Earlier, it was considered that PUFA are absent in bacteria due to
acyl functions of the complex lipids in their membranes.
However, recently, many marine bacterial species comprising high amount of EPA and DHA have been discovered.
Especially, species found in high pressure and low temperature deep sea environments are potent producers of PUFAs (Table 4).
It has been speculated that bacterial species in such extreme environment produce high amount of PUFA as an adaptation for the elevated hydrostatic pressure and to decreasemembrane fluidity in low temperature (Allen & Bartlett, 2000; Kawamoto et al., 2009).
However, high pressure and lowtemperature culture conditions are not considered as cost effective approaches in commercial productions.
Moreover, marine bacteria, particularly those found in the gut flora of fish in deep low temperature waters, produce high amount of PUFAs.
The plus point of these bacterial species is that those species can be grown in large-scale artificial fermenters to produce omega-3 fatty acids in sustainable manner.
Meanwhile, recent advanced technical developments have facilitated rapid screening and isolation of EPA producing marine bacteria from mixed cultures.
Further, various fungal and yeast species have also been identified as potential alternative sources for production of long chain PUFA.
Oleaginous soil fungal strains' Mortierella spp. were
found to be a promising source of C20 PUFAs production with Mortierella alpina's ability to produce high level of EPA when growth temperature is below 20 °C.
However, marine fungal and yeast strains have received less attention in regard to PUFA production. Khot et al. (2012) reported that many marine fungal species accumulate over 20% (w/w) of their dry cell mass as neutral lipids.