Booklet 8: Food and Industrial Microbiology Flashcards
Give some examples of microbes as food
Edible fungi - mushrooms (fungal fruiting bodies)
Edible algae - seaweed (Porphyra/Nori)
Edible bacteria - cyanobacterium spirulina is used as a single celled protein source and nutritional supplement
List 3 purposes of food fermentation
To preserve food (limit growth of bacteria capable of spoilage)
To improve digestibility (breaking down lactose)
To add nutrients and flavour molecules
What 2 things do fermented foods usually depend on?
indigenous flora
starter cultures
Define indigenous flora
Found naturally in the food
Define a starter culture
From a previous fermentation
List 5 things that major classes of fermentation include
Homolactic acid fermentation (yogurt,cheese)
Propionic acid fermentation (swiss cheese)
Heterolactic acid fermentation (kefir)
Ethanol fermentation (wine, beer)
Alkaline fermentation (brie cheese)
Describe milk fermentation
Begins by lactic acid fermentation with Lactobacillus and Streptococcus. This is followed by rennet proteolysis (by chymosin and pepsin), rendering casein insoluble. The cleaved peptides coagulate to form a semisolid curd. Separated from the liquid portion called whey.
Describe cheese production
- Milk is filtered and subjected to pasteurization.
- Fermenting microbes are added as a starter culture
- Drop in pH and/ or added rennet (stomach proteases) help denature the milk protein called casein which coagulates and precipitates out of the solution as curds.
- The curd is then cut
- Curd is lightly heat-treated
- Curd is shaped into a cold
- Curd is ripened or aged
Define acidic fermentations
Also known as pickling. Examples include cabbage, cucumbers, olives, fermented meats.
Describe the process of pickling (fermentation in brine - which is a high salt environment)
- High salt selects for specific bacteria(Gram positive)
- Starter cultures may be used
- Room temp/cold temp is selective against certain pathogens
List some bacteria used in acidic fermentation
Pediococcus, Streptococcus, Lactobacillus, and Leuconostoc
What are some the most popular examples of ethanol fermentation?
Making of bread, beer, or wine
Describe the process of bread making.
Initially bread was allowed to rise using a natural mixture of wild yeasts and heterolactic acid bacteria (sourdough).
More recent development is known as baker’s yeast (Saccharomyces cerevisiae)
Pyruvate is converted to ethanol and CO2.
CO2 is a gas and expands and the bread which causes it to rise.
Describe the process of making beer.
Also uses Saccharomyces cerevisiae
This time this bacteria is referred to as Brewer’s yeast.
Beer derives from alcoholic fermentation of grain.
Barley grains are germinated, allowing enzymes to break down the starch to maltose for yeast fermentation.
So maltose is the primary sugar fermented
Secondary products include long chain alcohols and esters generate some of the more specific flavours of beer
Describe the process of making wine
Also uses Brewer’s yeast (Saccharomyces cerevisiae)
Wine derives from alcoholic fermentation of fruit, usually grapes.
The grapes are crushed, and for white wine, the skin of the grapes is removed, for red wine, the skin stays on.
The yeast ferments sucrose, fructose, and glucose to ethanol.
Red wine and some whites undergo malolactic fermentation by Oenococcus omni bacteria which converts malate to lactate plus CO2 reducing the acidity.
How is the making of chocolate started?
Starts with a complex series of natural fermentations.
What refers to a microbial change that renders a product obviously unfit or unpalatable for consumption?
Food spoilage
Describe 4 kinds of food spoilage and the undesired effect that is present due to the food spoilage.
Acids - sour taste
Oxidation of fats - rancidity
Decomposition of proteins - putrefaction
Alkalinity - bitter taste
When is food spoilage considered food contamination or food poisoning?
When pathogens are present
Describe the food spoilage of dairy products
Dairy products can be soured by excessive fermentation or made bitter by bacterial proteolysis.
When dairy products are spoiled they usually have a distinct unpleasant odor associated with them.
Describe the food spoilage of meat and poultry
Meat and poultry are putrefied by decarboxylating bacteria, which produce amines with noxious doors.
Why do seafoods spoil so rapidly?
Seafoods spoil rapidly because their unsaturated fatty acids rapidly oxidize (become rancid).
Psychotropic bacteria reduce trimethylamineoxide to the fishy-smelling trimethylamine.
