Valorisation of canning industry wastes for microbial lipid production by solid-state fermentation using Aspergillus oryzae CECT 2094

The fishing, canning, and aquaculture industries generate large volumes of by-products that are often discarded each year. This work explored the biotechnological valorisation of six by-products through solid-state fermentation (SSF). Specifically, mussel wastes (epibiota and broken viands and breeds), tuna wastes (central spine and viscera), and seaweed residues ( Ulva rigida and Saccharina latissima ) were employed as substrates for microbial lipid production using Aspergillus oryzae CECT 2094. The fungus grew successfully on all tested substrates, achieving increases in lipid content above 20% in most cases, with the exception of seaweed residues. After fermentation, significant increases in fatty acid methyl esters (FAME) were observed, with palmitic, stearic, and palmitoleic acids among the most abundant. Tuna central spine was particularly noteworthy, showing an average 3.5-fold increase in final FAME content, equivalent to 300 mg/g lipids increase compared to the raw biomass. Fermented mussel substrates also demonstrated nutritionally valuable profiles, achieving Omega-6/Omega-3 ratios between 1:1 and 5:1, ranges considered beneficial for human health. These findings highlight the potential of A. oryzae in SSF processes to convert marine industry by-products into microbial lipids. This approach supports circular economy strategies and aligns with the sustainability goals of the 2030 Agenda. • Marine by-products can be valorised via SSF using Aspergillus oryzae . • SSF significantly increases lipid content in mussel and tuna by-products. • Tuna spine lipids could be suitable for biodiesel; mussel lipids for food use. • Fatty acid profiles enhance nutritional value and industrial applicability. • This study expands SSF beyond lignocellulosic feedstocks using marine wastes.