Production and extraction of extracellular lipase from the entomopathogenic fungus Isaria fumosoroseus (Cordycipitaceae; Hypocreales)

Abstract

Lipases are important cuticle degrading enzymes involved in the infection process of entomopathogens by hydrolysing the ester bonds of lipoproteins, fats and waxes present in the insect integument. Production of extracellular lipase by Isaria fumosoroseus (Cordycipitaceae; Hypocreales) isolate IF28.2 was investigated using different combinations of basal medium components. The effect of different vegetable oils added to a basal medium at different concentrations to improve enzyme production was evaluated. Maximum lipase activity (125.33±2.96 U/mL) as well as maximum biomass production (22.36±0.99 mg/mL) was observed for olive oil when used at a concentration of 2% (v/v) of the basal medium. In the presence of surfactants, the highest lipase activity occurred when SDS and Tween 80 were added at the time of fungal inoculation. SDS proved to be the best surfactant having 110.66±3.52 U/mL lipase activity. The effects of the divalent metal ions (iron and magnesium) on lipase activity were also studied. Iron inhibited, whereas magnesium slightly increased lipase activity. The optimum pH for lipase production was 5.7 while 32°C proved to be the best temperature for lipase production.

Keywords:

• Isaria fumosoroseus
• lipase
• vegetable oils
• temperature
• pH

Acknowledgements

This research was funded by grants from the National Basic Research Program (called 973 Program) (No. 2006CB102005) and Public sector specific research projects (No. 200803005).