NISIN

Nisin is used as a food preservative. Nisin, is effective against a wide range of Gram-positive bacteria, both as vegetative cells and as spores.

Nisaplin is comercially produced food preservative. Its composition is

Nisin - 2.5%

Sodium Chloride - 77.5%

Protein - 12%

Carbohydrate - 6%

Moisture - 2%

It is an inhibitory polycyclic peptide with 34 amino acid residues

It contains the uncommon amino acids

lanthionine , methyllanthionine , dehydroalanine , dehydro-amino-butyric acid.

These special amino acids are synthesized by posttranslational modifications. (In these reactions a ribosomally synthesized 57-mer is converted to the final peptide.) The unsaturated amino acids originate from serine and threonine

Nisin is most stable in acid conditions.

Nisin is soluble in aqueous environments.

Some loss of activity is expected when nisin is used in heat-processed

foods.

Nisin is produced by fermentation using the bacterium Lactococcus lactis a bacterium which occurs naturally in milk.

Commercially it is obtained from natural substrates including milk and is not chemically synthesized.

It is used in processed cheese production to extend shelf life by suppressing gram-positive spoilage and pathogenic bacteria

There are many other applications of this preservative in food and beverage production

Due to its highly selective spectrum of activity it is also employed as a selective agent in microbiological media for the isolation of gram-negative bacteria, yeast and moulds

Subtilin and Epidermin are related to Nisin, all members of a class of molecules called lantibiotics. As a food additive, nisin has E number E234

Uses

Nisin was first introduced commercially as a food preservative in the UK approximately 30 years ago. First established use was as a preservative in processed cheese products and since then numerous other applications in foods and beverages have been identified. It is currently recognised as a safe food preservative in approximately 50 countries. The established uses of nisin as a preservative in processed cheese, various pasteurised dairy products, and canned vegetables will be briefly reviewed.

More recent applications of nisin include its use as a preservative in high moisture, hot baked flour products (crumpets) and pasteurised liquid egg. Renewed interest is evident in the use of nisin in natural cheese production. Considerable research has been carried out on the antilisterial properties of nisin in foods and a number of applications have been proposed.

Uses of nisin to control spoilage by lactic acid bacteria have been identified in beer, wine, alcohol production and low pH foods such as salad dressings.

Further developments of nisin are likely to include synergistic action of nisin with chelators and other bacteriocins, and its use as an adjunct in novel food processing technology such as higher pressure sterilisation and electroporation.

Production of highly purified nisin preparations and enhancement by chelators has led to interest in the use of nisin for human ulcer therapy, and mastitis control in cattle.

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XANTHAN GUM

Xanthan gum is a polysaccaride produced by Xanthomonas campestris. Xanthomonas campestris is a bacteria responsible for causing black rot to form on broccoli, cauliflower and other leafy vegetables. The bacteria form a slimy substance which acts as a natural stabilizer or thickener. The United States Department of Agriculture ran a number of experiments involving bacteria and various sugars to develop a new thickening agent similar to corn starch or guar gum. When Xanthomonas campestris was combined with corn sugar, the result was a colorless slime called xanthan gum. Xanthan gum is considered a polysaccharide in scientific circles, because it is a long chain of three different forms of sugar. What's important to know is that all three of these natural sugars are present in corn sugar, a derivative of the more familiar corn syrup. The Xanthomonas campestris bacteria literally eat a supply of this corn sugar under controlled conditions, and the digestion process converts the individual sugars into a single substance with properties similar to cornstarch

Xanthan gum is vegetarian

One of the most remarkable properties of xanthan gum is its capability of producing a large increase in the viscosity of a liquid by adding a very small quantity of gum, on the order of one percent.

In most foods, it is used at 0.5%, or even as low as 0.05%.

The viscosity of xanthan gum solutions decreases with higher shear rates; this is called pseudoplasticity.

Foods need high viscosity at low shear rates to be stable but, when consumed, they must not seem thick and heavy in the mouth. Due to the pseudoplastic properties of xanthan gum, it can seem thin in the mouth (fairly high rates of shear) but still have good stabilization properties.

Unlike other gums, it is very stable under a wide range of temperatures and pH, and is widely accepted as a safe food additive world wide

Xanthan gum is used as stabiliser, emulsifier,lubricating agent, thickening agent.

The other uses of Xanthan Gum are:

1. In foods, xanthan gum is most often found in salad dressings and sauces. It helps to stabilize the colloidal oil and solid materials found in these products.

