ch 29 & 30 self review

What kinds of microbes are consumed as food? Why are most bacteria inedible for humans?

Microbes consumed as food include bacteria (e.g., Cyanobacteria Spirulina), algae, mycelium, and yeast. Most bacteria are inedible because they contain high levels of nucleic acids (DNA and RNA). The human digestive system converts these purines to uric acid, which can cause gout and kidney stones if consumed in large quantities.

What are the advantages of fermentation for a food product?

• Advantages: Fermentation preserves food, improves digestibility, and adds nutrients and flavors.

Define traditional fermented foods?

These are homemade products made using methods thousands of years old.

What are the major chemical conversion that occur in fermented foods?

• Acid fermentation: Generates organic acids (lactate, propionate), lowering the food's pH.

• Alkaline fermentation: Produces ammonia, which increases the pH.

• Ethanolic fermentation: Produces ethanol and carbon dioxide.

Briefly describe the process and microbial groups in the production of fermented milk product, beer, wine, chocolate, bread leavening.

• Fermented Milk: Relies on lactic acid bacteria (e.g., Lactobacillus, Streptococcus); milk is treated with these bacteria and rennin to form curd, which is then ripened into cheese or yogurt.

• Beer: Grain is malted and mashed to release sugars, then fermented by Saccharomyces yeast to produce alcohol and flavor compounds.

• Wine: Grape sugar is fermented to alcohol by Saccharomyces cerevisiae, often followed by malolactic fermentation using Oenococcus oeni to convert malic acid to lactic acid.

• Bread Leavening: Ethanolic fermentation by Saccharomyces cerevisiae produces CO₂, which expands the dough to create a network of air pockets.

• Chocolate: Requires a complex succession of microorganisms in the fruit pulp.

Describe briefly about the three stages microbial succession during cocoa bean fermentation.

1. Yeast (Anaerobic): Degrade pectin and ferment sugars and citric acid into ethanol, CO₂, and acetate, which increases the pH.

2. Lactic Acid Bacteria (Anaerobic): Convert sugars into lactic acid, acetate, and CO₂.

3. Acetic Acid Bacteria (Aerobic): Once beans are turned and mixed with oxygen, Acetobacter oxidizes ethanol to CO₂ and causes polyphenol oxidation, which provides the brown color and flavor.

Define food spoilage, food contamination, food intoxication with examples.

• Food Spoilage: Microbial changes that make a product unpalatable or unfit for consumption.

• Food Contamination: The presence of microbial pathogens that cause disease.

• Food Intoxication: Disease caused by ingesting toxins already present in food (e.g., botulism or staphylococcal poisoning), where the growth of the microbe inside the host is not required for symptoms.

What are the top 5 germs causing illness, hospitalization, and deaths from food eaten in the United States?

• Illness: Norovirus, Salmonella, Clostridium perfringens, Campylobacter, and Staphylococcus aureus.

• Hospitalization: Salmonella, Norovirus, Campylobacter, Toxoplasma gondii, and E. coli O157.

• Death: Salmonella, Toxoplasma gondii, Listeria monocytogenes, Norovirus, and Campylobacter.

What are common detection methods for food-borne pathogens?

• Detection Methods: Culture techniques (slow but reliable), immunological techniques (sensitive), and molecular techniques like PCR and whole-genome sequencing.

What are the methods for food preservation and food sterilization?

• Preservation Methods: Filtration, dehydration, refrigeration, acid treatment, pasteurization, chemical preservatives, and radiation.

• Sterilization Methods: Canning (pressure cooking to destroy endospores) and ionizing radiation (food irradiation).

Define industrial microbiology. What are some industrial products using microbial systems?

• Industrial Microbiology: Large-scale use of microorganisms to synthesize commercial products like antibiotics, vaccines, and biofuels.

Define bioprospecting. Why extremophiles are important sources for source strains?

• Bioprospecting: Screening new microbial strains from nature for promising traits. Extremophiles are important because their enzymes may be active at high temperatures or across a wide range of conditions.

What is the difference between source strain and industrial strain?

• Source vs. Industrial Strain: A source strain is the original organism with the desired genes, while an industrial strain is a well-studied species (like E. coli) optimized for growth into which those genes are cloned.

What are the characteristics of industrial strains?

• Industrial Strain Characteristics: Genetic stability, inexpensive growth needs, safety (nonpathogenic), high product expression, and ease of harvesting.

Define upstream and downstream processing in industrial microbiology.

• Processing: Upstream processing involves culturing the microbe to produce product mass; downstream processing involves product recovery and purification.

Give examples of microbes as product.

• Microbes as Products: Examples include bacterial insecticides (Bacillus thuringiensis) and biological fungicides (Streptomyces lydicus).

What is subunit vaccine? What part (gene) of SARS-CoV-2 virus is used to produce mRNA vaccine against it?

• Vaccines: A subunit vaccine includes only specific parts of a pathogen to stimulate immunity. The mRNA vaccine for SARS-CoV-2 uses the gene encoding the spike protein.

Describe briefly about the use of microorganism during insulin production.

• Insulin: Human insulin genes are cloned into a heterologous host like Escherichia coli or Saccharomyces cerevisiae using genetic engineering for mass production.

What are the area for microbial usage in industrial and environmental microbiology?

Microorganisms are also used in biofuel production, microbial fuel cells, wastewater treatment, biodegradation, bioremediation, and metal bioleaching.