Novel routes for valorisation of grape pomace through the production of bioactives by Aspergillus niger

Abstract

Abstract: Grape pomace is an abundant winery by-product produced worldwide, which contains a high concentration of polyphenols trapped in cell wall fibers. The fungus tannase enzyme finds many applications in the industry, but its use is currently limited. This is due to its high production cost derived from tannic acid, which is the typical inductor of tannase enzyme by Aspergillus species. Therefore, assessment of natural tannin sources as inductors is a strategy to overcome this limitation. We propose here to employ the red grape pomace, which is a rich source of tannins and polyphenols. We found that, although grape pomace is not able to induce tannase by itself, it is a useful complement for tannic acid induction, reducing the concentration of tannic acid necessary to achieve maximum levels of tannase induction, which ranged between 3.0 and 4.5 U/mL. We also explored the potential usage of this biomass to induce other relevant industrial enzymes and quantified the recovery of gallic acid from grape pomace by the fungus fermentation; finding new routes for this by-product valorisation.