Lab (Post-Midterm) Flashcards
what does SCOBY stand for?
symbiotic culture of bacteria and yeast
what agars were used with kombucha?
SD and nutrient agar
what does SD agar test for?
is it acidic or basic?
yeast
acidic medium
what does nutrient agar test for?
is it acidic or basic?
bacteria
basic medium
what are main LAB in kefir?
what are other MOs?
lactobacilli and lactococci
AAB and yeast
what media are used in kefir lab?
what does each one test for?
HHD: homo or heterofermentative LAB
MRS: presence of LAB
OGYE: yeast
in OGYE, what is the selective agent
oxytetracycline
what is the predominant organism of yogurt starter cultures?
LAB
what biochemical rxns occur in yogurt fermentation?
CHO –> lactic acid
caseins –> to peptides –> free AA
milk fat –> free FA
what agar is used in yogurt lab?
HHD
in HHD agar medium, what is the fermentable CHO?
what is the pH indicator?
fructose
bromo cresol green
in HHD again, what does heterofermentative LAB producce? what does homo LAB produce?
hetero: Co2, lactic acid, acetic aid, ethanol, mannitol
homo: produces only lactic
in yogurt, what color does homofermentative LAB produce?
yellow
due to producing lactic acid from fructose
in yogurt, what color does heterofermentative LAB produce?
varies in color depending on medium used
on HHD agar, what color does homofermentative LAB produce?
bluish-green colonies
on HHD agar, what color does heterofermentative LAB produce?
no color
what media were used in maple syrup lab?
nutrient agar
Sabouraud dextrose
what does SD agar test for in maple syrup lab?
fungi
what kind of maple syrup is more susceptible to fungi growth?
packaged maple syrup not sufficiently heated before sealing
or maple syrup stored for a long time after opening
describe the kerby-bauer method in the antibiotics lab
- diskcs with antimicrobial agents are placed on bacterial cultures on Mueller Hinton agar plates
- after incubation, zones of bacterial growth inhibition around the disk are measured and compared with standard zone size
what are the two media used in the antibiotics lab
muller hinton
TSA = tryptic soy agar
describe the muller hinton agar
- non-selective and non-differential
- many MOs will grow on it
- contains starch (absorbs toxins released from bacteria so they dont interfere with the antibiotics)
- “loose” agar: allows for diffusion of antibiotics through the media to give easier zone inhibition measurements
describe TSA
tryptic soy agar
- not selective or differential
- composed of digests of soybean meal and casein
- soy and casein peptones supply N, which makes it highly nutritious
- contains NaCl to maintain osmotic equilibrium
in spoilage due to underprocessing of canned food, what MOs will be present?
heat tolerant MOs
in spoilage due to can leakage of canned food, what MOs will be present?
hetergeneous
low heat resistance
what agars are used in the spoilage food lab?
what does each test for?
tomato serum media: lactobacillus species
nutrient agar: general MOs
plate count agar: bacterial growth
what broths are used in the spoilage food lab?
dextrose tryptone broth: MOs which produce acid from dextrose are detected by color change (purple to yellow)
liver broth: to examine saccharolytic or putrefactice mesophilic and thermophilic anaerobes. Bacterial growth produces increase in turbidity and/or gas
