다양한 기질을 처리하는 서로 다른 혐기소화조의 프로피온산 분해 미생물 군집

Abstract

Producing a large amount of organic wastewater such as Food Waste Recycling Wastewater (FWRWW), swine wastewater and domestic sewage has been serious problem in South Korea, and anaerobic digestion technologies are also effective means for the treatment of different organic pollutants and the production of energy. Operating anaerobic digestors, the accumulation of various short chain volatile fatty acids (VFAs) has been the main issue which had caused process imbalances. In particular, propionate is an important intermediate in anaerobic digestions which may account for 35% of the total methanogenesis in digestors and its high concentration was reported to be inhibitory to methanogens. We collected biomass samples from 10 different field-scale anaerobic reactors and conducted repeated batch culture to obtain the most rapid propionate-utilizing biomass (RPB). The Gompertz model was used to draw the description of methane production and especially the maximum methane production rate (μm) was used as an indicator of RPB. Seven biomass samples enabled microorganisms in the anaerobic system to produce methane gas along with the degradation of propionate

while other 3 samples did not work during 108 days at given experimental periods. Only 4 biomass samples, which came from domestic sewage treating digestors, could reach 7th batch culture, whereas other 3 biomass samples could not. D3 biomass showed the highest μm that was 109.1±4.2 (mL CH4 /g propionate-day) and D2 was followed that μm was 74.5±8.6 (mL CH4 /g propionate-day) in the 1st batch culture. To investigate microbial communities of RPB, denaturing gel gradient electrophoresis (DGGE) using bacterial and archaeal 16S rRNA genes were carried out. D3 and D2 biomass shared common microorganisms that were related to Smithella propionica and Methanosaeta concilii in the 1st batch culture

however, in case of others, S. propionica-like organisms were not detected. Two biomass samples, D1 and D2, (their μm values were 130.2±8.2 and 133.8±8.2 mL CH4 /g propionate-day in the 7th batch culture, respectively.) were procured as RPB from 10 different field-scale digestors through repeated-batch culture. Two common predominant microorganisms were detected. In other words, S. propionica-related organism was turned out to be the dominant propionate oxidizing bacteria (POB) and M. concilii-associated organisms were the dominant methanogen in RPB biomass. Judging from this, a “six-carbon intermediate” pathway, which can be mediated by S. propionica, was speculated to take an advantage of rapid propionate degradation rather than the conventional step of propionate degradation, methyl-malonyl-CoA pathway. Also, procured RPB samples had the possibility to be used as bioaugmentation if there would be propionate accumulation problem in anaerobic digestors