Bacterial production of polyunsaturated fatty acids (PUFAs) is a potential biotechnological approach for production of valuable nutraceuticals. Reliable method for screening of number of strains within short period of time is great need. Here, we report a novel simplified method for screening and isolation of PUFA-producing bacteria by direct visualization using the H2O2-plate assay. The oxidative stability of PUFAs in growing bacteria towards added H2O2 is a distinguishing characteristic between the PUFAs producers (no zone of inhibition) and non-PUFAs producers (zone of inhibition) by direct visualization. The confirmation of assay results was performed by injecting fatty acid methyl esters (FAMEs) produced by selected marine bacteria to Gas Chromatography-Mass Spectrometry (GCMS). To date, this assay is the most effective, inexpensive, and specific method for bacteria producing PUFAs and shows drastically reduction in the number of samples thus saves the time, effort, and cost of screening and isolating strains of bacterial PUFAs producers. 1. Introduction Microbial lipids are a diverse group of compounds with a number of vital nutraceutical and pharmaceutical applications and utilized commercially since the 1980s. These microbial lipids or polyunsaturated fatty acids (PUFAs) are obtained from various sources. Now a day, microorganism-produced (algae/fungi/bacteria) PUFAs are commercially competitive with plant and fish oils. PUFAs are the fatty acids having more than one double bond. Eicosapentaenoic acid (EPA, 20？:？5, n-3) and docosahexaenoic acid (DHA, 22？:？6, n-3) are the important n-3 fatty acids, while arachidonic acid (AA, 20？:？4, n-6) is a vital n-6 fatty acid. EPA and DHA are important for prevention of arthrosclerosis, cancer, rheumatoid arthritis, psoriasis, and diseases of old age such as Alzheimer’s and age-related macular degeneration [1, 2]. AA and DHA are of special importance in the brain and blood vessels and are considered essential for pre- and postnatal brain and retinal development [3]. Eicosanoids such as prostaglandins, prostacyclins, and leukotrienes derived from n-3 PUFA are also important in new-born and infant development, modulatory vascular resistance, and wound healing [4–6]. PUFAs are either directly available as components of the diet or produced from precursors like linoleic acid (LA, C18？:？2 n-6) and a-linolenic acid (ALA, C18？:？3 n-3) [7]. Accordingly, PUFAs are highly important substances in the pharmaceutical, medical, and nutritional fields. Recent investigations have focused on microorganisms as alternative
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