Microbes in Biology

5–10 µm

20 – 30°C

Forming spores

Facultative anaerobic

Fungal spores

Bacteria

Food Microbiology

Microalgae

Fungi

Humidity

Staining with crystal violet-iodine complex

10nm for viruses, 1µm for bacteria

By inserting genetic materials into host cells

Chlorella zofingiensis

Single-celled, eukaryotic organisms

Archaebacteria

Cell shape, size, and structure arrangement

Protista

All of the above

Based on specific characteristics such as cell shape, size, and structure arrangement

Archaebacteria

Cholera, avian influenza, and ciguatera food poisoning

Based on their cell shape, size, and structure arrangement

Both single-celled (yeasts) and multi-celled (molds) organisms

By serving as a source of drugs

The six kingdoms into which microorganisms are classified include Protista, Fungi, Archaebacteria, Eubacteria, Plantae, and Animalia.

Microorganisms are classified based on characteristics such as cell shape, size, and structure arrangement.

Microorganisms can be detected in food using specific methods.

Examples of foodborne diseases caused by microorganisms include cholera, avian influenza, and ciguatera food poisoning.

Protista can exhibit different modes of growth like photoautotrophic, heterotrophic, and mixotrophic.

The classification of microorganisms mentioned in the text includes prokaryotic microorganisms (e.g. bacteria), eukaryotic microorganisms (e.g. fungi, microalgae, protozoa), and viruses.

The factors affecting microbial growth mentioned in the text are nutrition, temperature, pH, light requirement, and the growth curve.

Beneficial applications of microorganisms in daily life mentioned in the text include the production of foods such as beer, cheese, and soy sauce, as well as the production of nutritional foods like Spirulina cereal and Fat Choi.

The nutritional supplements and antioxidants mentioned to be produced by microorganisms include phycocyanin produced by Spirulina, omega-6 & omega-3 polyunsaturated fatty acids (PUFAs) such as Arachidonic acid (AA) produced by fungi, and Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) produced by diatoms and dinoflagellates.

The text mentions the production of fermented foods by microorganisms, giving examples such as the production of foods through fermentation.

Molds contain thread-like filaments called hyphae, and when hyphae extend and form a large mass, it is called a mycelium. They reproduce by forming spores, which disperse from the parent and germinate under favorable conditions.

Yeasts are single-celled, eukaryotic organisms that grow best at pH 4.5 – 5 and at a temperature of 20 – 30°C. They can grow in the presence and absence of oxygen (facultative anaerobic). Yeasts are important in the food industry as starters for producing fermented foods.

Microbes that require oxygen for growth are classified as aerobic, while those inhibited by oxygen are classified as anaerobic. Facultative anaerobic microbes can grow in both aerobic and anaerobic environments. For example, Saccharomyces cerevisiae can grow aerobically in the presence of oxygen and change to anaerobic growth when oxygen is deficient.

Agar plates/broth provide nutrients for bacterial growth, making them useful for maintaining and studying microbial cultures.

Yeasts, such as Saccharomyces cerevisiae, are crucial in the food industry as starters for producing fermented foods. This includes the production of bread, beer, and wine.

Bacteria gram staining involves fixed cells on a slide and staining with crystal violet-iodine complex.

Viruses have a size of 10nm, whereas bacteria cells have a size of 1µm.

Green microalgae like Chlamydomonas and Chlorella can reproduce asexually or sexually.

Chlorella zofingiensis is known for producing Astaxanthin, a red carotenoid, while Chlorella protothecoides produces Lutein, a yellow carotenoid.

Ciguatera, caused by Gambierdiscus toxicus, is an example of food poisoning caused by Protozoa.

Viruses are generally much smaller than bacteria and can only replicate inside the living cells of organisms.

Humans usually get infected with viruses via ingestion, shedding in feces, contaminated water sources, and food contamination caused by food handlers or carriers.

Primary contamination occurs when food is naturally contaminated during primary production. An example is filter-feeding shellfish being contaminated at the water source.

Secondary contamination is caused by food handlers, carriers, or the contaminated food preparation area.

Three common viruses causing foodborne illness are Norovirus, Rotavirus, and Hepatitis A virus.

The TDT curve shows the relationship between temperature and time needed to kill microorganisms.

The D-value is the time required to kill 90% of microbial population and varies with temperature.

Refrigeration (2-8˚C) slows microbial growth.

MAP alters the gaseous environment to preserve food freshness.

Dehydration inhibits microbial growth by reducing water activity.

Aims of food preservation include preventing spoilage, extending shelf life, minimizing spoilage microorganisms, and ensuring food safety. Principles of food preservation include the elimination or inactivation of microorganisms, stopping enzyme action, and preventing oxidation through physical, chemical, and biological methods of food preservation.

Norovirus symptoms include vomiting, diarrhea, fever, and nausea. It is mainly transmitted through hand-to-mouth contact, direct contact, and consumption of contaminated shellfish and salad.

Rotavirus causes vomiting, diarrhea, nausea, fever, and potentially death in severe cases. It is transmitted through fecal-oral and person-to-person transmission, food and waterborne.

Hepatitis A virus infection has an onset time of 12-50 days and symptoms including fatigue, diarrhea, liver damage, and extensive liver damage.

Molds primarily produce mycotoxins, causing foodborne illnesses like ergot poisoning from Claviceps purpurea, affecting neurons and leading to symptoms such as vision problems, confusion, unconsciousness, and gangrene in toes and fingers. Aflatoxin poisoning, caused by Aspergillus species, occurs in grains and nuts under damp and warm conditions, and its symptoms include liver degeneration, tumor, and stunted growth in children.

Pasteurization is a thermal process used to inactivate enzymes and eliminate viable pathogenic microorganisms from heat-sensitive foods such as milk, fruit juice, wine, and egg. It involves heating the food to below 100˚C for a specific duration and then rapidly cooling it to slow down microbial growth, requiring refrigeration storage and providing a shelf life of 2-3 weeks.

The two main methods of pasteurization are low-temperature pasteurization at 63˚C for 30 minutes and high-temperature short time (HTST) pasteurization at 72˚C for 15 seconds.

Ultra-high temperature (UHT) pasteurization of raw milk involves heating the milk to around 138 °C for 2-3 seconds, then rapidly cooling and packaging it in sterile, hermetically-sealed containers, providing a shelf-stable product for 6 months without requiring refrigeration until opened.

Sterilization is a process that completely kills or removes all life forms, including bacteria and other organisms, and is commonly achieved through heating methods such as wet heating at 121°C for 15-20 minutes.

D value represents the time needed to reduce the number of a given microorganism by 90% at a specific temperature, and it decreases as the temperature increases, differing for different microbial species.