Lecture 4 Flashcards
What is the cross-streak method used for?
To test new microbial isolates for antibiotic production
Process of testing activity spectrum?
-Streak antibiotic producer across one side of plate
-Incubate to permit growth and antibiotic production- antibiotic diffuses into agar
-Cross streak with test organisms
-Incubate to permit test organisms to grow - growth of test organisms - inhibiion zones where sensituve test organisms did not grow
What are marine bacteria asource of?
Novel antibiotics
Antiobiotic assays - agar diffusion assay mo?
Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Clostridium difficile
Saccharomyces cerevisiae, candida glabrata, candida albicans, aspergillus fumigatus
What are Penicillins and what is its production?
-Penicillins are ß-lactam antibiotics
-Natural and biosynthetic penicillins, semisynthetic penicillins-broad spectrum of activity
-Penicillin production is of a secondary metabolite
-Production begins after near exhaustion of the carbon source
What represses penicillin production?
High levels of glucose
What is penicillin usually fermented with?
Penicillium chrysogenum
How are antibiotcs that end in -cillin been made?
Add a beta lactam ring to it
- Thiazolidine ring
- ß-lactam ring
R1-acyl side chain
What are exoenzymes?
Enzymes that are excreted into the medium instead of being held within the cell - they are extracellular
-Can digest insoluble polymers such as cellulose, protein and starch
Why are enzymes useful sas industrial catalysts?
Only produce one stereoisomer
High substrate specificity
What are enzymes produced from - give an example?
Produced from fungi and bacteria
-bacterial proteases are used in laundry detergents (can also contain amylases, lipases and reductases) - isolated from alkaliphilic bacteria
-Amylases and glucoamylases are also commercially important as produce high fructose syrup
What are extremozymes?
-Enzymes that function at some environmental extreme -pH or temp
-Produced by extremophiles
What organism did the enzyme used to amplify DNA in PCR come from?
Thermophilic organism - Thermus aquaticus Taq Polymerase
-Active at 95 degrees
Look at microbial enzymes and their applications table
What kind of extremozyme is pullulanase?
Thermophile with optimal growth temp of 100 degrees
At 110 degrees C the enzyme denatures, but calcium improves the heat stability
Catalyses the conversion of starch to oligosaccharides
What are immobilised enzymes?
Immobilised enzymes are attacged to a solid surface
-Used in the starch processing industry
What are the 3 ways to immobilise an enzyme?
-Bonding of enzyme to a carrier
-Cross-linking of enzyme to molecules
-Enzyme inclusion e.g in microcapsules
Why are enzymes immobilised?
So that they can be reused to save money - products can be continuously made - Continuous Flow Processing
Used in the production of lactose free milk and inglucose testing strips to measure glucose levels in diabetics
What is brewing and what are the 2 main types of brewery yeast strains?
Brewing describes the manufacture of alcoholic beverages from amlted grains
-Yeast is used to produce beer
-2 main types of brewery yeast strains are i)Top fermenting - ales ii)Bottom fermenting - lagers
What happens in fermentation?
Yeast converts sugars in the wort (liquid extracted from the mashing of barley) to ethyl alcohol and CO2
What must yeast strains do in fermentation?
-Produce an active fermentation in wort
-Form aggregates easily at the end of fermentation
-Produce volatile acids and higher alcohols that contribute to flacour and aroma
What is an example of a top fermenting strand and how does fermentation take place?
Saccharomyces cerevisiae
-Rise to top with CO2
-Used in ale production
-Fermentation takes at 15-20 degrees and takes 5-7 days
What are examples of bottom fermenting yeast strains and how does fermentation take place?
S.uvarum, S.carlsbergensis
-Tend to fall to the bottom during fermentation
-Used in lagers
-Fermentation kept at 5-15 degrees and takes 12-14 days.
What are lagers stored at and why is this?
Largers are stored at 0-3 degrees for up to 4-6 weeks to permit a slow secondary fermentation to take place - process called lagering
What happens the beer after the lagering process?
The beer is filtered using filter aids resulting in the removal of yeast cells and protein complexes
The beer is then saturated with CO2 under pressure, pasteurised and distributed in kegs or bottles
Wwhat kind of microbes are brewers yeast strains?
Faculative anaerobes - can grow in presence or absence of O2
Yeasts in glycolysis?
Yeasts ‘detoxify’ the pyruvate by converting it to Ethanol while at the same time regenerating NAD+ which is consumed during glycolysis
What is the Crabtree effect?
The use of fermentation in the presence of oxygen and at high glucose concentrations - used by S.cerevisiae
What is respiration repressed at?
0.4% glucose - during a typical brewery fermentation, wort contains 1% glucose so respiration is repressed
