1 / 17

Yoon-Hee Lee Dep. of Food Science & Technology

Y easts and M olds - Using selective media; examining fungi morphology. Yoon-Hee Lee Dep. of Food Science & Technology. FUNGI VS. BACTERIA. Fungi ۰ Larger ۰ Eukaryotic ۰ Aerobic ۰ Slow growth ۰ Grow in both acidic and basic condition ۰ Filamentous - Mycelia. Bacteria ۰ Smaller

marsha
Télécharger la présentation

Yoon-Hee Lee Dep. of Food Science & Technology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. YeastsandMolds - Using selective media; examining fungi morphology Yoon-Hee Lee Dep. of Food Science & Technology TheOhioStateUniversity

  2. FUNGI VS. BACTERIA Fungi ۰ Larger ۰ Eukaryotic ۰ Aerobic ۰ Slow growth ۰ Grow in both acidic and basic condition ۰ Filamentous - Mycelia Bacteria ۰ Smaller ۰ Prokaryotic ۰ Aerobic and Anaerobic ۰ Fast growth ۰ Prefer neutral media TheOhioStateUniversity

  3. CLASSIFICATION OF FUNGI ☞ Fungi kingdom (yeasts and molds) • Subkingdom: based on septation of mycelia • Phylum: based on ability to produce and type of sexual spores TheOhioStateUniversity

  4. UBIQUITOUS IN FOOD - Spoilage • Toxicity • Fermented foods • Food additives & processing aids TheOhioStateUniversity

  5. FUNGI OF INTEREST ☞ Yeasts: • Saccharomyces spp. • Zygosaccaromyces spp. • Candida spp. ☞ Molds: • Rhizopus spp. • Asperigillus spp. • Penicillum spp. TheOhioStateUniversity

  6. BUDDING YEAST (Saccharomyces spp.) - The Bakers’ and Brewer’s yeast • Most yeasts, including Saccharomyces reproduce by budding • does not ferment lactose • White or cream colonies • Typical yeasty odor TheOhioStateUniversity

  7. Rhizopus spp. - Nonseptate, root-like structure • Umbrella-shaped columellae • Large sporangiospore with striated wall • Dark sporangia containing dark to pale spore TheOhioStateUniversity

  8. Penicillium spp. - P. digitarum: yellow green conidia • P. italicum and P. expansum: blue-green conidia • P. camemberti: grey conidia TheOhioStateUniversity

  9. Aspergillus spp. - Black, brownish black, purple brown conidiophore • Yellow to green conidia • Dark sclerotia • A. niger: black rot on fruits and vegetables TheOhioStateUniversity

  10. OBJECTIVES ☞ Enumeration of yeasts and molds (difference between processed and fresh grapefruit juices) ☞ Importance of selective and differential media ☞ Compare and contrast fungi morphology macroscopically and microscopically TheOhioStateUniversity

  11. DEFINITION • ☞ Selective media • Allow microorganisms of interest to grow and have a selective advantage over otherwise competing organisms • Contain selective agents • ☞ Deferential media • Distinguish between two microorganisms based on a single or multiple biochemical properties • Contain differential agents TheOhioStateUniversity

  12. SELECTIVE MEDIA • ☞Acidified Potato Dextrose Agar (PDA) • Tartaric acid lowers pH to inhibit bacterial growth • Note: Some acid-tolerant bacteria can still grow leading to an over-estimate of fungi count ☞Antibiotic TSA (Not PCA) - Chloramphenicol and chlortetracycline inhibit bacteria TheOhioStateUniversity

  13. MEDIA CONT’D • ☞Petrifilms • Selective and differential for yeasts and molds • Contain chlortetracycline and chloramphenicol • Indicator: bromo-chloro-indolylphosphate gives yeast a blue-green color • Yeasts: small and defined • Molds: larger and diffuse TheOhioStateUniversity

  14. LAB PERIOD 1 ☞ Cut grapefruit in half and extract juice • Refrigerate (4 °C) it until used ☞ Reconstitute frozen concentrated grapefruit juice • Mix water (about three can) and one can of frozen concentrated grapefruit juice • - Refrigerate (4 °C) it until used. TheOhioStateUniversity

  15. LAB PERIOD 1 ☞ Prepare media: • Add tartaric acid to the PDA • Add antibiotic solution to the TSA • Allow plates to dry 24-48 hours TheOhioStateUniversity

  16. LAB PERIOD 2 ☞ Take 10 ml sample and Prepare 10-1 and 10-2 dilution of the sample using the 9 ml peptone blanks • ☞Spread plate dilutions in duplicate onto Acidified PDA (6) and antibiotic TSA (6) • ☞Transfer 1 ml of the dilutions 10-1 and 10-2 onto Petrifilms • Do not use undiluted sample because this produces artifacts • ☞Incubate at 25 °C for 5 days TheOhioStateUniversity

  17. LAB PERIOD 3 ☞ Enumerate plates • ☞Pick 3 yeast colonies and examine different colony morphologies (macroscopically) and microscopically • ☞Place a drop of lactophenol cotton blue dye on a slide and place tape with mold onto surface – examine micro/macroscopically • Lactic acid: preserve fungal structures • Phenol: killing agent • ☞View demo microscope slides • ☞ Draw and record morphologies TheOhioStateUniversity

More Related