Identificação de uma enzima agarolítica de microrganismo marinho associado a macroalga Gracilaria birdiae

Abstract

Seaweeds are organisms rich in biocomposites for vast industrial applications. Several researches are carried to promote the use of this biomass for the generation of new products and processes for the benefit of society. Agarases are enzymes that catalyze the degradation reaction of the agar, generating products primarily of cosmetic, pharmaceutical and food interest In this work, the microbiota sainity resistente of the Gracilaria birdiae macroalgae was studied and allowed to isolate an agarolytic bacterium (encoded GB002), which showed high growth in saline culture medium with 2.5% NaCl, 0.5% MgSO4.7H2O, KCl 0.1%, 0.01% CaCl2.2H2O, 0.01% K2HPO4, 0.002% FeSO4.7H2O, 0.1% yeast extract at 32 ° C, pH 7.0 and 0.1% agar as its sole source of carbon. Culture media with variations in carbon and organic nitrogen sources (commercial agar, peptone and biomass of Gracilaria birdiae) were tested and GB002 showed rapid growth and with a biomass accumulation in all medium. The maximum specific growth rate (μmax = 0.376 h-1) of GB002 was observed when G. birdiae was used as nutrients source. Combined with the growth, the study of agarase production was higher in the medium containing commercial agar as carbon source and peptone as a nitrogen source in 6 h culture (0.490 ± 0.090 U mL-1), however, the medium prepared from 1% of the fresh biomass of G. birdiae showed the highest microbial concentration of all studied media (1.82 x 109 CFU mL-1) and 95.9% of the maximum enzyme activity found in the previous medium. Growth in both culture media presented a low lag phase (<4 h) and the decline in cultures started around 24 h. A protein with approximate mass of 44 kDa was observed by 12.5% SDS-PAGE, and enzymatic activity was revealed by zymography. Based on the experiments, it was possible to produce a protein extract with 3.87 U mgP-1 agarolytic activity at 15.86 mgP mL-1 by discontinuous fermentation, which opens paths for the development of processes and products derived from the Gracilaria birdiae biomass.