Purification of a Thermostable Lipase Geobacillus thermodenitrificans nr68 (Lip.nr-68) with Potential for Enzymatic Deinking

Lipase from Geobacillus thermodenitrificans nr68 (Lip.nr-68) has shown great enzymatic bio-deinking activity towards a laser jet printed paper with deinkability brightness test of 55%, a value that was slightly lower than the value showed by a commercial lipase from Sigma (63%). In regards of this quality, Lip.nr-68 was purified and characterized to obtain the pure biological characteristic of this catalyst. Airlift fermenter system was used with optimum parameters of 65°C, pH of 6.8, and air flow rate of 1.00 L/min and inoculum size at 7.0% (v/v) in a cultivation medium containing; glucose of 1.25% (w/v); yeast extract of 1.25% (w/v); NaCl 0.75% (w/v) and olive oil of 0.10% (v/v) for 24 hours. The extracted extracellular crude lipase was purified to homogeneity by using four-step procedures: acetone precipitation, Sephadex G-100 filtration chromatography and twice of DEAE Sefarose CL-6B anion exchange chromatography by 22.1 times with a final yield of 25%. The molecular weight of the purified enzyme was estimated to be 33.5 kDa after SDS-PAGE analysis.