1. THREE TYPES OF FOOD FERMENTATION
Alcohol
Acetic Acid
Lactic Acid - Largest of all
Homofermentative
Heterofermentative

2. Bacteria lactic acid bacteria acetic acid bacteria food bioprocessing food biopreservation Probiotic

3. FOOD FERMENTATIONS Lactic Acid Bacteria SWEET PICKLES
Vegetables and Fruits
SWEET
PICKLES

4. Lactobacillus helveticus
Lactobacillus delbrueckii sub. bulgaricus
Lactobacillus lactis

5. Fermented Milks
majority of fermented milk products rely on lactic acid bacteria belonging to the genera Lactobacillus, Lactococcus, Leuconostoc, and Streptococcus
gram-positives that tolerate acidic conditions, are non-spore forming, and are aerotolerant with a strictly fermentative metabolism

6. Fermented Milks… mesophilic thermophilic probiotics
Lactobacillus and Lactococcus
buttermilk and sour cream
thermophilic
Lactobacillus and Streptococcus
yogurt
probiotics
Lactobacillus and Bifidobacterium
addition of microbes to the diet to improve health beyond basic nutritive value

8. FOOD FERMENTATIONS
Lactic Acid Bacteria
Meats

9. FOOD FERMENTATIONS
Lactic Acid Bacteria
Dairy Products

10. FOOD FERMENTATIONS Lactic acid with other microbes Dairy Products
With other bacteria
With yeasts
With molds
Vegetable Products

11. Lactic acid bacteria (LAB)
G+, non-spore forming cocci or rods
Microaerophilic or anaerobic
Metabolize carbohydrates through fermentative pathways
Acid production as the major end-product
Common genera
Lactococcus, Lactobacillus, Leuconostoc, Pediococcus, Streptococcus, Oenococcus

12. Lactic Acid Bacteria
Gram (+) rods (Lactobacillus) and cocci (Streptococcus, Lactococcus, Leuconostoc)
Produce large amount of lactic acid
Aerotolerant anaerobes: grow fermentatively
Require many growth factors (vitamins and amino acids)
Found in nutrient-rich environments (decomposition)

13. Lactic Acid Bacteria Used to ferment or culture foods for 4000 years
Used in fermenting yogurt, cheese, butter, kefir and in pickling vegetables
Lactose (milk sugar) converted to lactic acid; low pH precipitates protein, causing curdling
Low pH also inhibits growth of other bacteria
Give tart taste to fermented milks
Growth is self-limiting (build up of waste products)
Used in probiotics (presence in livestock feed inhibits E. coli)
Also produce bacteriocins (antimicrobial agents)

14. Lactic Acid Bacteria Produce large amount of lactic acid, lowering pH
Can grow at < pH 5
Predominate in acidic environment if it:
Is anaerobic
Is rich in nutrients
Contains a fermentable carbohydrate

15. Lactic Acid Bacteria: Divisions
Group I: Strict homofermenters
Group II: Facultative heterofermenters
Group III: Strict heterofermenters

16. Homofermentative Metabolism
85% of Glucose Lactic acid
Glucose Pyruvate via glycolytic pathway
HO-C-C-CH Pyruvate
HO-C-CH-CH Lactate
O O
NADH2
NAD+
O OH

17. Heterofermentative Metabolism
Organisms metabolize glucose via the pentose phosphate pathway.
End products can vary depending upon level of aeration and presence of other proton and electron acceptors. Acetyl-phosphate can be converted to acetate and ATP or reduced to ethanol without ATP production.

18. Pentose Phosphate Pathway
Lactic Acid Bacteria can also metabolize pentoses such as ribose, arabinose and xylose, via the pentose phosphate pathway.
Acetyl-phosphate leads to the generation of acetate and ATP exclusively in pentose metabolism.

19. Pentose Phosphate Pathway
Glucose
Phospho-6-gluconate
ATP ADP
NADP+
NADPH
CO2
Ribulose 5-phosphate
NADP+
NADPH
Xylulose 5-phosphate
Acetyl-phosphate
Glyceraldehyde 3- phosphate
NADH
NAD+
ADP
ATP
ADP
ATP
(glycolysis)
Acetate
Acetaldehyde
Pyruate
NADH
NAD+
Ethanol
Lactate

20. Lactic Acid Bacteria: Genera
Oenococcus
Pediococcus
Lactobacillus
Leuconostoc

21. Lactobacillus L. bavaricus L. casei L. homohoichii L. curvatus L. saki
Homolactic on hexoses
L. bavaricus
L. casei
L. homohoichii
L. curvatus
L. saki
L. plantarum
Heterolactic on hexoses
L. fermentum
L. brevis
L. buchneri
L. fructovorans
L. hilgardii

22. Bacteriocins
Antimicrobial peptides produced by some bacteria that inhibit closely related species
Membrane-active agents that form pores in cytoplasmic membrane and dissipate proton-motive force
Significant in food safety to control pathogens
Lactococcus lactis subsp. lactis and NISIN

23. Nisin Class I bacteriocin: lantibiotic, <5 KDa
Producer: Lactococcus lactis subsp. lactis
Active against G+ bacteria (Clostridium botulinum, Listeria monocytogenes, LAB)
Commercially available
Cheese and dairy products, canned foods, mayonnaise
Only bacteriocin approved for use in U.S.