BT603 Final Term Past Papers 4 in 1

VU Medical Zone · Amaan Khan · BT 603 Fermentation Technology · Lecture 38 to 73 · Final term Merge ppt · Media for · When certain inhibitors are added to fermentations, more · of a specific product may be produced, or a metabolic

intermediate which is normally metabolized is accumulated.

One of the earliest examples is the microbial production of · glycerol. Glycerol production depends on modifying the · ethanol fermentation by removing acetaldehyde. The · addition of sodium bisulphite to the broth leads to the · formation · of · the · acetaldehyde · bisulphite · addition · compound · (sodium · hydroxy · ethyl

sulphite).

Since · acetaldehyde is no longer available for re-oxidation of · NADH2, its place as hydrogen acceptor is taken by · dihydroacetone phosphate, produced during glycolysis. The · product of this reaction is glycerol-3-phosphate, which is

converted to glycerol. The application of general and specific inhibitors are illustrated in Table (in next slide). In most cases the inhibitor is effective in increasing the yield of the desired product and reducing the yield of undesirable related products.

A number of studies have been made with potential chlorination inhibitors, e.g. bromide, to minimize chlortetracycline production during a tetracycline fermentation.

Product · Inhibitor · Main effect · Glycerol · Sodium · bisulphate · Acetaldehyde pro- · duction repressed

Saccharomyces cerivisiae

Tetracycline · Bromide · Chlortetracycline · formation · repressed

Streptomyces aureofaciens

Glutamic acid Penicillin · Dell wall · permeability

Micrococcus glutamicus

Citric acid · Alkali metal/ · phosphate, pH · below 2.0 · Oxalic acid · repressed

Aspergillus niger

Valine · Various inhibitors Various effects · with different

Brevibacterium roseum

Rifamycin B · Di-ethyl · barbiturate · Other rifamycins · inhibited

Nocardia mediterranel

Specific and General Inhibitors used in fermentations

Inhibitors have also been used to affect cell-wall structure and increase the permeability for release of metabolites. The best example is the use of penicllin and surfactants in glutamic acid

END

Media for · INDUCERS-1 · The majority of enzymes which are of industrial interest · are

inducible.

Induced

enzymes

are synthesized only in response to the presence in the environment of an inducer. Inducers are often substrates such as starch or dextrins for amylases, maltose for pullulanase and pectin for pectinases.

Some · inducers · are · very

potent,

such

as inducing

nitralase. Substrate analogues that are not attacked by the enzyme may also serve as enzyme inducers. Examples of industrially important enzyme inducers are shown in Table given in next slide.

Some examples of industrially important enzyme inducers · Enzyme · Inducer · α-Amylase · Starch Maltose

Aspergillus spp. Bacillus subtilis

Pullulanase

Maltose

Aerobacter aerogenes

α-Mannosidase

Yeast mannans

Streptomyces griseus

Penicillin acylase

Phenylacetic acid

Escherichia coli

Proteases

Various proteins

Bacillus spp. Streptococcus spp. Streptomyces spp. Aspergillus spp.

Cellulase

Cellulose

Trichoderma viridae

Pectinases · Pectin · (beet pulp, apple · pomace, citrus peel)

Aspergillus spp.

Nitralase

Rhodococcus rhodochrous One unusual application of an inducer is the use of yeast mannan in streptomycin production. During the fermentation varying amounts of streptomycin and mannosidostreptomycin are produced.

Since mannosidostreptomycin has only 20% of the biological activity of streptomycin, the former is an undesirable product.

The production organism Streptomyces griseus can be induced by yeast mannan to produce β-mannosidase which

will · convert · mannosidostreptomycin

to streptomycin.

Most inducers which · are included in · microbial enzyme · media are substrates or

substrate analogues,

but intermediates and · products may · sometimes be used as

inducers. For example,

maltodextrins will · induce amylase and · fatty acids induce · lipase. However, the · cost may prohibit their · use as inducers in a

commercial process.

END The types of antifoams mentioned in previous slides are generally added when foaming occurs during the fermentation. Because many antifoams are of low solubility they need a carrier such as lard oil, liquid paraffin or castor oil, which may be metabolized and affect the fermentation process.

END