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Aglycone production by Lactobacillus rhamnosus CRL981 during soymilk fermentation

Marazza, Jose A., Garro, Marisa S., Savoy de Giori, Graciela
Food microbiology 2009 v.26 no.3 pp. 333-339
soymilk, starter cultures, Lactobacillus rhamnosus, fermentation, lactic acid bacteria, beta-glucosidase, enzyme activity, pH, temperature, viability, glucosides, isoflavones, sugars, fermented foods, storage quality, thermal stability
Lactobacillus rhamnosus CRL981 showed the highest levels of β-glucosidase and was selected to characterize this enzyme system, among 63 strains of different Lactobacillus species. The maximum activity was obtained at pH 6.4 and 42 °C. The enzyme showed weak resistance to thermal inactivation maintaining only 20% of the initial activity when it was exposed at 50 °C for 5 min. It also, showed stability when stored at 4 °C for 60 days. Afterwards, L. rhamnosus was evaluated for hydrolysis of isoflavones to aglycones, cell population, residual sugars and organic acid produced during fermentation on soymilk (37 °C for 24 h). Higher viable counts were obtained after 12 h of fermentation (8.85 log CFU ml-1) followed by a drop of pH and an increase of acidity during fermentation due the production of organic acids. L. rhamnosus CRL981 was able to proliferate in soymilk and produce a high β-glucosidase activity achieving a complete hydrolysis of glucoside isoflavones after 12 h of fermentation. The present study indicates that L. rhamnosus CRL981 could be used in the development of different aglycone-rich functional soy beverages.