Proteolytic activity in stored aerobic granular sludge and structural integrity

Area of Science:

• Microbiology
• Environmental Science
• Biotechnology

Background:

• Aerobic granules are crucial in wastewater treatment but lose stability during storage.
• The exact mechanisms behind this stability loss require further elucidation.

Purpose of the Study:

• To identify the primary cause of aerobic granule instability during storage.
• To characterize the microbial communities and enzymatic activities involved in granule degradation.

Main Methods:

• Analysis of extracellular protein quantities and protease enzyme activities in stored granules.
• Isolation and characterization of proteolytic bacteria using 16S rDNA sequencing.
• Microscopic examination of granule core structures and microbial distribution.

Main Results:

• Extracellular protein content decreased significantly, while protease activity increased in stored granule cores.
• Proteolytic bacteria, including Pseudomonas, Raoultella, and Bacillus genera, were identified.
• High proteolytic activity was observed in Pseudomonas aeruginosa strains within the granule core, near anaerobic bacteria.

Conclusions:

• Intracellular protein hydrolysis by bacterial proteases is the main cause of aerobic granule instability.
• Degraded proteins serve as nutrients for anaerobic bacteria, leading to granule digestion.
• Understanding these microbial interactions is key to preserving granule stability.