Methods for identifying lipoxygenase producing microorganisms on agar plates

Lipoxygenases (EC 1.13.11.12, EC 1.13.11.34 and EC 1.13.11.33) are non-heme, iron or manganese containing enzymes which catalyze the oxidation of unsaturated fatty acids containing a 1-cis,4-cis-pentadiene structure to fatty acid hydroperoxides. Linoleic acid, linolenic acid and arachidonic acid are the natural substrates of lipoxygenases (Su and Oliw 1998; Goldsmith et al. 2002).Lipoxygenase catalyzed oxidative coupling reactions are utilized extensively in bread making. The addition of lipoxygenase-rich soybean flour results in the production of fatty acid hydroperoxides, which bleach the pigments of wheat flours. Lipoxygenase action also improves the mixing tolerance and rheological properties of the dough. (Frazier et al. 1973; Faubion and Hoseney 1981; Boussard et al. 2012. Furthermore, lipoxygenases have been used for bleaching dairy products such as cheese, milk, butter oil, cream, and whey (de Roos et al., 2006). Alcohols and aldehydes have been produced industrially from the fatty acid hydroperoxides that are formed in the lipoxygenase-catalyzed reactions. These compounds are used for flavouring foods (Whitehead et al. 1995).Lipoxygenases have been detected in plants Feussner and Wasternack (2002); Baysal and Demird？ven 2007), mammals (Hammarberg et al. 1993), and in eukaryotic (Su and Oliw 1998) and prokaryotic microorganisms (Koeduka et al. 2007; Vance et al. 2004). However, the recombinant production of secreted, stable lipoxygenases at high levels has only been achieved by the expression of the lipoxygenase gene of the fungus Gaeumannomyces graminis in Pichia pastoris (Cristea et al. 2005).Many different assays for lipoxygenases have been developed (Axelrod et al. 1981; Williams et al. 1986; Suda et al. 1995; Villafuerte Romero and Barrett 1997; Anthon and Barrett 2001). The majority of these assays are based on detecting the fatty acid hydroperoxides formed, either indirectly by colorimetry or directly by UV-spectroscopy. However, for screening micoorg