Purification and characterization of a serine protease secreted by Brevibacillus sp. KH3 for reducing waste activated sludge and biofilm formation

► The 40-kDa protease which is related to the reduction of waste activated sludge was purified and characterized. ► The protease is a serine-type one containing metal ions. ► The protease contains calcium ions required for the enzyme activity. ► Biofilm formation was inhibited by the protease.