Hydrocarbon Production - Hydrocarbons produced by some microorganisms may also serve as liquid or gaseous fuels.

For instance, microbial production of methane gas from polymers like carbohydrates, proteins, lipids, etc.

involves following three steps:

(i) breakdown of polymers into organic acids and alcohols by hydrolytic and fermentation bacteria;

(ii) conversion of acids and alcohols into acetates, H2 and CO2 by the hydrogen producing acetogenic bacteria and

(iii) conversion of acetate and H2 + CO2 to methane by methanogenic bacteria