MCB 11 Lab Exer9

• Fermented Vegetable


  1. Dry-salting or brining the vegetables

  2. Natural microbiota of the vegetable is used to carry out the process

  3. Sugars are converted to lactic acid giving the finished product new characteristics
• Significance of salting


  • Imparts desirable flavor to the product
  • Helps maintain a crisp texture by inhibiting pectinolytic enzymes responsible for tissue softening
  • Facilitates diffusion of sugars and other nutrients due to osmosis
  • Provides a selective condition that will discourage the growth of non-LAB
  • Gives a substantial growth advantage to the LAB due to their relatively higher salt tolerance
• Burong mustasa


  1. Addition of boiled rice water

  2. Anaerobic environment
• Addition of boiled rice water

  Increases the dissolved carbohydrates in the starting material, which will be later converted to lactic acid
• Anaerobic environment


  • Covering the jar with plastic + putting water weight on top – physical exclusion
  • Residual respiration and oxygen consumption by plant cells reduces the redox potentials inside the jar
• Growth of LAB


  1. Favored by the addition of salt and the anaerobic environment inside the jar

  2. Production of lactic acid lowers the pH inhibiting non-LAB competitors

  3. May be accompanied by the production CO2 which further contributes to the anaerobic environment
• Growth succession of microorganisms

  1. Fermentation that occurs does not depend on a single organism, but rather a consortium of bacteria representing several genera and species growing in succession

  2. A given organism (or group of organisms) will initiate growth and become established for a certain time

  3. The growth of the initial group will begin to slow down or stop upon accumulation of acid end products and other inhibitory factor

  4. The initial microbial population will give way to other species that are less sensitive to the inhibitory factors and so on
• Lactic Acid Bacteria


  • Enumeration on de Man, Rogosa, and Sharpe (MRS) agar
  • Canister with candle - the flame inside the container will use up the available oxygen until it dies down. Along with the physical exclusion of oxygen by putting a lid, this will provide the growth conditions for the aerotolerant anaerobe LAB.
• Coliforms


  • Bacteria present in the environment and in the feces of all warm-blooded animals and humans. Their presence indicates that pathogenic microorganisms could also be present in the food and water.
  • Enumeration on Violet Red Bile Agar
• Vinegar


  • A solution containing at least 4% acetic acid
  • Produced from the acetous fermentation of ethanol
  • pH between 2.0 and 3.5
  • Contains small amounts of alcohol, glycerin, esters, sugars, and salts
  • Result of two distinct processes: ethanolic fermentation performed by yeasts and production of acetic acid from ethanol by acetic acid bacteria
• Preparation of Yeast Starter Culture

  1. Increase the number of yeast cells that will initiate the fermentation

  2. Shaking – aeration; dissimilation of one molecule of glucose under aerobic conditions results to more ATP molecules, and hence faster growth but only up to some extent