2. Also used in frozen foods and beverages, xanthan gum creates the pleasant texture in many ice creams.

3. Xanthan gum prevents ice crystals from forming in ice creams, and also provides a 'fat feel' in low or no-fat dairy products.

4. Toothpaste often contains xanthan gum, where it serves as a binder to keep the product uniform.

5. Cosmetic manufacturers add a very small amount of xanthan gum to their cream-based products in order to keep the individual ingredients from separating.

6. Xanthan gum is also used in gluten-free baking. Since the gluten (found in wheat) must be omitted, xanthan gum is used to give the dough or batter a "stickiness" that would otherwise be achieved with the gluten.

7. Oil companies often use water as a lubricant for oil well pumps, but regular water is not very thick. A natural thickener such as guar gum or xanthan gum can be added to the water in order to increase its viscosity, or thickness. (You could think of this as turning tap water into 10W-40 motor oil). The thickened water keeps the drill parts lubricated and displaces more of the natural oil found in the deposit area.

Xanthan gum is often used whenever a gel-like quality is sought.

Those who suffer from gluten allergies should look for xanthan gum as an ingredient on the label.

Xanthan gum is capable of synergistic interactions with galactomannans and glucomannans

POLY HYDROXY BUTYRATE - PHB

Polyhydroxybutyrate () is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class. It was first isolated and characterized in 1925 by French microbiologist Maurice Lemoigne. PHB is produced by micro-organisms like Alcaligenes eutrophus or Bacillus megaterium ‘apparently in response to conditions of physiological stress’.

The polymer is primarily a product of carbon assimilation (from glucose or starch) and is employed by micro-organisms as a form of ‘energy storage molecule’ to be metabolized when other common energy sources are not available.

Microbial biosynthesis of PHB starts with the condensation of two molecules of acetyl-CoA to give acetoacetyl-CoA which is subsequently reduced to hydroxybutyryl-CoA. Hydroxybutyryl-coA is then used as a monomer to polymerize PHB.

Fig : synthesis of PolyHydroxyButyrate

The poly-3-hydroxybutyrate (P3HB) form of PHB is probably the most common type of polyhydroxyalkanoate, but many other polymers of this class are produced by a variety of organisms these include :

• poly-4-hydroxybutyrate (P4HB)
• polyhydroxyvalerate (PHV)
• polyhydroxyhexanoate (PHH)
• polyhydroxyoctanoate (PHO) and their copolymers.

PolyHydroxyButyrate as Plastic

Polyhydroxybutyrate has attracted much commercial interest as a plastic material because its physical properties are remarkably similar to those of polypropylene (PP), even though the two polymers have quite different chemical structures.

While PHB appears stiff and brittle, it also exhibits a high degree of crystallinity, a high melting point of about 180 °C. Most importantly, PHB is rapidly biodegradable, unlike PolyPropylene.

Two major factors inhibiting widespread use of PHB lie in its production costs, which are a lot higher than plastics produced from petrochemicals, and its brittleness, since PHB as it is currently produced cannot handle high impact.

There are also some concerns of how large quantities of PHB would affect the environment. In the future research using genetic technology may be able to produce a better bacteria-based plastic that has more desirable properties and is cheaper to produce. For example PHB production may become cheaper if researchers could find a way to make bacteria produce larger amounts of polymer within shorter time spans. Once PHB becomes as cheap as plastics produced from petrochemicals, then it will probably become widely used, since it has the potential to be employed for packaging products like bottles, bags, wrapping film and disposable nappies.

PHB is being also evaluated as a material for tissue engineering scaffolds and for controlled drug-release carriers owing to its biodegradability, optical activity and isotacticity.

Research & commercial activities around PHB

Given the wide interest into polyhydroxyalkanoates, research on PHB has been quite extensive both in academic and industrial centres. Within the last decade, a team at the DoE Plant research lab at Michigan State University genetically modified plants to enable them to produce PHB. In 1992 they took two genes from PHB-making bacteria and inserted them directly into two cress plants and then crossed them. Some of the offspring plants incorporated both the new genes and produced PHB in their leaves. They had managed to create a plant that could grow plastic. After further refinining of the process they managed to increase production within the plant without affecting growth: 14% of the dry weight of the genetically modified leaves is PHB. During the 1980s, by means of genetic engineering, the three genes responsible for PHB production in A.eutrophus were successfully transferred to the common bacterium E. coli as well, paving the way for recombinant bacterial synthesis.
In 1996 Monsanto (who sold PHB under the trade name Biopol) bought all patents for making the polymer from ICI/Zeneca. However, Monsanto's rights to Biopol were sold to the American company Metabolix in 2001 and Monsanto's fermenters producing PHB from bacteria were closed down at the start of 2004. The focus is now on producing PHB from plants instead of bacteria. But now with so much media attention on GM crops, there has been little news of Monsanto's plans for PHB.
In June 2005, a US company received the "Presidential Green Chemistry Challenge Award" (small business category) for their development and commercialisation of a cost-effective method for manufacturing PHAs in general, including PHB

