BIOL 2P98 Lecture Notes - Leuconostoc, Lactose Intolerance, Soy Sauce
5 May 2018
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Chapter 3,14,15: Fermentation
• Lactobacilli: makers of cheese and sauerkraut
o Non-sporulating Gram positive bacteira
o Staphylococcus, streptococcus, lactobacillus, leuconostoc
• Saccharomyces: makers of ethanol
• Fermented Foods Overview
o Fermentation is the treatment with microbes, it is the reduction of pyruvate or a derivative of it
o The microbes digest food first
o Preserves food -> makes the food inedible for predatory microbes -> alcohol buildup
o Makes food digestible by breaking down indigestible fibres
o Adds nutrients -> microbially-produced vitamins
• First: Lactic acid as a fermentation production Acidic Dairy Fermentation
o Milk is coagulated by the bacteria which forms curds
▪ The lactose is digested and is fermented to lactic acid
• Cheese/yogurt is safe for lactose intolerant people
o Proteases (rennet) cuts up milk protein -> coagulates the curd to make harder cheese
o Further fermentation occurs
o Propionibacterium prodcues CO2 gas-swiss cheese?
o Fermentation by Penicillium mold- blue cheese?
• Other Acidic Animal Product Fermentations
o Lactobacillus -> yogurt, kefir, sausage
o Lactococcus -> buttermilk, sour cream
o Streptococcus -> yogurt, kefir
o Others -> fish, many types of sausage
• Acidic Vegetable Fermentations
o Soybeans
▪ The microbes remove harmful elements
• Mold: Phizopus -> Tempeh
• Mold: Aspergillus: Miso, Soy sauce
o Cabbage, cucumbers, olives
▪ Leuconostoc: sauerkraut, pickles, olivers, kimchi
• Lactobacillus
o Most species of this non-spore-forming bacterium ferment glucose or lactose into lactic acid
o Aerotolerant anaerobes
o The most common application of Lactobacillus is industrial-> dairy production
o This genus also contains several bacteria that make up par of the natural flora in the human vagina
▪ Because of their ability to derive lactic aicd from glucose, these bacteira create an acidic environment
which inhibits growth of many bacterial seocies that lead to urogenital infections
▪ Lactobacillus is generally harmless to humans, rarely inciting harmful infections or diseases
• Inoculation and Milk Ripening
o Cheesemaking relies on the fermentation of lactose by lactic acid bacteria (LAB)
o LAB produce lactic acid which lowers the pH which assists in coagulation, helps prevent spoilage and
pathogenic bacteria from growing, contributes to cheese texture/flavour/quality
o LAB also produce growth factors which encourages the growth of non-started organisms and provides lipases
and proteases necessary for flavour development during curing
• Streptococcus for Buttermilk
o Aroma production (biacetyl & volatile acids) from Leuconostoc
o Tangy flavour in sausages due to LAB
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Document Summary
Lactobacillus is generally harmless to humans, rarely inciting harmful infections or diseases. In the past there were two types of beer yeast -> ale yeast (top fermenting type, saccharomyces cerevisiae) and the lager yeast (bottom-fermenting type, saccharomyces uvarum formerly known as s. carlsbergensis: fermentation. I(cid:374) fer(cid:373)e(cid:374)tatio(cid:374), atp sy(cid:374)thesis o(cid:272)(cid:272)urs due to lp, a(cid:374) i(cid:374)ter(cid:373)ediate su(cid:271)strate (cid:271)e(cid:272)o(cid:373)es (cid:862)high e(cid:374)ergy(cid:863) a(cid:374)d eventually trasfter phosphate from adp to atp. In respiration, the cytoplasmic membrane is energized by pmf resuling in atp formation. Pmf is coupled to atp formation & energy transferred by membrane bound atp synthase: 5) energy yields are low, slp is an inefficient process & much of the energy of the electrons is lost. Infection occurs when normal balance in vagina changes and yeast cells overgrow: overgrowth has several possible causes, one cause may be a change in hormone levels, a second could be antibiotics.
