Inhibiting behaviour of lignin in fungi and yeast cultures (Aspergillus niger and Saccharomyces cerevisiae screenings)

In recent years, the exploitation of lignin as one of the most important Biorefinery products is being widely studied. Because of its complex structure and its high phenolic content, this lignocellulosic component results a promising source for several high value products. Many studies have dealt with the lignin application as antioxidant agent in different fields as additive in food packaging, in pharmaceutical and cosmetic formulations, or as ingredient for the so-called functional foods in human or animal feed. The structure and properties of lignin are highly dependent on the raw material from which is extracted, the used solvents, the process conditions and subsequent treatments used for its production; hence several studies should be performed to ensure the feasibility of this application. In the present work the antifungal and anti-fermentative effects of lignin were studied. Different fractionation processes were applied for lignin obtaining (autohydrolysis, organosolv fractionation with ethanol and acetic acid, and soda process) and the resulting samples were analyzed by different techniques (ATR-IR, TGA, RMN) and chemically characterized (chemical composition and total phenolic content) in order to determine their physicochemical properties. Several A. niger cultures were made in solid medium in order to evaluate the effect that lignin had on the fungi growth (inhibition and metabolites production). The anti-fermentative effect of lignin obtained by different methods was estimated from agar broth screenings with S. cerevisiae. The results showed that the level at which lignin affects the growth of both microorganisms depends on its composition and structure and, therefore, on the methodology used for its isolation.