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The word probiotics are extracted from the Greek “pribios” that means for life. In ancient time probiotics has been known to be present in fermented dairy products. Probiotics play a significant role in our lives since this field has been researched extensively over the past decades. The extensive researches conducted have shifted the focus on bacteria found in fermented dairy products to the bacteria found in the intestines. World Health Organization (WHO) states that probiotics are defined as live cultures of microorganisms since they are playing a significant role in the life of an animal. This is because they boost their indigenous microflora when eaten in huge amounts. According to Tannock, he states that the number of bacteria in and on the human body is over 1 billion cells which include parts such as the skin, oral cavity as well as the intestinal organs. Scientists state that probiotics bacteria have different health effects which include ameliorating stomach and intestinal organs functions, boosting immune roles, as well as lowering cancer cases (Priest and Goodfellow). The effective role of probiotics is to prevent diseases. Scientist’s state that probiotics can affect any part of the body and the bacteria can force our bodies to respond in a locally and systematically manner.
Some of the foods containing probiotics include yogurt, cheese, breakfast cereals, sausages, as well as infant formulas. For instance, yogurt is commonly consumed probiotics food in Bangladesh. The residents prefer foods containing effective bioactive characteristics, lactic acid bacteria (LAB) which contain massive amounts of probiotics and antimicrobial properties in relation to pathogenic microorganisms.
Probiotics
In the 21st century, the consumption of probiotics products in Bangladesh for both human and animals are on the rise. For instance, in Bangladesh, they have developed different probiotics products for animal consumption such as Bactosac, Probac, Poultry Star sol and Gutpro whereby they are rich in LAB species. Based on Frost and Sullivan analysis, European countries are focusing on the manufacturing of foods and beverages rich in probiotics which have improved the food industry in the region. However, Bangladesh manufactures probiotics for their animals and it is believed that dairy products such as yogurt and cheese are highly consumed in the region since they are rich in probiotics. This analysis shows that LAB probiotics can be used in different ways in the food and industries companies.
Lactic Acid Bacteria
Over the past years, lactic acid bacteria (LAB) have been used for fermentation and preservation purposes of foods. They are regarded to be generally recognized as safe (GRAS) by the FDA. This means that lactic acid bacteria can be used as part of food species. Scientists state that lactic acid bacteria is a diverse bacterial group made up of gram-positive, aerotolerant, acid tolerant, low GC content which is non-sporulating and non-respiring rod or cocci microorganisms (Kneifel and Salminen). These lactic acid bacteria groups can change lactose and other sugars to lactic acid. They are commonly found in milk and dairy products, raw meat, fermented products, and vegetables. The key components genera of LAB include Lactobacillus, Leuconostoc, Pediococcus, Lactococcus, Streptococcus, as well as Enterococcus. The minor components genera of LAB include Vagococcus, Weissella, Oenococcus, Lactosphaera, Aerococcus, and Bifidobacterium. These components constitute too high levels of bacteria that contain probiotics properties. Lactic acid bacteria can play a significant role in food and beverages industry since they contain high levels of probiotics nutrients. Lactic acid bacteria can prevent the damage of other microorganisms as well as the rise of pathogenic bacteria through its antimicrobial metabolic products such as organic acids and bacteriocin.
The consumption and use of lactic acid bacteria are on the rise due to the growth of antibiotic-resistant pathogens. There is a need to come up with a different method which will increase the use of antibiotics. For instance, Lactobacillus spp can help since it can grow in severe conditions as well as produce extracellular bacteriocin which can adapt to a different number of pathogenic strains. This means that lactic acid bacteria are effective in removing chemical elements and antibiotics because of their antimicrobial elements.
Antimicrobial Properties of LAB
The process of choosing probiotics is associated with the antimicrobial activity that they provide. Lactic acid bacteria provides antimicrobial effects through different elements such as lactic acid, acetic acid, propionic acids, carbon dioxide, hydrogen peroxide, diacetyl, bacteriocins as well as low molecular weight substances. According to Collins, La Ragione, Woodward and Searle have stated that antimicrobial compounds of lactic acid bacteria can be classified into two different groups such as low molecular mass substances (<1000 Da) and high molecular substances (>1000 Da). High molecular elements are defined as bacteriocins. The other antimicrobial elements are classified under low molecular mass compounds which include organic acids, diacetyl, hydrogen peroxide, as well as carbon dioxide (Sonomoto and Yokota). These acids and the level of their acid products are important during the fermentation because of the microbial activity associated with fermented substances and can cause toxic effects on other microbes. The operations of the main molecular mass substances include One, organic acids which grow as a result of sugar conversion and important in preservation since they reduce pH. Lactic acid and Acetic Acid are the best organic acids of LAB. The levels of these acids are important since they boost the antimicrobial effect in the fermented products. Two, carbon dioxide plays a significant role in preserving food. This is because it provides an anaerobic surrounding that removes the available molecular oxygen. Also, it provides antifungal activity since it has enzymatic decarboxylations and hinders it from growing in the lipid bilayer membrane that leads to permeability malfunction. Three, hydrogen peroxide is considered as a high antimicrobial because of its strong oxidizing effect on bacterial cells. This is because of its breaks down the basic molecular structure of cell proteins. Four, 2,3-butanedione, diacetyl is preferred for its buttery scent it provides to fermented dairy products. High levels of diacetyl are required for food preservation.
Bacteriocins
They are defined as bioactive proteins and peptides with high molecular mass which has been synthesized ribosomally. Bacteriocins can either be bacteriostatic or bactericidal, thus means that they either have the characteristics of pathogenic microbes or they destroy pathogenic microbe. Regardless of the method used, it will not affect the producer cell. The release of bacteriocins by the lactic acid bacteria cells is associated with different physical factors such as temperature, pH, as well as the source of nutrients. Also, bacteriocin release is considered to be high at the end of the log phase and the beginning of the stationary phase during cell growth.
Bacteriocins are believed to have a tick spectrum in relation to other bacteria compared to antibiotics. Also, bacteriocin can function with different metabolic products of LAB such as organic acids (Reeves). However, LAB bacteriocins function against other bacteria by destroying cell membranes and scattering the proton motive force. Gram-negative bacteria are not affected by these attacks since their external membrane provides cover for them. Bacteriocins are believed to have antimicrobial activity in relation to gram-positive bacteria which are related species and food spoilage and pathogenic bacteria such as Bacillus cereus, Staphylococcus aureus, as well as Listeria monocytogenes.
Probiotic bacteria are able to adapt to the growth of pathogenic strains since they fight for nutrients and attachment sites on the colonic epithelium and also produce organic acids and bacteriocins. However, if the LAB tends to have antagonistic effects on pathogenic species, this approach will show their effectiveness because of the large volume of diseases arise due to foods containing bacterial growth.
Materials and Methods
The research was conducted in the Biotechnology and Microbiology, Department of Mathematics and Natural Sciences, BRAC University. Lactic acid bacteria were extracted from vegetables, fruits dairy, as well as herbs and there, were 35 samples in total.
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