Describe the foods spoilage of plant foods
Plant foods spoil by excess growth of bacteria and holds, which can cause them to wilt, brown, or else lose their texture.
What does the psychotropic bacterium, Listeria monocytogenes, cause? (This is the bacteria that is commonly found on luncheon meats)
This bacteria causes listeriosis. This is such a big problem because these bacteria can still grow under refrigerated conditions.
Why is listeriosis such a concern for pregnant women?
Can cause spontaneous abortion
List some physical means of food preservation.
- Dehydration
- Freeze drying (lyophilization)
- Controlled or modified atmosphere
- Pasteurization
- Canning
- Ionizing radiation
- Refrigeration
- Freezing
What is the difference between bacteria cidal and bacteria static ?
Bacteria cidal kills the bacteria while bacteria static just stops the bacteria from growing and/or reproducing.
List some chemical means of food preservation
- Organic acids - benzoic, scorbutic, or propionic acid
- Esters - fatty acid esters or benzoic acid esters
- Other organic compounds - cinnamon contains a benzene derivative eugenol which is an antimicrobial agent, and mustard contains sinalbin which can release isothiocyanate, which is toxic to bacteria
- Inorganic compounds - salts, nitrates, sulphates
What is industrial microbiology?
The commercial exploitation of microbes
What does industrial microbiology include?
Mainly food production and food preservation.
Also includes production of vaccines, pharmaceuticals, therapeutics, industrial solvents, biodegradable plastics, and genetically modified plant and animal cells.
Describe the disease Diabetes
Two types: Type 1 and Type 2
Type 1 - approx 10% of cases
Type 2 - approx 90% of cases
Type 1: B-islet cells are destroyed by your immune system
Type 2: Insulin receipts on cells desensitized to insulin
Which type of diabetes is usually associated with obesity?
Type 2
What is insulin?
A protein hormone that is produced by the B-islet cells in the pancreas.
True or False: The first manufactured insulin came from animals
True
Why did we discontinue using animal insulin to manage human diabetes?
- Many patients formed antibodies against the foreign protein.
- It caused allergic responses and inflammation in some patients.
- The long term affects were not known
What was produced instead of continuing to use animal insulin?
The human insulin gene was inserted into E. coli.
We produced human insulin through a recombinant DNA technology.
Describe the structure of insulin
It is a protein hormone. 51 amino acids Two chains: A chain - 21 amino acids B chain - 30 amino acids The A and B chains are held together by disulfide bridges.
List the 4 components of manufacturing human insulin.
Foreign DNA
Sticky ends
Vector
Cloned DNA
List the actual process of manufacturing human insulin
- DNA containing the A chain and B chain gene are individually cloned into a plasmid vector
- The recombinant plasmids DNA are then introduced into E. coli
- Bacteria containing the plasmid grown as large-scale cultures in fermenters
- Become insulin factories that produce large amounts of A chain and B chain polypeptide
T or F: making human insulin results in a 100% pure synthetic version of human insulin
True
What can radioactive bacteria reduce?
The spread of pancreatic cancer
List some points about pancreatic cancer
- highly aggressive
- poor survival rate
- “silent killer” because it usually spreads before the primary tumor is discovered
- patients with metastasized cancer usually have symptoms such as: jaundice, weight loss, or fatigue
- urgent need for alternative therapies
What is an alternative therapy for pancreatic cancer?
Listeria monocytogenes
-A weakened lab form of L.m. can infect the cancer cells and not harm the healthy cells
Describe how a weakened lab form of L. monocytogenes can infect the cancer cells and not harm the healthy cells
- In normal tissue, the immune system would clear the bacteria
- In an immunosuppressed region such a tutor region - bacteria are able to enter the tissue and kill the cells
- L.m delivers anticancer radionuclides and targets and kills the cancer cells
T or F: Listeria monocytogenes multiplies quite rapidly in both primary tumor and normal tissue
False: only in primary tutors, not in the normal tissues
What element is anti-Listeria antibody linked to?
Rhenium 188
Why does L.m. affect the mestastic tissue the most and not the healthy tissue?
- Radiation induces irreplaceable DNA damage in fast-growing (metastatic) cells
- Normal tissue is generally not dividing
What is a brief summary of the L.m. and tumor growth?
live attenuated bacteria can deliver radioactivity to pancreatic cancer metastases without severe side effects
