According to me,its yeast culture used in submerged media and surface fermentation.

Surface fermentation refers to those fermentations in which the microorganisms utilised grows on the surface of the fermentation media.Examples being citric acid surface fermentation process wherein the microorganism aspergillus niger grows as a thick floating mycelial mat over the surface of the media used.

Submerged fermentation refers to those fermentations wherein microorganisms employed grows in submerged state within the fermentation media.many fermentations fall in this category like penicillin submerged fermentation technique

Submerged culture fermentation has been widely used for production of enzyme because in submerged fermentation unwanted metabolites are not produced and purification of enzymes takes place in easy way

almost submerged

submerged plants is plant which completely submerged in the water with their roots in the bottom mud.