Bamboo charcoal enhances cellulase and urease activities during chicken manure composting:Roles of the bacterial community and metabolic functions

Microbial enzymes are crucial for material biotransformation during the composting process.In this study,we investigated the effects of adding bamboo charcoal(BC)(i.e.,at 5%,10%,and 20%corresponding to BC5,BC10,and BC20,respectively)on the enzyme activity levels during chicken manure composting.The results showed that BC10 could increase the cellulose and urease activities by 56%and 96%,respectively.The bacterial community structure in BC10 differed from those in the other treatments,and Luteivirga,Lactobacillus,Paenalcaligenes,Ulvibacter,Bacillus,Facklamia,Pelagibacterium,Sporosarcina,Cellvibrio,and Corynebacterium had the most important roles in composting.Compared with other treatments,BC10 significantly enhanced the average rates of degradation of carbohydrates(Dxylose(40%)andα-D-lactose(44%))and amino acids(L-arginine(16%),L-asparagine(14%),and L-threonine(52%)).We also explored the associations among the bacterial community and their metabolic functions with the changes in the activities of enzymes.Network analysis demonstrated that BC10 altered the co-occurrence patterns of the bacterial communities,where Ulvibacter and class Bacilli were the keystone bacterial taxa with high capacities for degrading carbon source,and they were related to increases in the activities of cellulase and urease,respectively.The results obtained in this study may help to further enhance the efficiency of composting.

Methanation and chemolitrophic nitrogen removal by an anaerobic membrane bioreactor coupled partial nitrification and Anammox

An AnMBR-PN/A system was developed for mainstream sewage treatment.To verify the efficient methanation and subsequent chemolitrophic nitrogen removal,a long-term experiment and analysis of microbial activity were carried out.AnMBR performance was less affected by the change of hydraulic retention time(HRT),which could provide a stable influent for subsequent PN/A units.The COD removal efficiency of AnMBR was>93%during the experiment,85.5%of COD could be recovered in form of CH4.With the HRT of PN/A being shortened from 10 to 6 h,nitrogen removal efficiency(NRE)of PN/A increased from 60.5%to 80.4%,but decreased to 68.8%when the HRTPN/A further decreased to 4 h.Microbial analysis revealed that the highest specific ammonia oxidation activity(SAOA)and the ratio of SAOA to specific nitrate oxidation activity(SNOA)provide stable NO_(2)^(−)-N/NH_(4)^(+)-N for anammox,and anammox bacteria(mainly identified as Candidatus Brocadia)enriched at the bottom of Anammox-UASB might play an important role in nitrogen removal.In addition,the decrease of COD in Anammox-UASB indicated partial denitrification occurred,which jointly promoted nitrogen removal with anammox.