Purification and characterization of alkaline pectin lyase from a newly isolated Bacillus clausii and its application in elicitation of plant disease resistance.

Alkaline pectin lyase (PNL) shows potential as a biological control agent against several plant diseases. We isolated and characterized a new Bacillus clausii strain that can produce 4,180 U/g of PNL using sugar beet pulp as a carbon source and inducer. The PNL was purified to apparent homogeneity using ultrafiltration, ammonium sulfate fractionation, DEAE Sepharose Fast Flow, and Sephadex G-75 gel filtration. The purified PNL was found to be a monomeric protein with a molecular weight of 35 kDa, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). It demonstrated optimal activity with K(m) of 0.87 mg/ml at pH 10.0 and 60 °C. The enzyme is stable in the pH range of 8.0-10.0 and temperature ≤40 °C. Ca(2+) was found to stimulate the enzymatic activity of the PNL by up to 410 %. Mass spectrometric results gave 38 % match coverage with pectate lyase from B. clausii KSM-K16 (gi|56961845). The PNL was found to elicit disease resistance in cucumber seedlings, suggesting that it may have applications in biocontrol and sustainable agriculture.