title: Anaerobic digestion of cattle offal: protein and lipid-rich substrate degradation and population dynamics of acidogens and methanogens.
abstract: Anaerobic digestion of cattle offal was investigated in batch reactors at 35 °C to determine the feasibility of using cattle offal as a feedstock. The organic content [i.e., volatile solids (VS)] of the cattle offal was mainly composed of protein (33.9%) and lipids (46.1%). Hydrolysis along with acidogenesis was monitored to investigate the substrate degradation and generation of intermediate products (e.g., volatile fatty acids, ammonia). Acetate (2.03 g/L), propionate (0.60 g/L), n-butyrate (0.39 g/L), and iso-valerate (0.37 g/L) were major acidogenesis products (91% of total volatile fatty acid concentration). Overall protein and lipid degradation were 82.9 and 81.8%, respectively. Protein degraded first, and four times faster (0.28 day(-1)) than lipid (0.07 day(-1)). Methane yields were 0.52 L CH4/g VSadded and 0.65 L CH4/g VSremoved, indicating that anaerobic digestion of the offal was feasible. A quantitative QPCR assay was conducted to understand the microbial dynamics. The variation patt erns in the gene concentrations successfully indicated the population dynamics of proteolytic and lipolytic acidogens. A fourth-order Runge-Kutta approximation was used to determine the kinetics of the acidogens. The molecular biotechnology approach was appropriate for the evaluation of the acidogenic biokinetics. The maximum growth rate, μ m, halfsaturation coefficients, K s, microbial yield coefficient, Y, cell mass decay rate coefficient, k d, of the proteolytic acidogens were 9.9 day(-1), 37.8 g protein/L, 1.1 × 10(10) copies/g protein, and 3.8 × 10(-1), respectively. Those for the lipolytic acidogens were 1.2 × 10(-1) day(-1), 8.3 g lipid/L, 1.5 × 10(9) copies/g lipid, and 9.9 × 10(-3) day(-1), respectively.
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 790-784, Republic of Korea.
authors.forename: Joonyeob
authors.initials: J
authors.lastname: Lee
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 790-784, Republic of Korea.
authors.forename: Taewoan
authors.initials: T
authors.lastname: Koo
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 790-784, Republic of Korea.
authors.forename: Gyuseong
authors.initials: G
authors.lastname: Han
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 790-784, Republic of Korea.
authors.forename: Seung Gu
authors.initials: SG
authors.lastname: Shin
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 790-784, Republic of Korea. shwang@postech.ac.kr.
authors.forename: Seokhwan
authors.initials: S
authors.lastname: Hwang
mesh_terms: D000003:Abattoirs; D000693:Anaerobiosis; D000818:Animals; D001105:Archaea / Q000235:genetics / Q000378:metabolism*; D001421:Bacteria, Anaerobic / Q000235:genetics / Q000378:metabolism*; D019149:Bioreactors; D002417:Cattle; D050356:Lipid Metabolism; D011506:Proteins / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D011506:Proteins; D012336:RNA, Ribosomal, 16S
keywords: Anaerobic digestion; Cattle offal; Protein and lipid degradation; QPCR; Slaughterhouse by-products