Thermostable, alkaline and detergent-tolerant lipase from a newly isolated thermophilic Bacillus stearothermophilus.

Lipases are the enzymes of choice for laundry detergent industries, owing to their triglyceride removing ability from the soiled fabric, which eventually reduces the usage of phosphate-based chemical cleansers in the detergent formulation. In this study, a novel thermo-alkaline lipase-producing strain identified as Bacillus stearothermophilus was isolated from the soil samples of olive oil mill. Enhanced lipase production was observed at 55°C, pH 11 and after 48 h of incubation. Among the substrates tested, xylose (a carbon source), peptone (a nitrogen source) and olive oil at a concentration of 1% were suitable substrates for enhancing lipase production. MgSO4 and Tween-80 were suitable substrates for maximizing lipase production. The enzyme was purified to homogeneity by a single CM-Sephadex column chromatography and revealed molecular mass of 67 kDa. The enzyme (BL1) was active over a wide range of pH from 9.0 to 13.0, with an optimum at pH 11.0, exhibited maximal activity at 55°C and retained more than 70% of its activity after incubation at 70°C or pH 13 for 0.5 h or 24 h, respectively. The enzyme hydrolyzed both short and long-chain triacylglycerols at comparable rates. BL1 was studied in a preliminary evaluation for use in detergent formulation solutions. This novel lipase showed extreme stability towards non-ionic and anionic surfactants after pre-incubation for 1 h at 40°C, and good stability towards oxidizing agents. Additionally, the enzyme showed excellent stability and compatibility with various commercial detergents, suggesting its potential as an additive in detergent formulations.

Purification and characterization of a phospholipase A2-IIA from common stingray (Dasyatis pastinaca) intestine.

A phospholipase A2 belonging to IIA group secretory PLA2 was isolated and purified to homogeneity from the intestine of common stingray (Dasyatis pastinaca) using acidic treatment (pH 1.5) and ammonium sulphate precipitation methods combined with single-column ion-exchange chromatography. The purified enzyme was found to be a glycosylated monomeric protein with a molecular mass of about 14 kDa. The stingray sPLA2-IIA had optimum activity at 45°C, unlike known mammalian PLA2-IIAs, which show optimum activity at 37°C. The purified enzyme exhibited a specific activity of 290 U/mg at optimal conditions (pH 9.5 and 45°C) in the presence of 6 mM NaDC and 8 mM CaCl2 with egg yolk as substrate. The NH2-terminal sequence of the enzyme and some protein fragments obtained from its tryptic digestion were also determined. All sequences obtained were similar to those of sPLA2-IIA. The enzyme also showed good stability in the presence of organic solvents, acidic and alkaline pH media and high temperature conditions. Thus, the purified enzyme exhibited a number of unique and promising properties, making it a potential possible candidate for future applications in the treatment of phospholipid-rich industrial effluents and synthesis of useful preparations for the food production and processing industry.