Part 8: Applied Microbiology Flashcards
Oldest evidence of cheese making
5500 BCE in Poland
Oldest winery
4100 BCE in Armenia
How long have we been using microbes for food preservation?
Since neolithic
Edible fungi
Mushrooms: fungal fruiting bodies
Agaricus bisporus
Edible fungi - button and protobellos
Edible algae
Seaweed
Red algae
Porphyra: Nori (sushi wrap)
Brown algae
Macrocystis (Alginate, a thickener)
Edible bacteria
Nucleic acid often too concentrated for food
Exception for edible bacteria
Cyanobacteria, Spirulina is used as a single-celled protein source and nutritional supplement
Fermented foods
Food products modified biochemically by microbial growth
Purposes of food fermentation
To preserve food: by limiting growth of spoilage organisms and also many pathogens
To improve digestibility: for example by breaking down lactose
To add nutrients (such as vitamins) and flavor (such as esters and sulfur compounds)
Indigenous flora
Found naturally in the food
Starter culture
From a previous fermentation
Homolactic acid fermentation
Yogurt, cheese
Propionic acid fermentation
Swiss cheese
Heterolactic acid fermentation
Kefir
Ethanolic fermentation
Wine, beer
Alkaline fermentation
Brie cheese
Milk fermentation begins by
Lactic acid fermentation with Lactobacillus and Streptococcus
Second step of milk fermentation
Rennet protelysis (by chymosin and pepsin), rendering casein insoluble
Cleaved peptides coagulate to form
Semisolid curd
Whey
Liquid portion of cheese production
Steps of cheese production
Milk is filtered and subjected to pasteurization
Fermenting microbes are added as a starter culture of different mixtures of bacteria for different cheeses
Drop in pH and/or added rennet (stomach proteases) help denature the milk protein called casein, which coagulates and precipitates out of solutions (curds)
Solid curd is cut
Curd is lightly heat-treated
Pressed curd is shaped into a mold
Cheese is ripened
Acidic fermentation food
Cabbage, cucumbers, olives, fermented meats
Pickling
Fermentation in brine (high salt)
High salt of brine selects for
Gram positive
Is a starter culture used in pickling?
It can be used or not
What selects against some pathogens in acidic fermentation?
Temperature
What organisms are used in acidic fermentation?
Pediococcus, Streptococcus, Lactobacillus, Leuconostoc
Initially what was used to rise bread
Natural mixture of wild yeasts and heterolactic acid bacteria
Most recent development of what is used to rise bread
Saccharomyces cerevisieae: Baker’s yeast
What fermentation does bread use?
Ethanolic
What causes bread to rise?
CO2
How is ethanol removed in bread?
By baking
What fermentation does beer use?
Ethanolic fermentation
What organism does beer use for fermentation?
Saccharomyces cerevisiae: Brewer’s yeast
Beer is derived from
Alcoholic fermentation of grain
Process of beer
Barley grains are germinated, allowing enzymes to break down the starch to maltose for yeast fermentation
Primary sugar fermented in beer
Maltose
Secondary product in beer
Long-chain alcohols and esters
What generates some of the special flavors of beer?
Alcohols and esters
What organism does wine use for fermentation?
Saccharomyces cerevisiae: Brewer’s yeast
What kind of fermentation does wine use?
Ethanolic
What does wine derive its alcohol fermentation from?
Fruit, usually grapes
Process of wine fermentation
Grapes are crushed to release juices
Yeast ferment sucrose, fructose, and glucose to ethanol
What is the difference between white and red wine?
Skin is removed
Malolactic fermentation is done through
Oenococcus oeni bacteria
Malolactic fermentation
Converts malate to lactate plus CO2 reducing the acidity
Fermentation of chocolate is done on
Piles of banana leaves
When is fermentation done in chocolate?
Prior to roasting of beans for flavor development
How are scientists trying to standardize the process of chocolate making?
They are trying to develop a defined starter culture in order to perform the fermentation in a controlled way
How does making chocolate start?
Complex series of natural fermentation
Why is it difficult to find a starter culture for chocolate?
