INACTIVATION OF THE GLUTAMATE DEHYDROGENASE ACTIVITY IN Lactobacillus casei AND ITS EFFECT ON GROWTH AND FLAVOR

ZULAJAN F; ALARCON S; CH. MAGNI,

rosario

Congreso; SAIB 2014; 2014

SAIB

Lactobacillus casei is one of the strains commonly used in adjunct cultures for the cheese ripening contributing to the final organoleptic characteristics. The amino acids (AA) catabolism contributes to the flavor production being the glutamate a key compound in the recycling and conversion of α-ketoacids. From these compounds, the AA are sources of organic acids, alcohols, aldehydes, ketones and esters which give food flavor. The α-ketoglutarate regeneration by glutamate dehydrogenase (GDH) has been reported be a desired activity of adjunct cultures. We evaluated the role of GDH in the flavor generation from AA metabolism, and the survival and growth on different carbon and nitrogen sources. For that, we made a mutant strain of Lb. casei with the gdh gene disrupted and its phenotype was compared with that of the wild type (WT) strain. The growth of the mutant and WT strain was evaluated in MRS medium using different carbon and nitrogen sources. The aroma production was assessed in resting cells through the solid-phase microextraction (SPME) system followed by gas chromatographic separation coupled to a mass spectrometer as detector (GC-MS). The relative AT activities of the cell-free extracts was also evaluated. This study provides further evidence of the role and importance of GDH for AA catabolism and survival of Lb casei under different carbon and nitrogen sources.