An Organic Solvent-Tolerant Lipase with Both Hydrolytic and Synthetic Activities from the Oleaginous Fungus Mortierella echinosphaera.

Lipase enzymes of the oleaginous fungal group Mortierella are rarely studied. However, considering that most commercial lipases are derived from filamentous fungal sources, their investigation can contribute to the cost-effective development of new biotechnological processes. Here, an extracellular lipase with a molecular mass of 30 kDa was isolated from Mortierella echinosphaera CBS 575.75 and characterized. The purified lipase exhibited an optimal p-nitrophenyl palmitate (pNPP)-hydrolyzing activity at 25 °C and pH 6.6-7.0 and proved to be highly stable at temperatures up to 40 °C and under broad pH conditions. The enzyme was active under low temperatures, retaining 32.5% of its activity at 10 °C, and was significantly stable in polar and non-polar organic solvents. The K(m), V(max), and k(cat) for pNPP were 0.336 mM, 30.4 μM/min, and 45.7 1/min for pNPP and 0.333 mM, 36.9 μM/min, and 55.6 1/min for pNP-decanoate, respectively. The pNPP hydrolysis was inhibited by Hg(2+), N-bromosuccinimide, and sodium dodecyl sulfate, while ethylenediaminetetraacetic acid and metal ions, such as Ca(2+), Mg(2+), Na⁺, and K⁺ enhanced the activity. The purified lipase had non-regioselective activity and wide substrate specificity, showing a clear preference for medium-chained p-nitrophenyl esters. Besides its good transesterification activity, the enzyme appeared as a suitable biocatalyst to operate selective esterification reactions to long-chained alkyl esters. Adsorption to Accurel MP1000 improved the storage stability of the enzyme at 5 °C. The immobilized lipase displayed tolerance to a non-aqueous environment and was reusable for up to five cycles without significant loss in its synthetic and hydrolytic activities. These findings confirm the applicability of both the free and the immobilized enzyme preparations in future research.