Study On Enzymes Production Of Hydrolytic Bacteria Cultured In Residual Sludge

Hydrolysis pretreatment of residual sludge by enzyme is an efficient method which can improve the sludge hydrolysis.However,because of the normal method of enzyme production is highly cost,as while as enzyme being added continuously,the application of enzyme in sludge pretreatment was astricted.In order to get cheaper enzymes which could be used into the residual sludge pretreatment,the enzyme production ability of Bacillus licheniformis and Bacillus cereus was studied when both of them cultured in the residual sludge as medium.The optimal initial conditions of enzyme production such as the pH,the ratio of compound bacteria and the amount of mixed bacteria inoculated in residual sludge were studied.The effects of high pressure and metal ions on enzyme production processing were discussed,too.The main conclusions are as follows:?1?In the enzyme producing process of Bacillus licheniformis and Bacillus cereus cultured in sterilization residual sludge,the optimal conditions of enzyme production were determined,which the ratio of compound bacterium of Bacillus licheniformis and Bacillus cereus was 2:1,the initial pH was 8,and the inoculum amount of mixed bacteria was 30%?pure bacteria liquid volume/sludge volume?.?2?Compared with cultured in sterilization residual sludge,the compound bacteria could produce more enzymes.But when cultured in sludge supernatant treated with high-pressure,they produced enzymes the most.The protease activity and the amylase activity were 252.31±1.40 U/mL the maximum and 266.86±8.40 U/mL the maximum,respectively.In the process of enzymes production of culturing with the sterilization residual sludge and the residual sludge treated with high-pressure,more humic acid and fulvic acid were dissolved,which might decrease the enzymes activities in the later stage.?3?The protease activity of sample with 0.03mol/LCa²⁺increased rapidly,up to246.14?9.09 U/mL the maximum on the 1st day,then it continued to rise and reached to340.07?5.87 U/mL the maximum on the 7th day.Compared with the blank sample,the protease activity increased 53.94%the maximum.The amylase activity of sample with0.03mol/LCa²⁺was 351.02?12.39 U/mL the maximum,which increased 51.93%compared with the blank sample.0.03mol/LCa²⁺could improve the enzyme production of hydrolytic bacteria when it cultured in sterilization residual sludge.Mg²⁺could not improve the enzyme production,but could maintain the stability of the enzyme activity.Proper amount of metal ions could enhance the enzyme production of hydrolysis bacteria cultured in the sterilization residual sludge,maintain the stability of enzyme activity,and promote sludge hydrolysis.?4?There was a significant positive relation between the Bacillus and the enzymes,and the Bacillus still was the dominant bacterium throughout the culturing process.Some dominant bacteria which related to sludge hydrolysis and enzyme production such as Lysobacter appeared in 0.03 mol/LCa²⁺sample with the culturing continued.And the Ca²⁺concentration was positively related to Bacillus,protease activity,amylase activity,SCOD,pH and ammonia nitrogen.It demonstrated that Ca²⁺could induce the changing of microbial community structure of residual sludge,and then improved the enzymes production of hydrolysis bacteria,while metabolic and enzyme of hydrolysis bacteria in residual sludge could also improve the sludge hydrolysis simultaneously.