Heterologous Expression of Gene Encoded Thermostable Lipase and Lipolytic Activity

Response Surface Methodology for Optimization Membrane Disruption Using Thermolysis in Lipase Lk2 and Lk3

Lk2 and Lk3 were thermostable recombinant lipase and highly expressed in Escherichia coli BL21 (DE3). However, Lk2 and Lk3 accumulated as an inclusion body. To further characterize both recombinant lipases, the soluble enzyme must be obtained first. This study aimed to optimize the disruption of the cell membrane in order to obtain soluble and active lipases. The effects of temperature lysis, pH, and SDS concentration on lipolytic activity Lk2 and Lk3 were investigated using a three-factor Box-Behnken design response surface methods. The optimum condition for the temperature variables at 50°C, pH 8, and 0.34% SDS which gave a lipolytic activity of 0.9 U for Lk2. Meanwhile, Lk3 lipolytic activity of 0.9 U obtained at the temperature of 50°C, pH 8, and 0.1% SDS. This result showed efficient one-step membrane disruption methods using thermolysis with addition of a low concentration of detergent at pH 8. The methods used were effective and applicable in the production of active and soluble thermostable recombinant lipase.

Effect of mutation at oxyanion hole residu (H110F) on activity of Lk4 lipase

Mutant of lipase at oxyanion hole (H110 F) was constructed. The gene was highly expressed in Eschericia coli BL21 (DE3) and the recombinant protein was purified using Ni-NTA affinity chromatography. The activity of mutant enzyme was significantly increased compared to that the wild type. Further comparison showed that both of the enzymes exhibited same optimum pH and temperature, and showed highest lipolytic activity on pNP-decanoate (C10). The wild type appeared lost of activity on C14 and C16 substrates meanwhile the mutant still showed activity up to 20 %. In the presence of non polar organic solvent such as n-hexane, the wild type became inactive enzyme meanwhile the mutant still remained 50 % of its activity. The results suggested that mutation at oxyanion hole (H110 F) caused enzyme-substrate interaction change resulting on elevation of activity, better activity toward longer carbon chain substrate and improving the activity in the present of non polar organic solvent.