A good producer of citric acid is:
Saccharomyces
Aspergillus
Pseudomonas
Clostridium
A good producer of citric acid is Aspergillus niger (a fungus). Clostridium produces butyric acid, Saccharomyces cerevisiae is used for bread baking fermenting malted cereals and fruit juices to produce ethanol. Pseudomonas (a bacterium) is used in Vitamin -B-12 production.