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definitions flashcard exam IV

definitions flashcard exam IV - 3.fed-batch...

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2/10/11 1. batch process or fermentation : is when you throw in all the nutrients that the cell needs in excess while shutting off everything. You do not intervene during the process and then the process is done. 2. Corn Steep Liquor : complex nitrogen source under certain growth condition for certain bacteria (i.e. Lactobacillus delbrueckii ) 3. fed-batch process/fermentation : might start with a little bit of batch processes to get the cells growing. Then you fed in one or more nutrients with time and the vol. changes. By doing this, you’re able to control the nutrient level very well… 1) Osmotic stress for microbial cells is reduced. 2) Substrate inhibition is avoided. 3) Cell growth can be limited by any nutrient desired. 4) Nutrient limitation prevents oxygen demand from exceeding capacity of bioreactor. 4. productivity of a fermentation: introduced the notion of rate. How fast/quickly are the organism producing the products. 5. lactic acid bacteria (LABs): • Phylogenetically related organisms which naturally accumulate significant quantity of lactic acid • Generally, biosynthetic capacity is “underdeveloped” • Gram-positive, non-sporulating, non- motile, aerobic to facultatively anaerobic, lack cytochromes • Used as starter cultures in dairy products (yogurt, buttermilk, cottage cheese,…) • Used in processing/preservation of diverse foods (cured hams, pickles, sauerkraut, beer) 6. homofermentative LABs: • Produce (theor. max) 2 moles lactate per mole hexose • Possess aldolase (enzyme) • Those homofermenters that can consume pentoses do so heterofermentatively • Generate more ATP, but more acid - less flexibility 7. heterofermentive LABs : • Produce (theor. max) 1 mole lactate per mole glucose • Produce other substances (e.g., diacetyl) • Possess phosphoketolase (enzyme) (use pentose phosphate pathway also the one produces CO2) • Generally able to ferment a wide range of pentoses • Generate less ATP, but less acid - more flexibility 8. nisin: “group N inhibitory substance” 34 amino acid, positively charged peptide Produced by Lactococcus Improves shelf-life of numerous foods Interacts with a docking molecule, lipid II, a membrane- bound precursor for cell wall biosynthesis to form pores. Causes “leaky cells”. prevents endospore germination effective inhibitor at nM concentrations against numerous pathogens ( Clostridium , Listeria ) 10. volumetric productivity :
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2/10/11 13. PCB: a family of highly toxic chemical compounds consisting of two benzene rings in which chlorine takes the place of two or more hydrogen atoms: known to cause skin diseases and suspected of causing birth defects and cancer.
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