Relationships between lipases and lipids in mycelia of two Mucor strains

Strains of filamentous fungi Mucor circinelloides and M. racemosus (from pure culture collection of the Institute of Technical Biochemistry of TU of Lodz), known as efficient producers of intracellular lipases [Prog Biotechnol 1999;17:221; J Mol Catal B Enzym 2001;11:1043], form also numerous lipid bodies, which are rich in unsaturated fatty acids, in optimum conditions for lipases synthesis. The simultaneous production of lipase preparations and microbial lipids would improve the overall economics of bioprocess. To find if this is feasible, the dependence of lipid accumulation in biomass of Mucor strains on concentration of corn steep liquor (CSL) and plant oil, and glucose was determined. The studies included: assays of lipolytic and esterolytic activities of intra- and extracellular lipases, estimation of amounts of intracellular lipids and membrane-bound lipase (MBL) preparations, and characterization of lipid composition. Lipids and their fractions derived by solid phase extraction (SPE) were separated by TLC. Contents of free fatty acids (FFA), phospholipids (PL) and carotenoids (Car) and fatty acid profiles were also assayed. It was found that: (1) lipid content amounted to 60–70% of biomass d.w.; (2) both TAGs (olive oil) and CSL stimulated an overproduction of intracellular lipase and lipids, but activity of the former was decreased by glucose; (3) in the presence of TAGs and/or CSL the lipids contained more FFA and linoleic acid (C18:2), and significantly less saturated FA (C16:0 and C18:0) than lipids accumulated in glucose-containing medium; (4) both CSL and glucose enhanced PL and Car content in lipids (amount of the latter exceeded 90 mg per 100 g of total lipids (TL) for M. circinelloides); (5) the presence of PL in MBL preparations was crucial for their lipolytic activity.