Optimization of fermentations, Biology tutorial


For some thousand years, fermentation has been a main method of preserving the food. Microbial growth, either of natural or inoculated population, causes chemical and/or textural modifications to form a product which can be stored for expanded periods. The fermentation procedure as well is to make new, pleasing food flavors and odors. The main fermentation is employed in microbiology are the lactic, ethanolic, propionic fermentations. Such fermentations are taken out by a broad range of cultures, most of which have not been characterized.

Alcoholic Beverages:

Microbes play important role in the production of alcoholic beverages like wine, beer, vodka, brandy, whisky and so on. The production of such beverages is illustrated below:

1) Beer production:

The brewing method begins with the malting of the grain followed through the conversion of the malted grain to soluble extract that is fermented through yeast to yield beer. The method employed find out the quality and the kind of beer produced. Careful control must be exercised at each phase of production to produce a beer of suitable standard.

Barely beer can be categorized into two wide groups:

(a) Top-fermented beer (ales)

(b) Bottom-fermented beer (lager)

This difference is mainly based on whether the yeast remains at the top of the brew (that is, top-fermented beer) or sediment to the bottom (that is, bottom-fermented beer) at the end of fermentation.

Brewing yeast strains are of two main kinds, that is, the top-fermenting and the bottom fermenting yeast. The top fermenting yeast remains equally distributed in the fermenting wort and are taken to the top by the CO2 gas produced throughout fermentation while bottom yeast  settle to the bottom. Top yeasts are employed in the brewing of ales and bottom yeasts are employed to make lager.

The bottom yeasts are generally given the species designation Saccharomyces carlbergensis and the top yeast are termed as Saccharomyces cerevisiae. Fermentation through top yeasts generally takes place at high temperature, 14 to 23oC whereas fermentation by bottom yeast takes place at 6 to 12oC.


Fermentation is achieved in a shorter time period (5 to 7 days) for top fermentation whereas it takes around 8 to 14 days for bottom fermentation. The brewing method, particularly production of barley beer comprises the given unit operations.

i) Malting: This is taken out to encourage synthesis of hydrolytic enzymes like alpha amylase, endo-β gluconase and peptidases to solubulize the endosperm wall of the grain and secure the enzymytic breakdown of the soluble component to low molecular weight. 

The malting method therefore gives sugar for the yeast from which it gets energy and amino acids for its growth. Malting comprises 3 methods: Steeping, germination and kelming.

ii) Marshing: This is the central method of brewing and comprises of mixing the malt by adjuncts at temperature that are optimum for the saccharomytic and proteolytic enzymes present in the malt. The specific marshing method employed is of optimus significance to the character of the resultant beer. There are three broadly contrasting mashing methods: Infussion marshing, Decoction marshing and double-marsh method.

iii) Fermentation: The filtered-cooled wort (15oC) is pumped to fermentation vessels that are a lot made up of stainless steel. This is pitched by yeast (0.2kg/hl on its way to the fermentation vessel). The fermentation continues for the desired number of days based on the kind of beer, throughout which a few fermentable sugars are transformed to CO2, glycerol, acetate and ethanol.

iv) Lagering and ageing: At the last part of fermentation, the product is beer and it consists of a harsh taste and termed to as 'green beer'.

v) Bottling: The filtered beer is pumped to the bottling hall for bottling. A few breweries, the beer are carbonated to the extent of 0.45 to 0.50% by weight.

vi) Pasteurization: Filled and cannel bottles are pasteurized prior to labeling.

2) Wine Production:

The word wine signifies to the alcoholic beverage made up from the juice of diversity of fruits through the fermentative action of chosen yeast adapted to the specific kind of wine followed by the ageing method. The word is often employed to demote the alcoholic beverage made up from grape fruit. The yeast employed in the fermentation of grape wine is Saccharomyces cerevisiae var. ellipsoideus that have been chosen over the years. There are two kinds of grape wine namely: Red wine and White wine.

Red wine that are fermented by the skin (red, purple) that comprise of the authocyanin pigment whereas white wine are generated from white grape or the juice of other grapes fermented devoid of their skin.

3) Spirit:

They are distilled liquor achieved from the fermentation of yeast of different carbohydrates having some raw materials example: sugarcane, grains and other plant materials. Distilled liquor comprises whiskey from barley, malt water, rice and oats. Bourbon from corn, gin from grain, malt flavored by jumper berries, rum from grains aquavit from grains flavored by caraway seed, and vodka from grain. The manufacturing step in the spirit industry comprises of raw material preparation, yeast propagation, fermentation and the treatment of fermented liquor and in several cases maturation or ageing.

Bread Baking:

The utilization of yeast as a leavening agent in the baking dates back to the much early history of the Egyptians, Jews, Greeks and Romans. In modern baking practice, pure cultures of chosen strains of Saccharomyces cerevisiae are mixed up with bread dough to make about desire modifications.

Desirable features of S. cerevisiae chosen from commercial production of baker's yeast comprise the capability to ferment sugar in the dough vigorously and to grow quickly. This is also other features for which the strain was chosen must be relatively stable. The CO2 produced throughout the fermentation is responsible for leavening or rising of the dough. The quality of the product based on the proper selection of yeast and the incubation conditions in addition to the choice of materials. The main unit operations comprised in baking is weighing, mixing, molding, fermentation, baking, cooling and packing.

