Gene cloning, heterologous expression and biochemical characterization of a novel extracellular lipase from Rhizopus oryzae KU45

Background: Lipases secreted from various Rhizopus oryzae strains were previously expressed in Escherichia coli, Pichia pastoris, and Saccharomyces cerevisiae and was shown to have distinct activities in response to different temperatures, metal ions, organic solvents, and specific substrates. However, until now, no other research biochemically characterized the functions of extracellular pro-lipase in a novel Rhizopus oryzae KU45. Objectives: Characterization of a novel extracellular lipase from fungus R. oryzae KU45 after heterologous expression in E. coli BL21 (DE3) strain. Materials and Methods: An extracellular lipase producing fungus was isolated from a soil sample and identified as a strain of R. oryzae by partial 18S rRNA gene sequencing. It was named as R. oryzae KU45. The lipase gene of KU45 was cloned into pET-28a expression vector and expressed in E. coli as inclusion bodies. The recombinant lipase was purified, refolded and characterized. Results: The lipase exhibited maximum activity at 45ºC, at slightly alkaline pH. It showed a broad substrate specificity acting on p-nitrophenyl esters with C8-C16 acyl groups as substrates and, many of the organic solvents and metal ions tested did not have any adverse effects on the enzyme activity. Conclusions: High stability, broad substrate specificity and activity at mesophilic temperatures in the presence of organic solvents, and metal ions make the extracellular lipase of KU45 a candidate for various biotechnological applications