Harnessing Winery and Distillery By-Products with Aspergillus oryzae: Potential for development of innovative fungi-based fermented food and feed

Winery and distillery by-products, such as grape marc (GM), pre-distillation lees (PRE), and post-distillation lees (POST), pose environmental challenges due to their high chemical oxygen demand (COD). However, these by-products represent an underutilized resource with significant potential to contribute to sustainability. This study investigates the biovalorization of these by-products through the cultivation of the edible filamentous fungus Aspergillus oryzae to produce protein-rich fungal biomass via aerobic submerged fermentation. Hydrothermally pretreated and filtered substrates were used as liquid cultivation media at concentrations of 4% GM (w/v), 50% PRE (v/v), and 10% POST (v/v). The effect of these substrates on fungal growth was assessed by analyzing protein, amino acids (AAs), mineral, and polyphenol content, alongside COD. The results showed that A. oryzae biomass had enhanced protein content (29.4–55.6%), approximately twice that of the substrates, following the order 50% PRE > 4% GM > 10% POST. Total AAs ranged from 10.9% to 28.5% dry weight, with leucine and lysine as the dominant essential AAs. The fungal biomass was rich in minerals such as phosphorus (132.4–175.4 mg/100 g), magnesium (13.4–14.1 mg/100 g), and iron (3.76–4.57 mg/100 g), and contained total polyphenols ranging from 7.54 to 36.2 mg gallic acid equivalent/g biomass. Additionally, the process achieved a COD reduction of 46–79%, mitigating the environmental impact of these by-products. This approach highlights the potential of transforming these by-products into high-quality protein, providing new opportunities for innovative applications in food and feed production, while promoting sustainable food systems within circular bioeconomy framework.