صفحه 1:
Lactic Acid Bacteria
Taxonomy and energy
metabolism
صفحه 2:
LAB
Lactic acid bacteria (LAB) - “milk-souring organisms.”
Gram positive
Nonsporulating
Catalase negative
Anaerobic but aerotolerant (facultative anaerobes)
Fastidious
Low mol% G+C
= Acid tolerant
= Strictly fermentative with lactic acid as the major end
product during sugar fermentation
= Some other G+ also produce lactic acid (Bacillus, Listeria,
Bifidobacterium)
صفحه 3:
Functions in the food
chain
= Dairy starter culture
=" Vegetable fermentation
= Alcoholic beverage fermentation
(3/4)
=" Meat fermentation
= Cereal fermentation
= Probiotics
صفحه 4:
LAB Classification and
Identification
= Phenotypic/biochemical characters
= Morphology
= Mode of glucose fermentation
= Growth at different temperatures
= Configuration of the LA produced
= Ability to grow at high salt concentrations
= Acid or alkaline tolerance
صفحه 5:
Lactic Acid Bacteria:
Classification
= Chemotaxonomic markers
= Fatty acid composition, constituents of the cell wall etc.
= Phylogenetic clusters do not correlate with
classification based on phenotypic characters
= New tools for classification and identification of
LAB
ا 0
= Partial rRNA-gene sequencing using PCR (16S, 23S rRNA
ene
0
صفحه 6:
Lactic Acid Bacteria:
Classification
BoE MSS o SUNT We festa tes Cre
12 genera (Fig. 2-2)
= Streptococcus-Lactococcus branch
Dip ara eos ETO
اعصفطط عبد مءمتل ع2 عبلللء قطم1 12«
« 0هرجم جاعصفعط ولاعوز ]ماده تمه نامسا- كبام
= Carnobacterium-Aerococcus-Enterocccus-Tetragenococcus-Vagococcus
ی Messe By
1 ECE MIU TC BHCC Meme Va
عمتامادهصه؟
Pee sits R UNA pe rettocec mon Co tee
صفحه 7:
Lactic Acid Bacteria:
Classification
= Aerococcus, Carnobacterium,
Vagococcus, Enterococcus,
Tetragenococcus, Leuconostoc,
Oenococcus, Weissella,
Lactobacillus, Lactococcus,
Pediococcus, Streptococcus (Table
2-2)
صفحه 8:
Figure 1. Schematic, unrooted phylogenetic tee of the lctic acid bacteria. Note: evolu
onary distances are approximate. Compiled from data by M. D. Collins and co-worker
(Collins ot al, 1989, 1990, 1991; Martines- Murcia and Collins, 1990; Walloank et al,
1900; Willa et al, 1991). A, Aerococeur, C, Carmobacterium; Ey Enterococcus; T.
صفحه 9:
LOW G+¢ SUBDIVISION
gure 2 Schematic representation of the phylogenetic position of lactic acid bacteria in
صفحه 10:
Energy Metabolism
= Glucose fermentation
= Glycolysis (Embden—Meyerhof pathway)
= Pentose phosphate pathway
= Four modes with various products (but all contain 5-C end
product or intermediate)
= TCA cycle
= Oxidative phosphorylation, electron-
transport chain
= Regenerate NAD*+
9 ات
صفحه 11:
صفحه 12:
صفحه 13:
‘THE COMPLETE OXIDATION OF GLUCOSE YIELDS
FROM 2670 30 Arr
‘cnt cle ai ia muy ATD are formed لق معدا
pletely ositized (Lite Viol tr he ghvcerol pesphate sve is
fhe overall تمده
Clucee 4.86 ADP4 اوه ام GO.
