Bacteria And Fungi Involved In Yogurt Production

Project and Seminar Material for Science Laboratory Technology SLT

Bacteria And Fungi Involved In Yogurt Production


Yogurt sold at different manufacturer, in Ilorin Kwara State was taken to the laboratory and examined, different bacteria and fungi were found in all the yoghurt tested using conventional methods. The implications of these micro organisms were discussed.

Table of Contents

  • Title page
  • Certification
  • Dedication
  • Acknowledgements
  • Table of contents
  • List of tables
  • List of figures
  • Abstract

Chapter One

  • 1.0 Introduction and Literature Review

Chapter Two

  • 2.0 Materials and Method
  • 2.1 Sterilization of apparatus
  • 2.2 Collection of samples
  • 2.3 Preparation of culture media
  • 2.3.1 Nutrient agar (NA)
  • 2.3.2 Potato dextrose agar (PDA)
  • 2.4 Preparation serial dilution
  • 2.4.1 Serial dilution for nutrient agar
  • 2.4.2 Serial dilution for potato dextrose agar
  • 2.5 Bacteria examination and isolation
  • 2.6 Fungi examination and isolation
  • 2.7 gram staining
  • 2.8 Catalyses test

Chapter Three

  • 3.0 Results
  • 3.1 Colonial morphology and biochemical characteristics of bacteria isolate
  • 3.2 Colonial morphology of fungal isolates
  • 3.3 Description and identification of fungi isolates

Chapter Four

  • 4.0 Discussion
  • 4.1 Conclusion
  • 4.2 Recommendation
  • References

List of Table

  • Table 1: Colonial morphology of bacterial Isolates
  • Table 2: Colonial morphology of fungal Isolates
  • Table 3: Total colony count of bacteria lml (CFU)
  • Table 3B: Total colony count of fungi lml (CFU)
  • Table 4A: Distributions of bacterial isolates among sample
  • Table 4B: Distributions of fungi isolates among sample
  • Table 5A: Characterizations of bacterial Isolates
  • Table 5B: Characterizations of fungi Isolates

List of Figure

  • Figure 1: Rhizopus
  • Figure 2: Aspergillus niger
  • Figure 3: Saccharonyces

Chapter One

Introduction and Literature Review

Yogurt is a popular and healthy snacks and it has a lot of advantages over fresh milk despite the fact that yogurt is also a bye product of milk. The advantages it has over milk includes

  1. It can’t get perish like milk which get soured when it is not in refrigerator.
  2. It is thicker than milk which makes it easier to store and broadens it cooking.
  3. It gives a lot tangy flavour that people find appealing
  4. It also contain low lactose unlike milk that has high lactose which makes it to be easily digestible for some people that has low lactose tolerance.

The bacterial that helps in converting milk into this yogurt are

(a) Bacterial which are of two strains


Along with bacteria fungi also take part in the formation of yogurt production. These micro organisms were mistakenly added to milk along with a plant like bacteria LACTOBACILLIUS BULGARICUS which is related to the strain of plant dwelling bacteria.

In the process of adding more LACTOBACILLIUS BULGARICUS into the milk produce more yogurt. it was now noted that STREPTOCOCCUS THERMOPHILLIUS has same symbiotic relationship with LACTOBACILLIUS BULGARIUM.
Yogurt is form through the conversion of lactose to lactic acid by LACTOBACILLIUS BULGARIUM so yogurt are made acidic through this process and also makes the milk’s protein thicken and thereby making it viscous. The acidity also prevents colonization from other microbes which aids in preservation.

By breaking down lactose to make the lactic acid the microbes lower the levels of lactose in the yogurt while the presence of STREPTOCOCCUS THERMOPHILLIUS helps to fight along with LACTOBACILLIUS BULGARIUM against any microbes from outside during the early stage of the process .
Originally a simple fermented diary product, yogurt now has many variations and personalities. It can be thin and runny or thick and firm. It can be made from cow milk, goat milk, sheep milk, nut milk, soy milk, rice milk and from numerous other creamy substances.

In some countries the milk of buffalo, horse, yorks or camels is used for most of this discussion, we refer to yogurt in its originally form for fermented dairy milk. This was how yogurt was first developed, and most of the yogurt in the world is made this way. Essential yogurt is the product of beneficial bacteria fermenting milk and turning it into a thickened, acidic food that will stay fresh longer than milk itself, and that contains millions of bacteria that are welcomed by the human gut.

