Abstract
Mycelium-bound lipase (MBL), from a locally isolated Geotrichum candidum strain, was produced and characterized as a natural immobilized lipase. A time course study of its lipolytic activity in 1 L liquid broth revealed the maximum MBL activity at 4 h for mycelium cells harvested after 54 h. The yield and specific activity of MBL were 3.87 g/L dry weight and 508.33 U/g protein, respectively, while less than 0.2 U/mL lipase activity was detected in the culture supernatant. Prolonged incubation caused release of the bound lipase into the growth medium. The growth pattern of G. candidum, and production and properties of MBL were not affected by the scale. The stability of mycelia harboring lipase (MBL), harvested and lyophilized after 54 h, studied at 4 °C depicted a loss of 4.3% and 30% in MBL activity after 1 and 8 months, while the activity of free lipase was totally lost after 14 days of storage. The MBL from G. candidum displayed high substrate selectivity for unsaturated fatty acids containing a cis-9 double bond, even in crude form. This unique specificity of MBL could be a direct, simple and inexpensive way in the fats and oil industry for the selective hydrolysis or transesterification of cis-9 fatty acid residues in natural triacylglycerols.
Highlights
The current demands of the world’s biotechnological industries are enhancement in enzyme productivity and increasing their shelf life
Dry mycelium of Rhizopus oryzae as immobilized biocatalyst has been successfully applied for ester production [2]. the reactivity and stability of mycelium-bound carboxylesterase from lyophilized cells of Aspergillus oryzea has been explored in organic solvents [3]
It was indicated that the maximum yield of FFA, lipase activity and cell mass during growth of the G. candidum strain under study in the presence of palm olein were achieved at different incubation times, i.e., 48, 54 and 96 h, respectively [15]
Summary
The current demands of the world’s biotechnological industries are enhancement in enzyme productivity and increasing their shelf life. Fungal mycelia may be used as a direct source of the enzyme thereby eliminating the need for isolation, extraction, purification and external immobilization procedures in cases where the lipases are naturally bound to the cell wall. In view of the many advantages offered by natural immobilised enzymes, some works have been conducted by this laboratory using naturally immobilised lipases Those studies include the production and properties of Mycelium-bound lipase (MBL) from G. candidum [6], A. flavus [7,8] and R. miehei [9] and their applications in the modification (acidolysis) of several vegetable oils [10], and transesterification of palm kernel olein and anhydrous milk fat mixtures for the preparation of ice cream emulsions [11]. G. candidum, isolated earlier from local soil, and study its properties and the potential applications of the enzyme produced
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