Fungos associados à macroalgas tropicais e antárticas: taxonomia, diversidade e utilização em processos para produção de bioetanol de terceira geração

Abstract

ABSTRACT The depletion of fossil fuel reserves, oil price instability and increasing environmental and political pressures have stimulated the use of fuels produced from renewable biomass. In this context, the use of biomass of macroalgae for bioethanol production has shown promise because of its sustainability and renewable character. In view of this panorama, the aims of this study wereto isolate and identify fungi associated with tropical and Antarctic macroalgae and evaluate the potential of these fungi as the ability to hydrolyze the algal biomass. From the seaweed Kappaphycus alvarezii were obtained 99 filamentous fungi and from Antarctic macroalgae were obtained 19 filamentous fungi and 35 yeasts. After the molecular identification, the genera obtained most frequently were Cladosporium in K. alvarezii and Metschnikowia in Antarctic macroalgae. All fungi were evaluated for carragenolytic capability.The colorimetric test plate demonstrated that a significant proportion of filamentous fungi (71%) was able to hydrolyze carrageenan. Enzymatic hydrolysis of carrageenan under the conditions evaluated showed maximum value of 17 U/ml from the growth of Penicillium chrysogenum UFMGCB10066 in submerged fermentation. From the central composite design was possible to determine an optimum range of cultivation for the solid-state fermentation of the fungus and the optimal point of the model adjusted for all predictors occurred in approximately 9 days: 10.8 ° C and 77.8% humidity. Pretreatment with citric acid and subsequent enzymatic hydrolysis of Kappaphycus alvarezii was not efficient when compared to other jobs. The final yield was 9.9 g/L. This result shows that would be required to optimize other parameters for improved enzymatic hydrolysis of algal biomass by this fungus. Many studies havecharacterized the carragenolytic activity of marine bacteria; However, this study demonstrates that algae are a source of a wide variety of fungus capable of hydrolyzing the constituents of the walls of macroalgae. The unique and specifics biochemical characteristicsof the marine enzymes, as well as the growing interest in biotechnological applications, especially in the biofuel and pharmaceutical industries, shows the enormous potential of fungi associated with algae. The fact of the discovery of filamentous fungi capable of secreting carragenase opens a new perspective for the application of these fungi in the third-generation ethanol production.