The word yogurt comes from Turkish word meaning to curdle or to thicken. Its probable that the earliest yogurt was made by accident in Mesopotamia around 5,000 BC, when milk producing animal were first domesticated. The milk was, likely stored and transported in bags made from the stomach of these animals, and the digestive juice and bacteria in the stomach livings made the milk coagulated and become acidic. Not only was it a new and interesting food, but the acidity helped to keep it edible for longer than if it had just sat out in a bowl or jar, the acidity of the yogurt helps clean away dirty and rust and also helps clear away dead skin and nourish healthy skin cells. Yogurt was a popular food in the Middle East for thousands of years and has been a staple of the eastern European diet. Its now eaten throughout the world, as a main course, a snack, an ingredient in many recipes and a condiment. It has a gained considerable popularity in America in the last forty or fifty years. Yogurt can be mildly tart or quite sour, and can be thick enough to stand up on a plate, or thin enough to pour or anywhere in between. It contain protein and calcium as well as variety of vitamins. Additionally, the process of yogurt fermentation is very similar to the process of digestion, so it can be easily consumed.

Not only does yogurt contain the same amount of protein and fat as the milk from which it is made, it also contain calcium, riboflavin, vitamin B6, and vitaminB12 while numerous claims have been made regarding the health benefits and digestibility of yogurt.

Hahai (2009)reported that a new type of yogurt prevent gastrointestinal distress; A new yogurt, containing urea’s antibodies, as been shown to prevent helicobacter pylori from binding to stomach walls and causing infection such as gastritis and stomach ulcers. This yogurt is made using vaccine-making technology urea injected into chickens allowed their immune system to produce an antibody to increase called igy-urease. The antibody is then harvested from chickens eggs and made into yogurt containing lactobacillus acidophilus, Bifid bacterium and egg yolk igy-urease. This yogurt is particularly significant in developing countries where standard of care treatment like antacid and antibiotics are either unavailable or unaffordable it is currently available in Japan, Korea, and Tawan, Fleet G.,(1990).

The aim and objectives of this project work, apart from the academic on our part by the independent, is to make the public know different types of microorganism that takes part in yogurt production, to put the mind of the public at rest that not all microorganisms are harmful to human, to give the types, roles, effect and importance of these micro-organisms that involve in the production of yogurt and to produce good personelles.

Chapter Four

4.0 Discussion

From the studies carried out a total of five bacteria and three fungi were isolated. The tree samples of yoghurt collected from different areas were subjected to series of test. During the period of investigation, the colonial morphology and biochemical characteristics of bacteria shows the characteristics of the bacteria and their names were suggested (Tag III) the result also correspond to the detected at Onitsha. The suggested bacterial are shaphylococcus that has round shaop, yellow colour, raised eleration, opaque, gram positive and its catalase test is positive. Escherichia coli has a round shape, cream colour, raised elevation trans lucent, gram negative and catalase position Bacillus has rod shape, cream colour, Raise elevation opaque gram position and cartelise position lactobacillus has round shape, white colour, flattened elevation, opaque, gram position and the catalase test is negative. Streptococcus has round shape, cream colour, flattered elevation opaque, gram position and catalase test negative. All tese results correspond with those gotten at Onisa according to (Table 1).

According to Predigon, 1995, the study of the microflora of the yogurts in Onitsha gives isolation of streptococcus and Lactobaciltus spp which we agreed because it was part of what we do discovered on because it was part of what we discovered during our experiment. According to him these two microorganism are the most functional organisms in the fermentation of Yoghurt.

The fungi detected were just three from the comparison between (Tab II) and (Table IV) we believed that the characteristics of the fungi detected are almost the same. The colonial morphology of fungal isolates are for rhizoplus spp the colony morphology shows that it has black fluffy with green coluration with powdery appearance. Microscopic characterization shows that it is non – septite hyphase with sporangropore and rhizoids.

Saccharomyces spp has a cream colour circulate with a blackish surface at the center. The microscopic characterization shows that it is spherical or oral in shape. Aspergittus Niger has a pate green colour with a rough surface, its microscope characterization shows that these map like condispores. All this characters help us to identity these microorganism and since we are not really sure we said they are likely microorganism until further test is conduction it.

According to (Trema, 1998) presence of Saccaromyces spp are responsible for flavour and aroma and it involves in fermentation. The isolation of Aspergillus Niger and Rhizopus spp agreed with what (Oyeleke, 2009) said that moulds and bacillus were the main contaminants in yoghurt.

Conclusion and Recommendation

Yogurt is a popular and healthy snacks and it has a-lot of advantages over fresh milk. It gives a-lot of tangy flavour that people find appealing and also contain low lactose unlike milk that has high lactose which makes it to be easily digestible for some people that has low lactose tolerance (Gallagher, C.R 1999.). Yogurt is also a product or bye product of milk. I recorded that yogurt is good.

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