Optimization and partial purification of a high-activity lipase synthesized by a newly isolated Acinetobacter from offshore waters of the Caspian Sea under solid-state fermentation

A new aerobic mesophilic bacterium was isolated from the southern coastal waters of the Caspian Sea which substantially produced an extracellular lipase in solid-state fermentation using milled coriander seeds (MCS) as support substrate. This bacterium was identified as a strain of genus Acinetobacter based on morphological and biochemical characterization and 16S rRNA gene sequence. The various medium components and culture parameters to achieve a more cost effective and economically viable bioprocess were screened and optimized using the Plackett-Burman and central composite designs. The highest lipase activity (20 480.2 U g(-1)) was achieved at optimum levels of predominant factors of MCS/yeast extract (4.0 w/w), olive oil concentration (30 g L-1), moisture content (65.0%), and agitation rate (180.0 rpm). The enzyme with molecular weight of 46 kDa was purified 26.9-fold to homogeneity by ammonium sulfate precipitation and phenyl-Sepharose hydrophobic interaction chromatography. The functional groups of the lipase were also assigned using Fourier transform-infrared spectroscopy.