Comparison of protein extraction methods from excess activated sludge.

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Excess activated sludge poses a significant disposal challenge.
• Protein recovery from sludge offers a sustainable resource utilization pathway.
• Optimizing protein extraction methods is crucial for economic viability and environmental benefit.

Purpose of the Study:

• To compare the efficacy of various chemical, enzymatic, and assisted enzymatic methods for protein extraction from excess activated sludge.
• To analyze the performance of each method based on protein extraction rate, energy consumption, cost, and sludge dewatering.
• To evaluate the characteristics of extracted proteins for potential applications.

Main Methods:

• Acid-thermal (AT) and alkaline-thermal (AKT) for chemical extraction.
• Single enzyme (SE) and composite enzyme (CE) for enzymatic extraction.
• Ultrasonic-assisted enzyme (USE) and thermal-assisted enzyme (TE) for assisted enzymatic extraction.

Main Results:

• Chemical methods achieved protein extraction rates (R_P) >75%, surpassing enzymatic methods.
• Assisted enzymatic methods, particularly USE, significantly enhanced R_P by >39% compared to SE, with lower enzyme consumption and cost.
• USE yielded proteins rich in amino acids (animal feed), while AKT produced polypeptides (foaming agent). Sludge dewatering performance improved across all methods.

Conclusions:

• Assisted enzymatic methods, especially USE, present a promising, cost-effective approach for protein extraction from sludge.
• The choice of method influences the characteristics of the protein hydrolysates, enabling tailored applications.
• Protein extraction significantly improves sludge dewatering, aiding subsequent separation processes.