Solid-state Fermentation with Aspergillus niger Strains Improves the Nutritional Composition of Grape Seed, Cherry Kernel, and Maize Seed Mixture

The nutritional composition of fermented grape seed, cherry kernel, and maize seed mixture (GCM) with Aspergillus niger strains was investigated in this study. The fermentation substrate was prepared by mixing 20 g of maize seed, 40 g of grape seed, and 40 g of cherry kernel. A mixture of the different A. niger strains (ATCC 200344, 200345, 201572, 52172) was used in this study. The nutrient salt was added to the substrate and mixed. The mixture was sterilized at 121 °C for 15 min using an autoclave. Each A. niger suspension containing 106 spores per ml was prepared and inoculated into the sterilized substrate. The substrates were incubated at 30 °C for seven days. Crude protein, crude ash, ether extract, and crude fiber were analyzed in the unfermented and fermented substrates. Nitrogen-free extract was estimated by subtracting the percentages of crude protein, ether extract, crude ash, and crude fiber from 100%. The crude protein content of GCM was increased (P<0.001) after solid-state fermentation with A. niger. Solid-state fermentation also increased (P<0.001) the ether extract content of GCM. In addition, fermented GCM had higher (P=0.001) crude ash content than unfermented GCM. However, crude fiber content of GCM was reduced (P<0.001) by solid-state fermentation. Similarly, A. niger decreased (P<0.001) the nitrogen-free extract in GCM. The results showed that solid-state fermentation with A. niger improved the nutritional quality of GCM.