Agroindustrial waste from the cuyo region revalorization: preliminary tests using solid state fermentation

Abstract

The agroindustrial activity of the Cuyo region is based mainly on the processing of two crops: the vine and the olive; and to a lesser extent fruits and vegetables. The wine industry and the olive oil industry generate large amounts of solid waste, such as grape marc, grape stalks and olive mark (OM). At present, the final disposal of these residues is difficult due to their high concentrations of phytotoxic substances, causing environmental problems if they accumulate in large quantities. Due to its chemical composition (carbohydrates, fiber, fats, proteins and mineral salts), agro-industrial residues are suitable substrates for biotechnological proceesing to obtain value-added products. The objective of this work was to carry out a preliminary study of the production of hydrolytic enzymes using Aspergillus niger in Solid State Fermentation (SSF) using solid regional wastes. The following residues were used: red grape marc (RGM), olive mark (OM) and mixture RGM-OM (50% w/w of each one). SSF were carried out in Petri´s dishes at 27°C, with solid medium initial moisture content of 60% w/w and an inoculum size of 1x107 spores*g dry-1 of A. niger. Two samples of culture were taken per day during one week for subsequent analytical determinations. The enzymatic activities that were measured in the aqueous extracts of SSF were: α-L-arabinofuranosidase (α-L-arf), α-L-rhamnosidases (α-L-rha), exopolygalacturonase (exo-PG), laccase (lac) and lignin peroxidase (LiP). The maximum enzymatic activity values were obtained for α-L-arf and exo-PG. The maximum activities for both enzymes were: 2.62U/g for α-L-arf, at 58 hours of cultivation and 4.53U/g for exo-PG at 70 hours, in SSF of RGM-OM. As for lac and α-L-rha activities, lower values were obtained. No significant amounts of LiP activity were determined. The results obtained indicate that it is of interest to optimize the SSF tests with the mixture of the two solid substrates to maximize the values of the enzymatic complex, investigating the culture conditions and nutrient additions.