Osmophile

Osmophilic organisms are microorganisms adapted to environments with high osmotic pressures, such as high sugar concentrations. Osmophiles are similar to halophilic (salt-loving) organisms because a critical aspect of both types of environment is their low water activity, a_W. High sugar concentrations represent a growth-limiting factor for many microorganisms, yet osmophiles protect themselves against this high osmotic pressure by the synthesis of osmoprotectants such as alcohols and amino acids. Many osmophilic microorganisms are from the yeast lineage of fungi, however a variety of bacteria are also osmophilic.

Osmophile yeasts are important because they cause spoilage in the sugar and sweet goods industry, with products such as fruit juices, fruit juice concentrates, liquid sugars (such as golden syrup), honey and in some cases marzipan. Among the most osmophillic are:

Organism	Minimum aW
Saccharomyces rouxii	0.62
Saccharomyces bailii	0.80
Debaryomyces	0.83
Wallemia sebi	0.87		Saccharomyces cerevisiae	0.90

Pathogenicity

Osmophiles with possible pathogenesis are Aspergillus, Saccharomyces, Enterobacter aerogenes and Micrococcus. However, none of them are highly pathogenic, and only cause opportunistic infections, i.e. infections in people with weakened immune system. They are rather a cause of general food spoiling than causing any food poisoning in humans.