Because the fermentation involves a succession of populations
Food spoilage
Refers to microbial changes that render a product obviously unfit or unpalatable for consumption
Acid taste
Sour
Rancidity
Oxidation of fats
Putrefaction
Decomposion of proteins
Alkalinity taste
Bitter
Food contamination or food poisoning refers to
Presence of pathogens
Dairy products are soured by
Excessive fermentation
Dairy products are made bitter by
Bacterial proteolysis
Meat and poultry are putrefied by
Decarboxyloating bacteria
What does decarboxylating bacteria produce?
Amines with noxious odors
Seafoods spoil rapidly because
Their unsaturated fatty acids rapidly oxidize (become rancid)
How does seafood get its fishy smell?
Psychotrophic bacteria reduce TMAO (trimethylamineoxide) to the fishy-smelling trimethylamine
Plant foods spoil by
Excess growth of bacteria and molds which can cause them to wilt, brown, and lose texture
Listeria monocytogenes
Psychrotrophic bacterium that invades the cells of intestinal epithelium
What environment does Listeria monocytogenes grow in?
Under refrigerated conditions
Physical means of preservation
Dehydration and lyophilization (freeze-drying) Controlled or modified atmosphere Pasteurization Canning Ionizing radiation Refrigeration and freezing
Chemical means of preservation
Organic acids
Esters
Other organic compounds
Inorganic compounds
Organic acids used for preservation
Benzoic acid, sorbic acid, and propionic acid
Esters used for preservation
Fatty acid esters and benzoic acid esters
Other organic compounds used for preservation
Cinnamon and mustard
Inorganic compound used for preservation
Salts such as phosphate, nitrates, and sulfites
Cinnamon as a preservative
Contains benzene derivative eugenol (a potent antimicrobial agent)
Mustard as a preservative
Contains sinalbin which can release isothiocyanate, which is toxic to bacteria
Industrial microbiology
Commercial exploitation of microbes
Industrial microbiology is the production of
Vaccines, pharmaceuticals, and therapeutics
Industrial solvents, biodegradable plastic
Genetically modified plant and animal cells
How many people have diabetes?
2.4 million Canadians
6.8% of population
1/11 Canadians over 20
Type 1 diabetes
5-10% of cases
Beta-islet cells are destroyed by immune system
Type 2 diabetes
90-95% of cases
Insulin receptors on cells desensitized to insulin
Insulin
Protein hormone produced by beta-islet cells (pancreas)
Who discovered the mechanism of diabetes?
Frederick Banting
When was insulin first produced and by who?
1921 by F. Banting and Charles Best
Where was the first insulin harvested from?
Animal (dog) pancreas
When did large-scale commercial production start?
1923 by Eli Lilly
What was the first large-scale commercial production made of?
Ground up bovine and swine pancreas gland
What happened when human were injected with bovine and porcine insulin?
Many patients formed antibodies against the foreign proteins
It caused inflammation and allergic response
What was the solution for bovine and porcine insulin?
Insert human insulin gene into E. coli to produce human insulin - recombinant DNA technology
Structure of insulin
51 amino acids
How many chains does insulin have?
2 chains - A and B chain
How many amino acids does each chain have?
A chain - 21
B chain - 30
What are the chains of insulin held together by?
Disulfide bridges
Manufacturing human insulin
DNA containing the A-chain genes and B-chain gene individual cloned into a plasmid vector
The recombinant plasmids DNA are then introduced into E. coli
Bacteria containing hte plasmid grown as large-scale cultures in fermenters
Become insulin factories that produce large amount of A-chain and B-chain polypeptide
Pancreatic cancer
Highly aggressive
Poor survival rate - less than 4% of people survive 5 years after diagnosis
“Silent killer” - cancer spreads before primary tumor detected
Symptoms of patients with metastasized cancer
Jaundice, pain, weight loss, and fatigue
What is the current treatment for pancreatic cancer?
Chemotherapeutic agents that improve median life expectancy for 6 months
What is a promising alternative therapy for pancreatic cancer?
Listeria monocytogenes
Mechanism of Listeria monocytogenes as treatment
L.m deliver anticancer radionuclides - targets and kills cancer skills
Anti-Listeria antibody linked to 188Re used to tag bacteria with deadly radioactivity
