Article

The importance of lactic acid bacteria for phytate degradation during cereal dough fermentation

Distaam, Università degli Studi del Molise, Via De Sanctis, 86100 Campobasso, Italy.
Journal of Agricultural and Food Chemistry (Impact Factor: 3.11). 05/2007; 55(8):2993-7. DOI: 10.1021/jf063507n
Source: PubMed

ABSTRACT Lactic acid fermentation of cereal flours resulted in a 100 (rye), 95-100 (wheat), and 39-47% (oat) reduction in phytate content within 24 h. The extent of phytate degradation was shown to be independent from the lactic acid bacteria strain used for fermentation. However, phytate degradation during cereal dough fermentation was positively correlated with endogenous plant phytase activity (rye, 6750 mU g(-1); wheat, 2930 mU g(-1); and oat, 23 mU g(-1)), and heat inactivation of the endogenous cereal phytases prior to lactic acid fermentation resulted in a complete loss of phytate degradation. Phytate degradation was restored after addition of a purified phytase to the liquid dough. Incubation of the cereal flours in buffered solutions resulted in a pH-dependent phytate degradation. The optimum of phytate degradation was shown to be around pH 5.5. Studies on phytase production of 50 lactic acid bacteria strains, previously isolated from sourdoughs, did not result in a significant production of intra- as well as extracellular phytase activity. Therefore, lactic acid bacteria do not participate directly in phytate degradation but provide favorable conditions for the endogenous cereal phytase activity by lowering the pH value.

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    • "Phytate degradations during fermentation range between 0 and 90% (Kruger, Taylor, & Oelofse, 2012; Reale et al., 2007; Reddy & Pierson, 1994; Towo, Matuschek, & Svanberg, 2006). This seems to be mainly related to the endogenous phytase activity of the plant matrix (Reale et al., 2007), since this correlation is not valid when grains or legumes are first heated before fermentation . It is known that the endogenous phytases are not stable at temperatures of 55 C or higher (Wodzinski & Ullah, 1996) and thus are deactivated during heating, resulting in a limited phytate degradation. "
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    • "Many factors are known to play a role in the rate and the extent to which IP6 is degraded, among which the endogenous phytase activities of the raw materials and the processing conditions like pH, which is known to modulate the activities of both plant and microbial phytases (Greiner & Konietzny, 2006). The higher endogenous phytase activity of flour blends containing barley and wheat is consistent with the results of previous studies showing higher activities for these cereals (Egli, Davidsson, Juillerat , Barclay, & Hurrell, 2002; Reale et al., 2007) and IP6 degradation under the range of optimal pH values observed for barley and wheat phytases (Greiner & Konietzny, 2006). Moreover, the addition of malt in BW-and WrS-injeras possibly helps create a favourable environment for yeasts with phytase activities, indeed some strains of yeast species like Saccharomyces cerevisiae are known to display phytase activity (Vats & Banerjee, 2004). "
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    • "Similar relationships between ash digestibility and lactose inclusion have been reported by O'Doherty et al. (2005). Research by Pierce et al. (2006) showed that high concentrations of lactose increased the concentration of lactic acid in the large intestine, which would provide favourable conditions for endogenous cereal phytase activity by lowering the pH of the hindgut (Reale et al., 2007). Increased phytase activity would enhance the phosphorus and mineral uptake in monogastric animals (Lassen et al., 2001). "
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