. Most industrial micro-organisms are chemo-organotrophs; therefore the commonest source of energy will be the carbon source such as carbohydrates, lipids and proteins. Some micro-organisms can also use hydrocarbons or methanol as carbon and energy source.
Carbon source: the major carbon source which are used are carbohydrates namely starch, sucrose, lactose etc. Oils and fats may also be used as carbon source. Hydrocarbon and its derivatives also find their usage as carbon source in bioprocess technology.
Nitrogen source: most industrially used micro-organisms can utilize inorganic and organic source of nitrogen. Inorganic nitrogen may be supplied as ammonia gas, ammonium salts and nitrates. Organic nitrogen may be supplied as amino acid, protein or urea. Other proteinaceous nitrogen compounds serving as sources of amino acids include corn-steep liquor, soya meal, peanut meal, cotton-seed meal, Distillers’ soluble, meal and yeast extract.
Minerals: in many media, magnesium, phosphorus, potassium, sulphur, calcium and chlorine are essential components. Others such as cobalt, cooper, iron, manganese, molybdenum, and zinc are also essential but are usually present as impurities in other major ingredients.