Purification and characterization of a surfactant-compatible lipase from Aspergillus tamarii JGIF06 exhibiting energy-efficient removal of oil stains from polycotton fabric

Abstract

An extracellular lipase with 23,666.66 U/ml/min activity was produced by Aspergillus tamarii JGIF06 under submerged fermentation in mineral salt medium containing coconut oil (2.5 % v/v), tryptone (2 % w/v) and ammonium chloride (2 % w/v), with initial pH of 5 ± 0.2, incubated at 25 °C for 7 days on a rotary shaker at 120 rpm. A 7.9-fold increase in lipase-specific activity was recorded after purification by DEAE Sepharose ion exchange and Sephadex G200 column chromatography. The apparent molecular mass of this enzyme was revealed as 50 kDa by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The optimal lipase activity was recorded at pH 4 and 37 °C. The enzyme revealed broad specificity towards different vegetable oils. The K _m and V _max of the lipase on olive oil was found to be 330.4 mg and 53,690 U/ml/min, respectively. The lipase activity was stable in the presence of surfactants such as cetrimonium bromide, sodium dodecyl sulphate and Tween 80, and metal ions and reagents such as Ca²⁺, Ba²⁺ and 2-mercaptoethanol. However, the activity was greatly reduced in the presence of organic solvents such as chloroform. The stain removal potential of the crude lipase was determined on polycotton fabric pieces stained with peanut oil. Lipase added to cold water alone significantly enhanced the removal of stain by 152 %. The addition of lipase also improved the stain removal efficiency of a commercially available detergent in the presence of either cold (25 ± 2 °C) or hot (65 ± 2 °C) water. The current findings suggest the potentiality of this enzyme for energy-efficient biocatalytic application.

Keywords: Aspergillus tamarii; Lipase; Surfactant; Vegetable oil.

Fig. 1

a SDS-PAGE profile of lipase from A. tamarii JGIF06. 1 Protein marker. 2 Uninoculated medium. 3 Crude lipase extract. 4 Purified lipase. The molecular sizes of the marker proteins are shown on the left. b Zymography of purified lipase showing a band of lipolysis (indicated by arrow) on visualization of gel under 350 nm UV light

Fig. 2

a Effect of pH on lipase activity. b Effect of temperature on lipase activity. Data represent mean ± SD (n = 3); p < 0.05

Fig. 3

a Specificity of lipase towards different vegetable oils used as substrates. b Lineweaver–Burk plot using olive oil as substrate for the lipase. Data represent mean ± SD (n = 3); p < 0.05

Fig. 4

a Effect of surfactants on lipase activity. b Effect of metal salts and reagents on lipase activity. Data represent mean ± SD (n = 3); p < 0.05

Fig. 5

Oil-destaining efficiency of various lipolytic treatments on oil-stained fabric pieces. Data represent mean ± SD (n = 3); p < 0.05