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Biotechnological conversions of bio-diesel derived waste glycerol into added-value compounds by higher fungi: production of biomass, single cell oil and oxalic acid

Agricultural University of Athens, Department of Food Science and Technology, 75 Iera Odos, 11855 Athens, Greece
Industrial Crops and Products (Impact Factor: 2.84). 03/2010; DOI: 10.1016/j.indcrop.2009.12.011

ABSTRACT Waste bio-diesel derived glycerol was used as the sole carbon source by higher fungi; two Lentinula edodes strains were flask cultured in carbon-limited conditions and displayed satisfactory growth in media presenting weak agitation, pH 4.0 and temperature 25 °C. Maximum biomass of 5.2 g/l was produced. Mycelia were synthesized, containing around 0.1 g of fat per g of biomass, with linoleic acid (Δ9,12C18:2) being the principal cellular fatty acid produced. Two Aspergillus niger strains were grown in nitrogen-limited flask cultures with constant nitrogen and two different initial glycerol concentrations into the medium. In 250-ml flask cultures, large-sized pellets were developed, in contrast with the trials performed in 2-l flasks. Nitrogen limitation led to oxalic acid secretion and intra-cellular lipid accumulation; in any case, sequential production of lipid and oxalic acid was observed. Initially, nitrogen limitation led to lipid accumulation. Thereafter, accumulated lipid was re-consumed and oxalic acid, in significant quantities, was secreted into the medium. In large-sized pellets, higher quantities of intra-cellular total lipid and lower quantities of oxalic acid were produced and vice versa. Maximum quantities of oxalic acid up to 20.5–21.5 g/l and lipid up to 3.1–3.5 g/l (corresponding to 0.41–0.57 g of fat per g of biomass) were produced. Lipid was mainly composed of oleic (Δ9C18:1) and linoleic (Δ9,12C18:2) acids.

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