Some raw materials used in preparation of industrial media (a) Corn steep liquor: It is a by-product of starch manufacture from maize. The lowered pH inhibits most other organisms, but encourages the development of naturally occurring lactic acid bacteria especially homofermentative thermophilic Lactobacillus spp. which raise the temperature to 38-55°C. Under these conditions, much of the protein present in maize is converted to peptides which along with sugars leach out of the maize and provide nourishment for the lactic acid bacteria.

- The pH is about 4 (by steeping SO) - The pH is about 4 (by steeping SO). Acid conditions soften the kernels and the resulting maize grains mill better while the gel- forming property of the starch is not hindered. The supernatant drained from the maize steep is corn steep liquor.

maize lowered pH Most other organisms &encourages lactic acid bacteria (homofermentative thermophilic Lactobacillus) 38-55°C By lactic acid bacteria protein present in maize peptides. Sugars leach out of the maize & provide nourishment for the lactic acid bacteria

Sugars leach out of the maize & provide nourishment for the lactic acid bacteria Steeping, add SO2 Acidic pH(4) Soften the kernels & the resulting maize grains mill & gel-forming property of the starch is not hindered Supernatant is corn steep liquor

Before using corn steep liquor: It must be filtered & concentrated by heat to about 50% solid concentration. The heating process kills the bacteria. It must be neutralized by CaCO3 because it highly acidic. -Corn steep liquor is being rich in carbohydrates, nitrogen, vitamins, & minerals.

(b) Pharmamedia This is a yellow fine powder made from cotton-seed embryo. It is used in the manufacture of tetracycline and some semi-synthetic penicillins . It is rich in protein, (56% w/v) and contains 24% carbohydrate, 5% oil, and 4% ash, the last of which is rich in calcium, iron, chloride, phosphorous, and sulfate.

(c) Distillers solubles This is a by-product of the distillation of alcohol from fermented grain. It is prepared by filtering away the solids from the material left after distilling fermented cereals (maize or barley) for whiskey or grain alcohol  The filtrate concentrated to about one-third solid content to give a syrup  syrup is then drum-dried  distillers soluble. It is rich in nitrogen, minerals, and growth factors.

The corn is unloaded & stored    Hammer mills grind the corn    water & enzyme are added to the flour  a slurry mash  The slurry mash enters a fermentation tank  yeast & a second enzyme are added  This enzyme breaks the complex sugars  glucose  The yeast convert the glucose  alcohol & carbon dioxide.  At this point the mash is called beer.  The beer is sent to distillation  the alcohol is heated & separates from the beer  sillage  pumped to the centrifuges  The liquid, called thin sillage  condensed by boiling  syrup syrup is then drum-dried  distillers soluble.  

d) Soya bean meal :It is an annual legume which is widely cultivated throughout the world in tropical, sub­tropical and temperate regions. The seeds are heated before being extracted for oil that is used for food, as an antifoam in industrial fermentations, or used for the manufacture of margarine. The resulting dried material, soya bean meal

Soya bean meal (dried material) Heating of seeds Extraction of oil Oil used as For margarine production For food Antifoam in industrial fermentations. Soya bean meal (dried material) ..

Composition of soya bean meal has about 11% N, 30% carbohydrate and may be used as animal feed. Its nitrogen is more complex than that found in corn steep liquor & is not readily available to most microorganisms, except Actinomycetes. It is used particularly in tetracycline and streptomycin fermentations

(e) Molasses It is a good source of sugar and is used in many fermentation industries including the production of potable and industrial alcohol, acetone, citric acid, glycerol, and yeasts, it is a by-product of the sugar industry.

(f) Sulfite liquor (waste sulfite liquor, sulfite waste liquor or spent sulfite liquor) It is the aqueous effluent resulting from the sulfite process for manufacturing cellulose or pulp from wood. Depending on the type, most woods contain about 50% cellulose, about 25% lignins & about 25% of hemicelluloses. During the sulfite process, hemicelluloses hydrolyze & dissolve hexose sugars, glucose, mannose, galactose, fructose, pentose sugars, xylose, & arabinose. The acid reagent breaks the chemical bonds between lignin and cellulose; subsequently they dissolve the lignin.

The presence of calcium ions provides a buffer and helps neutralize the strong lignin sulfonic acid. The degradation of cellulose yields glucose. Sulfite liquor is used : As a medium for the growth of microorganisms after being suitably neutralized with CaCO3 and enriched with ammonium salts or urea, and other nutrients. It has been used for the manufacture of yeasts and alcohol.

(g) Other Substrates Other substrates used as raw materials in fermentations are alcohol, acetic acid, methanol, methane, and fractions of crude petroleum. These will be discussed under Single Cell Protein.

GROWTH FACTORS Growth factors are materials which are not synthesized by the organism and therefor must be added to the medium. They usually function as cofactors of enzymes and may be vitamins, nucleotides etc. The pure forms are usually too expensive for use in industrial media. Growth factors are required only in small amounts.

WATER Water is a raw material of vital importance in industrial microbiology. It is required as a major component of the fermentation medium, as well as for cooling, washing & cleaning. It is therefore used in rather large quantities, and measured in thousands of liters a day depending on the industry. In some industries such as the beer industry the quality of the product depends to some extent on the water. In order to ensure constancy of product quality the water must be regularly analyzed for minerals, color, pH, etc. and adjusted as may be necessary.

The use of plant waste materials in industrial microbiology media Saccharification of polysaccharides Plant materials in general contain large amounts of polysaccharides which are not immediately utilizable by industrial microorganisms and which will therefore need to be hydrolyzed or saccharified to provide the more available sugars.

Starch Starch is a mixture of two polymers of glucose: amylose and amylopectin. Amylose is a linear (1 4)- D glucan usually having a degree of polymerization of about 400 and having a few branched residues. Lignin It is a complex three-dimensional polymer formed from cyclic alcohols. It is important because it protects cellulose from hydrolysis. Cellulose is found in plant cell-walls.

Cellulose Cellulose is the most abundant organic matter on earth. Unfortunately it does not exist pure in nature and even the purest natural form (that found in cotton fibers) contains about 6% of other materials. Three major components, cellulose, hemi-cellulose and lignin occur roughly in the ratio of 4:3:3 in wood.

Prepared by Dr Lina Jamil