Fermented Milks:

The greater part of fermented milk products mostly rely on the Lactic Acid Bacteria (LAB), fermented milks were generated for thousands of years before Louis Pasteur discovered lactic acid fermentation. LAB comprises species belonging to the genera lactobacillus, lactocococcus, Leuconostoc and streptococcus. Such bacteria are low G + C gram-positives which tolerate acidic conditions, are non-sporing and are aero tolerant having a strictly fermentative metabolism.

1) Cheese Production:

It is one of the oldest human foods. Cheese is categorized based on texture or hardness as soft cheese (that is, cottage, cream and brie) semi soft cheese (that is, Muenster, limburger and blue) hard cheese (that is, cheddar, Colby and swiss) or very hard cheese (that is, parmesan). All such outcome from a lactic acid fermentation of milk that yields in coagulation of the milk proteins and the formation of curd.

After the curd is prepared, it is heated and pressed to get rid of the watery part of the milk (termed as the whey), salted and then generally ripened. The cheese curd can be packed for ripening with or devoid of additional microorganisms. In certain cases, molds are employed to further improve cheese.

2) Probotics:

Microorganisms like Lactobacillus and Bifidobacterium are being employed in the fast developing region of Probotics, the advantage beyond basis nutritive value. Probotics is the oral administration of either living or substances to encourage health and growth consists of the potential to re-establish the natural balance and return the host normal health and nutrition.

3) Acidophilus milk:

This is produced through Lactobacillus acidophilus; L. acidophilus might modify the microbial flora in the lower intestine therefore enhancing general health. It is frequently in use as a dietary adjunct, particularly for lactose intolerant persons.

Meat and Fish:

Alongside the fermentation of dairy products, a diversity of meat products particularly sausage can be ferment. Country-cured hams, salami cervelat, summer sausage, fish sauces (processed through halophilic bacillus species) and so on. Izushi and katsuobusji Pediococcus cerevisiae and Lactobacillus plantarum are most frequently comprised in sausage fermentation.

Fermenters Design and Operation:

A fermenter is a vessel that doesn't permit contamination however gives conditions essential for the maximum production of the desired product. In designing and constructing a fermenter, a number of factors should be considered.

1) The vessel should be capable of being operated aseptically for a number of days and must be reliable in long term operations.

2) Sufficient aeration and agitation must be given to meet up the metabolic needs of microorganisms.

3) Power consumption must be as low as possible.

4) It should encompass a system of temperature control.

5) It should encompass a system of the pH control.

6) Sampling facilities must be given.

7) Evaporation losses from the fermenters must not be extreme.

8) The vessel must be designed to need the minimal use of labor in operation cleaning, harvesting and maintenance.

9) The vessel must be appropriate for a range of processes.

10) It must encompass smooth internal surface.

In a fermenter having strict aseptic requirement, it is significant to choose materials which can withstand repeated steam sterilization. On a small scale, glass stainless steel can be employed. Glass provides smooth surfaces; it is not toxic and corrosion-free. It is generally simple to observe the procedure while it is going on.

Temperature can be attained through placing a fermenter in a thermostatically controlled bath or by use of internal cooling coil via which cold water is circulated to attain the right temperature.

Scale Up Process of the Fermentation Process:

One of the most significant and complex feature of industrial microbiology is the transfer of a method from small scale laboratory equipment to big scale commercial equipment, a method termed as scale-up. In reality, a microbial method doesn't behave similar in large scale fermenters as small scale laboratory equipment. Therefore a proper comprehending of the problems of scale-up is extremely significant.

Mixing and aeration are much simpler to attain in the small laboratory flask than in the big industrial fermenters. As the size of the equipment is raised, the surface or volume ratio changes, the bigger antifoam agents.

  • Higher alcohol
  • Silicones
  • Natural esters
  • Lard and vegetable oils, palm oil
  • Fatty acids and derivatives
  • Castor oil

Fermenter consists of much volume for a given surface area. As gas transfer and mixing based more surfaces exposed than on fermenter volume. This is perceptibly harder to mix the big can than the small flask. Oxygen transfer is much harder to get in a large fermenter due to various surface or volume ratios. Most of the commercial fermentations are aerobic; therefore efficient O2 transfer is necessary.


Chemicals controlling foams have been categorized into antifoams or defoamers. Defoamers are once they are prepared. Most of the media employed in culturing organisms have protein that is susceptible to foam formation due to the fine bubble that simply induce foam. The problem of antifoam is prevalent in the fermentation method and can be counteracted in a number of manners. One possibility is to make sure that there:

Is an adequate space available in the fermenter for the foam generated. Though this decrease the efficient volume of the fermenters and also the additional modification of contamination. Foaming can as well be hindered or counteracted by employing chemical and mechanical measures.

Properties of Antifoams:

a) It should be non-toxic to microorganism and higher animals.

b) It should contain no effect on the taste and odor.

c) It should not serve as a source of the contamination.

d) It should not be metabolized (that is, organisms).  

Patents and Patent Law

A patent is a privileged granted through letter to an inventor to save a new invention. This is a form of protection issued through a government to an inventor of a latest product or methods who publicly disclose the details of his or her invention and in return is granted for the restricted period a legally enforceable right to leave out others from commercially exploiting it. Patent laws are set up for two reasons:

a) To induce the inventor to reveal something of his invention.

b) To make sure that an inventor is not exploited devoid of a certain reward to the invention for his innovations.

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