Polyunsaturated fatty acid production by marine bacteria

Abstract

Polyunsaturated fatty acids are important in maintaining human health. Limitations associated with current sources of ω-3 fatty acids and ω-6 fatty acids, from animal and plant sources, have led to increased interest in microbial production. Marine bacteria may provide a suitable alternative, although the isolation of production strains and the identification of operating conditions must be addressed before manufacturing processes become economically viable. Marine isolate 560 was identified as an eicosapentaenoic acid (EPA) producer via GC/MS. The isolate was initially identified as Vibrio cyclitrophicus by 16S rRNA sequencing. Statistically based experimental designs were applied to the optimisation of medium components and environmental factors for the production of EPA. A Plackett-Burman design was used to screen for the effect of temperature, pH, and media components. Subsequently, the concentrations of NaCl, yeast extract, and peptone, identified as significant factors, were optimised using a central composite design. The predicted optimal combination of media components for maximum EPA production (4.8 mg/g dry weight) was determined as 7.9 g/l peptone, 16.2 g/l NaCl, and 6.2 g/l yeast extract. On transfer of this process to bioreactor cultivation, where a range of pH and DO values were tested, the maximum amount of EPA produced increased to 7.5 mg/g dry weight and 10 % of the total fatty acid.

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“…However, we have been successful in isolating PUFA producers from the Arabian Sea along the Indian western coast; falling in the tropical belt generally having ambient temperatures around the year. This information goes contrary to the common notion that only psychrophilic and halotolerant microorganisms from the colder regions of the world are able to produce PUFA 2,5,19 .…”

“…Since then, it has been confirmed that PUFA production occurs in numerous bacterial species isolated from Antarctic regions as well as temperate marine environments. Attention of many researchers has thus been centered on cold seas and deep oceans 2,5,8,19 . However, we have been successful in isolating PUFA producers from the Arabian Sea along the Indian western coast; falling in the tropical belt generally having ambient temperatures around the year.…”

“…In the quest to identify newer and economical sources of the highly valuable polyunsaturated fatty acids (PUFA) many researchers have identified numerous psychrophilic taxa of microorganisms possessing this unusual ability 2 . Although fish oils and plants were primarily considered to be the main source of polyunsaturated fatty acids (PUFA) since the last two decades the production of PUFA by bacteria is being developed as an alternative technique 2,3,4,5 .…”

“…Due to the many shortcomings of fish-derived oil including undesirable taste and odour, diminishing supplies, reluctance to consumption by vegetarians, its non-ecofreindly chemical processing methods like bleaching and deodorizing, and the likely presence of contaminants such as mercury, dioxins and polychlorinated biphenyls, research has been diverted towards the exploitation of other marine species for the development of suitable alternatives. Numerous organisms including bacteria, yeast, filamentous fungi, and microalgae have been reported to produce different types of polyunsaturated fatty acids 1,2,5,7 .…”

“…Several strains belonging to the genus Shewanella isolated from cold water environments have been reported as being high-level PUFA-producing microorganisms. Besides these, strains belonging to the genera Colwellia, Photobacterium, Flexibacter, Vibrio and Moritella are also PUFA-producing microorganisms 2,4,5,10 .…”