ESTEROLYTIC ACTIVITIES OF INDIGENOUS LACTIC ACID BACTERIA ISOLATED FROM GOAT DAIRY PRODUCTS

NATALIA TABOADA; MARÍA C. ABEIJÓN MUKDSI ; SOLEDAD LOPEZ ALZOGARAY ; ROXANA B. MEDINA

San Miguel de Tucuman

Congreso; Congreso Argentino de Microbiologia General. SAMIGE BICENTENARIO; 2011

Sociedad Argentina de Microbiologia General

ESTEROLYTIC ACTIVITIES OF INDIGENOUS LACTIC ACID BACTERIA ISOLATED FROM GOAT DAIRY PRODUCTS Natalia Taboada 1, María C. Abeijón Mukdsi 2, Soledad López Alzogaray 1, Roxana B. Medina 2 1 -Facultad de Agronomía y Agroindustrias, UNSE, Santiago del Estero, Argentina 2- Centro de Referencia para Lactobacilos (CERELA-CONICET), Tucumán, Argentina. During cheese ripening, several flavor compounds arise from carbohydrate, citrate, protein and lipid metabolism. Lactic acid bacteria (LAB), the predominant microflora of many cheeses, have enzymatic systems (esterases and lipases) capable of hydrolyzing lipids. Esterases hydrolyze carboxyl ester linkages of water-soluble substrates, such as short-chain fatty acid (SCFA) esters and triglycerides composed of SCFAs. These enzymes contribute to flavor compound generation in dairy products by catalyzing not only the release of SCFAs, but also the synthesis of esters. These metabolites are responsible for piquant (SCFAs) and fruity (esters) flavors in goat?s milk cheeses. The aim of this study was to evaluate the esterolytic activities of ten LAB strains isolated from artisanal goat dairy products from Santiago del Estero. Esterolytic activity was determined in cell free extract (CFE) of Lactobacillus plantarum (UNSE66, UNSE230, UNSE287), L. bulgaricus (UNSE308, UNSE309), Pediococcus sp. (UNSE22, UNSE216, UNSE 253) and Streptococcus thermophilus (UNSE314, UNSE315) strains, using (α and β-naphthyl derivatives of fatty acids (α-, β-NA) of 2-12 carbon atoms (C2-12) as substrates. A unit of esterolytic activity (U) was defined as the amount of enzyme that released 1 µmol of α- or β-naphthol per minute. Specific esterolytic activity was defined as units per milligram of protein. Results showed the presence of esterolytic activity in the CFE of all the strains assayed on α- and β-NA of C2-C8, and α-NA of C10. Streptococcus thermophilus UNSE315 was the only strain displaying activity on α-NA C12. The highest activities were observed in lactobacilli, mean activities on α-NA C2 being 1.92 ± 1.10 U/mg and 1.19 ± 0.39 U/mg in L. plantarum and L.bulgaricus strains, respectively. Lower activities were observed on longer-chain substrates, a 10-fold lower activity (0.13 ± 0.10 U/mg) on α-NA C8 being detected in L. bulgaricus. In general, pediococci showed 2-fold higher activities compared to streptococci (0.43 ± 0.17 U/mg and 0.23 ± 0.02 U/mg on α-NA C2, respectively). The evaluated strains preferentially release fatty acids from 2 to 8 carbon atoms. These fatty acids, such as butyric and caprylic are responsible for piquant flavors in cheese. Therefore, the use of these strains could improve the organoleptic characteristics of goats milk cheeses.