Homofermenters and Heterofermenters

Lactic acid bacteria can be broadly categorized into two groups based on how they ferment hexose (6-carbon) sugars like glucose and fructose. Homofermentative LAB convert each molecule of 6 carbon sugar into two 3 carbon molecules of lactic acid:
Glucose 2 Lactic acid + 2 H2O
Fructose 2 Lactic acid + 2 H2O
Heterofermentative LAB produce a mixture of end products from
6 carbon sugars:
Glucose 1 Lactic acid + 1 Ethanol + 1 CO2 + 1 H2O and
3 Fructose 1 Lactic acid + 1 Acetic acid +
2 Mannitol + 1 CO2 + 1 H2O
So, using a mixture of 3 glucose and 3 fructose, the end products of
the two types of LAB would be:
Homofermenters: 12 Lactic acid + 12 H2O
Heterofermenters: 4 Lactic acid + 1 Aectic acid + 3 Ethanol
+ 2 Mannitol + 4 CO2 + 4 H2O
The heterofermentative LAB produce significantly less acid (slower pH
drop) and also produce carbon dioxide (loss of dry matter and energy),
ethanol (depending on levels it can increase or decrease palatability)
and mannitol (decreases palatability).