Screening, purification and characterization of extracellular lipases from mangrove sediment yeasts

Abstract

Yeasts present in mangrove sediments were found to play an important role in detrital food web, nutrient cycling, decomposition and biodegradation. They produce hydrolytic enzymes and secondary metabolites which have formidable industrial, biotechnological and bioremediation properties. Since the mangrove sediments experience extreme environmental circumstances, the yeast and the enzymes produced from them can also withstand such utmost conditions. This makes mangrove sediment yeasts the best source for the production of industrially and biotechnologically important enzymes. Yeasts that can produce extracellular lipases were screened and isolated from the mangrove sediments of Kerala coast. Lipases were isolated and purified from two selected strains identified as Candida tropicalis (VPY3) and Diutina mesorugosa (VPY42). The final purification folds of C.tropicalis and D.mesorugosa lipases were calculated to be 5.6% and 4.6% and final specific activities were 2.643 U/mg and 2.662 U/mg respectively. The molecular weights of the purified lipases were estimated by SDS-PAGE to be ~50kDa for Candida tropicalis and ~59kDa for D.mesorugosa. The optimum incubation time, temperature and pH of VPY3 lipases for maximum activity were 30 minutes, 30⁰C and 6 while that for VPY42 were 20 minutes, 20⁰C and 5. Both the lipases were stable at wide range of temperatures, pH and in the presence of metal ions and organic solvents. The enzyme kinetics studies showed that the Km and Vmax values of VPY3 lipase were 0.32mM and 58.24U/mL/min and that for VPY42 lipase were 0.55mM and 178.36U/ml/min respectively. This indicates that lipases have high substrate affinity and can act as good biocatalysts. These interesting characteristics of purified lipases from mangrove sediment yeasts C.tropicalis and D.mesorugosa in the present study make them highly suitable for biotechnological and industrial applications.