What is meant by ‘Fermentation’

• In the biochemical sense: fermentation refers to a metabolic process in which organic compounds particularly CHO are broken down to release energy without the involvement of a terminal electron receptor as Oxygen

Fermentation

• Partial oxidation of the substrate occurs & a small amount of ATP energy is released

• Partial oxidation of CHO give rise to a variety of organic compounds

• The compounds produced by microorganisms vary from organism to organism and are produced via different metabolic pathways

Industrial Fermentation

• This term is applied to any industrial process that produces a material useful to humans if the process depends on the activity of one or more microorganisms

• These processes are usually carried out in large scale

• Some are fermentations in the biochemical sense but the majority are aerobic processes in which the microorganism uses Oxygen and metabolizes CHO completely

What is produced by Industrial Fermentation

• Organic chemicals: fuels, food additives (Vinegar), antibiotics and enzymes for use in food and other industries

• Organisms for the extraction of proteins: Single Cell Proteins (SCP) can be part of human diet (Quorn from fungus) in meatless dishes

What is produced by Industrial Fermentation

• Yeast cells used in baking industry (baker’ s yeast)

• Large scale production of cheeses, yoghurt and bread

• Alcoholic beverages

Fermentation Process

Fermentation Raw Materials Production Microorganism

Fermentation

Product Purification

ProductEffluent Wastes

Downstream Processing

Upstream Processing

Cell culture fermenter

Shake flask fermenter

laboratory fermenter

Pilot fermenter Plant fermenter

Some important fermentation Some important fermentation productsproducts

Product Organism Use

Ethanol Saccharomyces cerevisiae

Industrial solvents, beverages

Glycerol Saccharomyces cerevisiae

Production of explosives

Lactic acid Lactobacillus bulgaricus

Food and pharmaceutical

Acetone and butanol

Clostridium acetobutylicum

Solvents

-amylase Bacillus subtilis Starch hydrolysis

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Upstream ProcessingUpstream Processing

• Three main areas: • A) Producer microorganism• This include processes for• obtaining a suitable microorganism• strain improvement to increase the

productivity and yield• maintenance of strain purity• preparation of suitable inocullum• B ) Fermentation media• C) Fermentation Process

Downstream ProcessingDownstream Processing

The processes that follows fermentation:

A) Cell harvestingB) Cell disruptionC) Product purification from cell

extracts or the growth medium

Carbohydrates usually act as both, sources of energy and building blocks for the synthesis of macromolecules, and also supply with oxygen and hydrogen.

Starch is a source of readily available energy and serves as building blocks for the growing plant. Starch occurs in two forms, a linear molecule called amylose and a branched molecule called amylopectin. Amylose consists of glucose units bound by cu(l,4)-linkages whereas amylopectins are branched chains bound by cu(1,6) linkages to the cu(l,4)-chain.

Different steps can be used to obtain starch or starch-derived products. Products from glucose oligosaccharides to simple monomers can be obtained from starch. The main technologies involved are enzyme conversions such as liquefaction, saccharification or isomerization, separation processes such as screening, sifting, centrifugation, chromatography or crystallization, and chemical transformations like hydrogenation or epimerization

A fermentation substrate must be readily available throughout most of the year. Raw materials produced seasonally are not desired if the harvesting period is short and the material to be used is subject to contamination and spoilage. Thus many industries need a substrate which is relatively stable and can be stored for 6-9 months without decomposition.

The Complex CarbohydratesThe Complex Carbohydrates

Starches◦Storage form of glucose in plants◦Found in grains, tubers, and legumes

All micro-organisms require watersources of energycarbonnitrogenmineral elementspossibly vitaminsoxygen if aerobic.

On a large scale one must normally use sources of nutrients to create a medium which will meet as many as possible of the following criteria:It will produce the maximum yield of product or biomass per gram of substrate used.It will produce the maximum concentration of product or biomass.It will permit the maximum rate of product formation.There will be the minimum yield of undesired products.It will be of a consistent quality and be readily available throughout the year.It will cause minimal problems during media making and sterilization.It will cause minimal problems in other aspects of the production process particularly aeration and agitation, extraction, purification and waste treatment.

The use of cane molasses, beet molasses, cereal grains, starch, glucose, sucrose and lactose as carbon sources, and ammonium salts, urea, nitrates, corn steep liquor, Soya bean meal, slaughter-house waste and fermentation residues as nitrogen sources, have tended to meet most of the above criteria for production media because they are cheap substrates. However, other more expensive pure substrates may be chosen.

A medium with a high viscosity need a higher power input for effective stirring.

Besides meeting requirements for growth and product formation, the medium may also influence pH variation, foam formation, the oxidation-reduction potential, and the morphological form of the organism.

Undefined complex natural materials have been used in fermentation processes because they are much cheaper than pure substrates.

Undefined media often make product recovery and effluent treatment more problematical because not all the components of a complex nutrient source will be consumed by the organism.

Although manufacturers have been reluctant to use fined media components because they are more expensive, pure substrates give more predictable yields from batch to batch and recovery, purification and effluent treatment are much simpler and therefore cheaper.

Process improvements are also easier to detect when pure substrates are used.

Starches are degraded in three steps:

Gelatinization-is the process by which the starch molecules break open, allowing them to be more readily converted by amylase enzymes.

Liquefaction- is the process by which the starch absorbs water, and the process is enzymatically driven by alpha-amylase.

Saccharification- the process of breaking a complex carbohydrate (as starch or cellulose) into its monosaccharide components

Economic Issues of Bioprocess Technology

Price is nevertheless an overriding consideration, particularly at the bulk end of the market with its heavy reliance on raw materials costs and product price elasticity

Production of agricultural raw materials is seasonal and therefore storage is essential, adds to costs as does as transport

Water content of a material is often a significant factor in transport costs

For a raw material price to be attractive it should be low, steady and predictable prices

several biotechnological raw materials are not used at all or are only used to a very limited extent, because their market price is much too high for economical use and because they have to compete with artificial raw materials, which might produce adverse environmental effects.

Impact of price fluctuations can in part overcome by trading in futures in a commodity market, where this exists or longer term fixed proce contracts

Price is determined in part by production costs (except with wastes and by-products), by transport and storage costs and by opportunity costs (or value in alternative uses)

Production costs of biomass products are associated with farm income, which may be the subject of laws or tariffs and is highly political

Opportunity costs frequently pertain to food applications and again may be in the political arena

Economic Issues of Bioprocess Technology

Availability of biomass is dictated by land use and yield, storage capability and markets

Land use is determined by price or expected price Major criterion in substrate value is the form and

availability of the carbon source The utility of cellulosic and lignocellulosic biomass is

restricted by hydrolysis to constituents sugars Most organisms are unable to achieve this or can only do it

slowly Alternative enzyme, chemical or physical methods are too

expensive Utility of whey is restricted by the inability of most

organisms to utilize lactose or galactose

Economic Issues of Bioprocess Technology

Many countries in the world are still deficient in fossil raw materials

Therefore, they are interested in establishing industries exploiting renewable resources for energy production and use as raw materials

The impact of CO2 as a causative agent of the greenhouse effect has increased interest in replacing fossil resources by renewable raw materials.

It is, therefore, necessary to identify potential renewable feedstock for basic chemicals and energy.

Biomass with a spectrum of products might be an alternative to fossil hydrocarbons such as oil, natural gas, and coal which were the basis of growth in the petrochemical industry during the last few decades.

The role of biotechnology in such a different economic situation is not clearly defined yet, but with the introduction of renewable resources as feedstock and mild process conditions this technology will probably be preferred.