Enhancement of Hydrolysis and Biogas Production of Primary Sludge by Use of Mixtures of Protease and Lipase

• Published in: Biotechnology and bioprocess engineering Vol. 25; no. 1; pp. 132 - 140
• Main Authors: Tongco, Jovale Vincent, Kim, Sangmin, Oh, Baek-Rock, Heo, Sun-Yeon, Lee, Joonyeob, Hwang, Seokhwan
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Society for Biotechnology and Bioengineering 01.02.2020; Springer Nature B.V; 한국생물공학회
• Subjects: Anaerobic digestion; Anaerobic microorganisms; Anaerobic processes; Bioconversion; Biodegradation; Biogas; Bioreactors; Biotechnology; Chemistry; Chemistry and Materials Science; Degradation; Enzymes; Hydrolysis; Industrial and Production Engineering; Lipase; Methane; Microorganisms; Organic materials; Primary sludge; Protease; Proteinase; Reduction; Research Paper; Sludge; Sludge digestion; Sludge treatment; Solid suspensions; Substrates; Suspended solids; Wastewater treatment; Wastewater treatment plants; 생물공학; protease; primary sludge; enzyme cocktail; anaerobic digestion; hydrolysis; lipase
• ISSN: 1226-8372; 1976-3816
• DOI: 10.1007/s12257-019-0302-4

This study aims to improve the hydrolysis and degradation of primary sludge by using wild-type enzymes (protease and lipase) and establishing the optimal enzymatic cocktail ratio. Primary sludge from three wastewater treatment plants (WWTPs) in Korea (Ulsan, Pohang, and Busan) were subjected to enzymatic hydrolysis. Protease and lipase were isolated from enzyme-producing microorganisms cultured from secondary sludge collected at 8 different digester sites in Korea. Primary sludge degradation through enzymatic hydrolysis was monitored by measuring the reduction in the volatile suspended solids (VSS) content of the sludge and enzyme cocktail mix for 72 h at 40 o C and pH 7.0. The enzymatic cocktail of Ulsan primary sludge treated with protease to lipase at a ratio of 1:3 was found to be optimal at 33.3% VSS reduction. Biochemical methane potential (BMP) tests were employed to the optimal enzyme cocktail to measure the potential of the hydrolyzed substrate for further degradation (VSS reduction) and bioconversion to biogas using 125 mL serum bottles as anaerobic reactors for 30 days. BMP tests showed that there was an increase in biogas production by 84.1%, methane production by 89.8%, and methane yield by 9.6%. Methane production rate was also increased. The significant VSS concentration reduction and higher biogas and methane yield of the enzyme-treated primary sludge correlate to the fact that the complex polymeric organic materials were degraded leading to efficient utilization by the microorganisms in the anaerobic digestion process.