Transcript 發酵作用 - web

Fermentation
• Fermentation (發酵) is the term used by
microbiologists to describe any process for the
production of a product by means of the
mass (大量) culture (培養) of a
microorganism.
• The product can either be:
• 1. The cell itself: referred to as biomass (生物
質量) production.
• 2. A microorganisms own metabolite (代謝產
物) : referred to as a product from a natural
or genetically improved strain (品系).
• 3. A microorganisms foreign (外來) product:
referred to as a product from recombinant
(重組) DNA technology or genetically
engineered (基因工程) strain, i.e.
recombinant strain.
Products produced by microbial activity
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Amino acids (胺基酸)
Antibacterial agents (殺菌劑)
Antifungal agents (殺真菌劑)
Antiprotozoal agents (殺原蟲劑)
Carbohydrates
Dyes and cosmetics (顏料和化妝品)
Enzymes (酵素)
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Foods
Lipids (脂質)
Nucleotides (核甘酸) and precursors
Organic synthesis intermediates (中間物)
Pharmaceutical (藥物) significant compounds
Plant growth factors
Steroids (類固醇)
• Toxins (毒素)
• Vitamins and coenzymes (維生素和輔酶)
Products being addressed by
recombinant technology
• Human therapeutics (治療法)
• Enzymes
• Amino acids
Classification of microorganisms
• The kingdom Protista comprises unicellular
organisms capable of self duplication (複製品)
or of directing their own replication (複製).
Prokaryotes (原核生物) do not possess a true
nucleus (細胞核) or a nuclear membrane,
whereas eukaryotes (真核生物) have a nucleus
enclosed within a distinct nuclear membrane.
• The non-cellular protists (單細胞生物) do not
undergo self-replication, instead they direct
their reproduction within another cell termed
the host (寄主).
• Cyanobacteria (blue-green algae) have been
classified as a separate group of
microorganisms, although they are frequently
considered to be included with other bacteria.
• Fungi (真菌) may be subdivided into lower
fungi as well as slime moulds (黴菌) and
higher fungi which comprises (包含) yeast’s.
Yeast’s (酵母菌) are free-living, single cells,
unlike fungi, which they closely resemble.
• Protozoa are free-living, minute organisms,
which although not generally employed for
biotechnological processes have been included
for completeness.
• Myxomycota (變形體黏菌), commonly
known as slime moulds (or slime fungi) are
widely used as research organisms. Viruses
can be regarded as intracellular (細胞內)
parasites (寄生蟲).
Fermentation in food processing
• Natural fermentation precedes (早於) human
history. Since ancient times, however, humans
have been controlling the fermentation process.
The earliest evidence of an alcoholic beverage,
made from fruit, rice, and honey, dates from
7000–6600 BCE (Before the Common Era) , in
the Neolithic (新石器時代) Chinese village of
Jiahu, and winemaking dates from 6000 BCE,
in Georgia.
• Seven-thousand-year-old jars containing
the remains of wine, now on display at the
University of Pennsylvania, were
excavated (發掘) in the Zagros Mountains
in Iran. There is strong evidence that
people were fermenting beverages in
Babylon circa (大約於) 3000 BC, ancient
Egypt circa 3150 BC, pre-Hispanic Mexico
circa 2000 BC, and Sudan circa 1500 BC.
• French chemist Louis Pasteur (巴斯德) was
the first known zymologist (發酵學家), when
in 1856 he connected yeast to fermentation.
Pasteur originally defined fermentation as
"respiration without air". Pasteur performed
careful research and concluded:
• The primary benefit of fermentation is the
conversion of sugars and other carbohydrates
into preservative organic acids, e.g. converting
juice into wine, grains into beer, carbohydrates
into carbon dioxide to leaven (發鬆) bread,
and sugars in vegetables.
Food fermentation
• Enrichment of the diet through development of
a diversity of flavors (風味), aromas (氣味),
and textures (質地) in food substrates
• Preservation of substantial amounts of food
through lactic acid (乳酸), alcohol, acetic acid
(醋酸), and alkaline (鹼性) fermentations
• Biological enrichment of food substrates with
protein, essential (必要) amino acids, and
vitamins
• Elimination (排除) of antinutrients (抗養分)
• A decrease in cooking time and fuel
requirement
Fermented foods by type
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Bean-based (natto, soy sauce, stinky tofu)
Grain-based (beer, bread, sake , vodka)
Vegetable based (Kimchi, pickle,)
Fruit based (Wine, vinegar,)
Honey based (Mead, metheglin)
Dairy based (Cheese, yogurt)
Fish based (fish sauce, shrimp paste,)
• Meat based (Pepperoni)
• Tea based (Pu-erh tea, Kombucha)
Risks of consuming fermented foods
• Alaska has witnessed a steady increase of
cases of botulism since 1985. This is
caused by the traditional Eskimo practice
of allowing animal products to ferment for
an extended period of time before being
consumed.
• The risk is exacerbated when a plastic
container is used for this purpose instead of the
old-fashioned, traditional method, a grass-lined
hole, as the botulinum bacteria thrive in the
anaerobic conditions created by the air-tight
enclosure in plastic.
• The World Health Organization has classified
pickled (醃漬) foods as a possible carcinogen,
based on epidemiological (流行病學) studies.
Other research found that fermented food
contains a carcinogenic by-product (副產品),
ethyl carbamate (urethane,氨基甲酸酯).
• "A 2009 review of the existing studies
conducted across Asia concluded that regularly
eating pickled vegetables roughly doubles a
person's risk for esophageal squamous cell
carcinoma.“###