5 because 3h ATP ave formed ane! 2 tom 0 ااه
۱ bent
gcse nto pyr inte eo مارا
صفحه 14:
Common Energy Metabolism
in LAB
= Glycolysis (Embden—Meyerhof pathway)
--homolactic fermentation
= The 6-phosphogluconate/phosphoketolase
pathway--heterolactic fermentation
= Significance: fermentation end products relevant
to industrial applications
صفحه 15:
صفحه 16:
یت وعم + \— aa
مسر ۳
صفحه 17:
Lactococcus
= Consists of five phylogenetically-distinct
species: L. /actis, L. garviae, L. piscium, L.
plantuarum, L. raffinolactis
= Non-motile, obligate homofermentative,
facultative, facultative anaerobes, optimal
growth 30°C (mesophilic)
= Cocci, in pairs or short chains
صفحه 18:
Distinguishing characterisics of dairy
Lactococcus
Property Lactococcus lactis subsp. lactis L. lactis subsp. cremoris
Growth at 40C cP =
Growth in 4.0% NaCl if 2
Growth at pH 9.2 + -
Growth in 0.1% metgylene blue + -
Arginine hydrolysis + 3
Acid from maltose o =
Acid from ribose SP =
صفحه 19:
Streptococcus
= Non-motile, facultative anaerobes,
obligate homofermentative
= Used to contain four main groups
= Pyogenic,enterococcus, viridans, lactic
= Enterococcus and Lactococcus
removed from the genus
= S. thermophilus is the only member in
the genus used in food fermentation
صفحه 20:
S. thermophilus
Homolactic
Higher optimal growth temp (40-42C) than
L. latcis
Higher maximum growth temp (52C)
= Higher thermal tolerance (above 60C)
Weakly proteolytic, needs pre-formed
amino acids
Salt tolerance, bile sensitive, limited
metabolic diversity
صفحه 21:
Pediococccus spp.
Tetrads via cell division in two perpendicular
directions in a single plane
Acid tolerant, cannot synthesize porphyrins,
lactic acid as major metabolic end product
Strictly fermentative (homo) facultative anaerobic
Need rich media (N, aa, nicotinic acid,
pantothenic acid, biotin, some require other Vit)
Catalase- (some Pseudo+)
G+C 34-44%
Surface of plants and fruits
Become predominant microflora in fermenting
plant materials (silage, sauerkraut, olives, etc.)
Diversified, some grow in beer (spoilage) 91
Also found in cured meat, raw sausages, and ۲
marinated fish, and used in biotechnological 9»
processing and preservation of foods مب
bien
1
دیا
۱
صفحه 22:
Leuconostoc
G+, non-motile, mesophilic, opmimum growth temp 18-25C
۱ tm Me cota Meter stoty
Complex nutrient requirement
Obligately heterofermentative
5 ل ToC NTC =f ots
00 sie SAO net R csi Laat
1
19 Cee ore TetR TANT
بدمتغمتسعصحءة علءاعزم للثة قصه (ءودططدء لفكاعتم) غتتهعلدعتدد
0 ا tocaner loca ttettepi
۱ ا ا
19 ا mett nest tees
عمط هصق علهن 206ظ62و
ااه
صفحه 23:
Lactobacillus spp.
G+
Non-spore forming
Rods or coccobacilli
G+C usually below 50%
Strictly fermentative, aero-tolerant or anaerobic
Aciduric or acidophilic
Complex nutritional requirements (carb, aa,
peptides, FA, salts, nucleic acid derivatives, vit)
Homo or heterofermentative
صفحه 24:
Lactocobacillus
= Group |: obligate homofermenting
species
= Group II: facultative
heterofermenting species
= Group Ill: obligate heterofermenting
species (Table 2-5)
صفحه 25:
Lactobacillus
" Dairy starters: Lb. helveticus, Lb.
delbrueckii subsp. bulgaricus
= Lb. casei, Lb. acidophilus (probiotics)
= Sausage starter: Lb. plantarum, Lb.
sakei subsp. sakes
= Sourdough starter: Lb.
sanfranciscensis, Lb. brevis, etc.