BASIC INDUSTRIAL AND ENVIRONMENTAL BIOTECHNOLOGY syllabus, JNTU (2007-2008)

UnitI : Production of Primary Metabolites

A brief outline of processes for the production of some commercially important Organic acids (e.g. citric acid, lactic acid, acetic acid, gluconic acid,); Amino acids (Glutamic acid, lysine, aspartic acid&Phenylalanine); and Alcohols (ethanol, 2,3- butanediol)

UNIT II: Secondary Metabolites :

Study of production processes for various classes of low molecular weight secondary metabolites: Antibiotics-beta-lactams (Penicillins), semi synthetic Pencillins and Cephalosporins amino-glycosides (streptomycin), macrolids (erythromycin), quinines, and aromatics. Vitamin (B12) and Steroids, dual

or multiple fermentation.

Unit III: Production of Commercially Important Enzymes

Proteases, Amylases Lipases, Cellulases, Pectinases, Isomerases and other commercially important. Enzymes for the food pharmaceutical industries;

UNIT IV : Recombinant Proteins

Production of recombinant proteins (Insulin, Interleukin & Interferon’s ) having therapeutic and diagnostic applications; production of vaccines.

Unit V : Bio products and other Processes

Natural Biopreservatives (Nisin), and Biopolymers (Xanthan Gum and PHB); Single Cell Protein, Racemically-pure Drug Intermediates, Steroid Bioconversions; High -Fructose Corn syrup; Bioconversion of Vegetable Oils, Bioleaching.

Unit VI : Biological treatment of waste Water – Aerobic and Anaerobic Systems

Biological processes for domestic and industrial waste water treatments; Aerobic systems - activated sludge process, trickling filters, biological filters, rotating biological contractors (RBC), Fluidized bed reactor (FBR), expanded bed reactor, Inverse fluidized bed biofilm reactor (IFBBR) packed bed reactors air- sparged reactors ; Anaerobic Systems - contact digesters, packed column reactors, UASB.

Unit VII: Bioremediation

Introduction, constraints and priorities of Bioremediation, Biostimulation of Naturally occurring microbial activities, Bioaugmentation, in situ, ex situ, intrinsic & engineered bioremediation,Solid phase bioremediation - land farming, prepared beds, soil piles, Phytoremediation. Composting, Bioventing & Biosparging; Liquid phase bioremediation - suspended bioreactors, fixed biofilm reactors.

Unit VIII: Hazardous Waste Management

Introduction - Xenobiotic compounds, recalcitrance. hazardous wastes - biodegradation of Xenobiotics . Biological detoxification - hazardous waste management with at least 3 – 4 Examples.

TEXT BOOKS:

Biotechnology, 3rd edition by John E. Smith. Cambridge low price editions.

Industrial Microbiology: - J. E. Casida;

3 Environmental Biotechnology by S. K. Agarwal

4 Biodegradation & Bioremediation (1999), Martin Alexander, Academic press.

REFERENCES:

1.Microbiology: - Prescott and Dunn.

2.Microbial biotechnology: Glazer, A.N. and Nikaido, H. 1995 W.H. Freeman &Company, New York.

3. Industrial Microbiology:- A. H. Patel.. Stanier R. Y., Ingram J.L., Wheelis M.L., Painter R.R., General

Microbiology McMillan Publications, 1989.

4. Foster C.F., John Ware D.A., Environmental Biotechnology, Ellis Horwood Ltd.,1987.

5. Karrely D., Chakrabarty K., Omen G.S., Biotechnology and Biodegradation,

6. Advances in Applied Biotechnology Series, Vol.4, Gulf Publications Co. London, 1989.

7. Bioremediation engineering; design and application 1995 John. T. cookson,Jr. Mc Graw Hill, Inc.

8. Environmental Biotechnology by A.K. Chatterjee

9. Environmental Biotechnology by S.N.Jogdand Himalaya Publishing