Mortierella Ramanniana Lipid Fermentation Wastewater as an Innovative Maceration Liquid Medium for Sustainable Solid-State Cultivation of Higher Fungi

Mortierella ramanniana was flask cultured with glycerol (≈ 35 g/L) being employed as substrate, under carbon and nitrogen limitation. Under carbon limitation, glycerol was rapidly consumed and total dry cell weight (X, g/L) ≈ 16 g/L containing lipid ≈ 24% w/w was synthesized. Lipids contained the important poly-unsaturated fatty acid γ-linolenic (GLA) to concentrations 9–13% w/w, with GLA_max achieved ≈ 430 mg/L. Under nitrogen limitation glycerol was slowly assimilated, lower X values (up to 12 g/L) containing higher lipid quantities (up to 45% in X) were noted and lipids contained GLA to concentrations = 6–9% w/w (GLA_max achieved was ≈ 350 mg/L). Lipid fermentation wastewater (LFW) was used as maceration water for mushrooms’ solid-state fermentation. Substrates were supplemented with coffee and olive crop residues, along with soybean flour and wheat bran to achieve a low (15–20) and a high (40–60) C/N ratio. Mushrooms were studied regarding mycelial growth rates, biomass production, total phenolic compounds (TPC) consumption, enzymes (endoglucanase, laccase, manganese-dependent peroxidase/MnP) biosynthesis and exopolysaccharides (EPS) production. In high C/N, fungi exhibited the highest growth rates. Addition of LFW influenced biomass production, with the most positive effects being observed in Lentinula edodes and Pleurotus ostreatus. Substrate composition and not LFW addition impacted EPS production, while C/N had various effects on it. LFW increased TPC consumption, which was particularly evident in P. ostreatus. Low C/N induced hydrolytic and ligninolytic enzymes. LFW favored laccase production, while there was no specific pattern in endoglucanase and MnP activity. Substrates of high C/N ratio were further evaluated for carposome production, where the yield and biological efficiency-BE % were calculated. This study demonstrates the feasibility of utilizing LFW in SSF for the conversion of low-value waste into biomass, important metabolites and value-added food products.