Bacterial Fermentation

• ATP is produced only by substrate level phosphorylation

• Also ion gradient driven phosphorylation Proton or sodium ion and is generated by

• electron transport• Decarboxylation• Ion-coupled end product effux• substrate.-product antiport

Types of substrate used

• Sugars

• Polyols• Organic acids• Amino acids• Purines • Pyrimidines

ATP yield

• 0.3 – 4 mol ATP

Ethanol fermentation• Glucose 2CO2 + 2 ethanol

YEAST2 mol ATP per mol substrate

Zymomonas1 mol ATP per mol glucose

Lactic acid fermentation

Lactic acid bacteria

Homofermentative Heterofermentative

Glucose 2 lactate2 mol ATP per mol glucose

glucose CO2+lactate+ethanol1 mol per mol glucose

Propionate fermentation

3 lactate 2 propionate + acetate + CO2

• Acrylate pathway0.3 mol ATP per mol lactate

• Methylmalonyl-CoA pathway

Mixed acid and butanediol fermentation

• Mixed acid fermentation Ratio acid to neutral products 4:1Ratio H to CO2 1:1

• Butanediol fermentationRatio acid to neutral products 1:6Ratio H to CO2 1:5

Butyrate and acetone-butanol fermentation

• Butyrate fermentationGlucose butyrate + 2CO2 + 2H23mol ATP

• Butanol fermentation2 glucose butanol + acetone + 4H2 + 5CO22.5mol ATP

Homoacetate fermentation

• Moorella thermoacetica• Acetobacterium woodii

• Glucose 3 acetate

Distribution of fermentation among organism

• Eukaryotes

• Bacteria • Fungi• Worms (Ascaris lumbricoides)