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The phyL gene encoding phytase from the industrial strain Bacillus licheniformis ATCC 14580 (PhyL) was cloned, sequenced, and overexpressed in Escherichia coli. Biochemical characterization demonstrated that the recombinant enzyme has an apparent molecular weight of nearly 42 kDa. Interestingly, this enzyme was optimally active at 70-75 °C and pH 6.5-7.0. This enzyme is distinguishable by the fact that it preserved more than 40 % of its activity at wide range of temperatures from 4 to 85 °C. This new phytase displayed also a high specific activity of 316 U/mg. For its maximal activity and thermostability, this biocatalyst required only 0.6 mM of Ca(2+) ion and exhibited high catalytic efficiency of 8.3 s(-1) μM(-1) towards phytic acid.

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Phytases catalyze the hydrolysis of phytic acid in a stepwise manner to lower inositol phosphates, myo-inositol (having important role in metabolism and signal transduction pathways), and inorganic phosphate. These enzymes have been widely used in animal feed in order to improve phosphorus nutrition and to decrease pollution in animal waste. Compared to previously described phytases, the phytase (PhyL) from Bacillus licheniformis ATCC 14580 has attractive biochemical properties which can increase the profitability of several biotechnological procedures (animal nutrition, humain health…etc). Due to its amino acid sequence with critical substitutions, the PhyL could be a model to enhance other phytases features, in terms of thermal stability and high activity. Otherwise, an engineered PhyL, with low pH optimum, will represent a challenge within the class of β- propeller phytases.

The phytotoxicity potential of phosphate laundries wastewater (PLW) is assessed. Likewise, the assays of biotreatment of the PLW by microbial detoxification are investigated. Chemical characterization results show that PLW are alkaline, saline, highly turbid, and rich in suspended matter and total solids. PLW samples are loaded with potentially toxic metals, presented in decreasing order as follows: calcium (1230 mg L−1), potassium (1032 mg L−1), iron (275.45 mg L−1), lead (1.64 mg L−1), zinc (1.12 mg L−1), copper (1.04 mg L−1), and cadmium (1.03 mg L−1). Besides, PLW exhibits high phytotoxicity values for Raphanus sativus, Medicago sativa, and Sorghum bicolor seeds germination. The microbiological enumeration reveals considerable autochthonous microflora. Biotreatment includes five selected native strains (Se, S16, S19, S20, and S29) used as a tool of PLW detoxification. The strains tested manifest a bioprocessing performance according to the following decreasing order: S29 > S16 > S20 > S19 > Se. The biotreated phosphate laundries wastewater (BTPLW) achieves a noticeable reduction of toxicity. Indeed, analysis of the correlation matrix between the potentially toxic metal content and the germination index (GI) values shows significant correlations (p ≤ 0.01).