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Arma Yulisa,Joonyeob Lee,Sang Hyeok Park,Seokhwan Hwang 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.6
Electromethanogenesis (EM) is a system that facilitates direct interspecies electron transfer (DIET) in anaerobic digestion (AD) by providing an external power supply to favor desired reactions. Substrates of AD commonly contain ammonia (NH₃) as biodegradation product of nitrogen-rich compounds that can deteriorate the stability of AD process. Optimized cathode potential (VCAT) and magnetite (Mag) concentration ([Mag]) are expected to improve AD efficiency in the presence of NH₃. Response surface analysis with central composite face-centered design was used in this study to investigate the effect of VCAT and [Mag] under different total ammonia nitrogen concentration ([TAN]). Highest cumulative methane production was achieved at VCAT = -737.4 mV, [Mag] = 18.2 mM, and [TAN] = 1.5 g/L; highest acetate degradation rate was achieved at VCAT = 757.6 mV, [Mag] = 21.4 mM, and [TAN] = 1.5 g/L. The study demonstrated that VCAT promotes either microbial growth or electrochemical NH₃ removal. A Shift from acetoclastic to hydrogenotrophic pathway was also observed by the increase of hydrogenotrophic methanogen populations at the end of experiment. This study is beneficial for process control of AD under different NH₃ conditions.
차야니,YULISA ARMA,박상혁,JANNAT MD ABU HANIFA,황석환 한국생물공학회 2022 Biotechnology and Bioprocess Engineering Vol.27 No.4
Olive flounder (OF) and Starry flounder (SF) are the commonly cultured fish species in the South Korea East Sea. Evaluation of whether those dead fish wastes are suitable for anaerobic digestion is required. The aim of this study was to characterize the physicochemical properties of each fraction which was flesh, bone, head, skin, viscera, and whole fish OF and SF and evaluate their biochemical methane potential (BMP). The results showed that both dead fish species’ wastes mainly contained proteins (48- 75% of volatile solids [VS]) and lipids (19-40% of VS), whereas carbohydrates were little found (0.7-5% of VS). The BMP of each fraction was investigated in a mesophilic condition and the substrate-to-microbe ratio was 0.5 g CODsubstrate/g VSSinoculum. The results showed that the bone fractions in both OF and SF showed the highest methane yield with 0.37 and 0.38 L CH4/g CODadded, respectively whereas the viscera fractions of both fish species showed the lowest methane yield with 0.20 L CH4/g CODadded. The modified Gompertz model showed that the longest lag phase was observed in the bone fractions of OF and SF with 1.59 d and 2.62 d and the shortest lag phase was in the viscera fraction of OF and SF with 0.37 d and 0.58 d, respectively. The energy recovery of every fraction of both species ranged 43-69%. Principal component analysis indicated that the viscera fraction of OF and SF had different characteristics from the other fractions. This study suggests that dead fish wastes can be considered for biogas production.
Lee, Joonyeob,Koo, Taewoan,Yulisa, Arma,Hwang, Seokhwan Academic Press 2019 Journal of Environmental Management Vol. No.
<P><B>Abstract</B></P> <P>Anaerobic batch tests with a 2<SUP>2</SUP> full-factorial design of ammonia (1.5, 6.5 g N/L) and magnetite concentrations (0, 20 mmol/L) were conducted separately for methanogenic degradation of acetate, propionate, and butyrate (volatile fatty acids (VFAs)) to 1) quantify the effect of magnetite as an enhancer in methanogenic degradation of each of the VFAs in conditions without ammonia stress (1.5 g N/L) and with ammonia stress (6.5 g N/L), and 2) identify methanogenic consortia that are related to such enhancement. Among the three VFAs, methanogenic degradation of propionate was the least feasible (57% lower specific methanogenic activity <I>R</I> <SUB> <I>CH4</I> </SUB> and three times longer lag time <I>λ</I> than acetate degradation). At low ammonia concentration, only propionate showed improvement in <I>R</I> <SUB> <I>CH4</I> </SUB> (46%) with supplementation of magnetite. In the ammonia-stressed condition without magnetite, <I>R</I> <SUB> <I>CH4</I> </SUB> decreased by 38–58% and <I>λ</I> increased 2.2–8.8 times for all VFAs; magnetite supplementation significantly alleviated these effects. These results demonstrate that magnetite supplementation effectively increases methanogenic degradation of the VFAs even under ammonia-stressed conditions. 16S metagenomic sequencing revealed that distinctive methanogenic consortia were active in the different combinations of substrate, ammonia and magnetite. <I>Alkaliphilus</I>, <I>Hyphomonadaceae SWB02</I> and <I>Clostridia DTU014</I>, <I>Clostridia D8A-2</I>, <I>Christensenellaceae R-7 group</I> and <I>Rikenellaceae DMER64</I> were identified as potential syntrophic bacteria that can establish magnetite-mediated direct electron transfer with methanogens (<I>Methanosaeta concilii</I>, <I>Methanosaeta harundinacea</I>, <I>Methanolinea tarda</I>, <I>Methanoculleus bourgensis</I> and <I>Methanosarcina</I> spp.) during methanogenic degradation of VFAs. The results may be useful as a reference to develop effective strategies using magnetite supplementation to remediate anaerobic digestion processes that have been afflicted by VFA accumulation and ammonia inhibition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Magnetite effect on AD of VFAs under NH<SUB>3</SUB>-stressed condition was tested. </LI> <LI> Methanogenic degradation of propionate was improved by magnetite addition. </LI> <LI> Magnetite alleviated NH<SUB>3</SUB> inhibition of methanogenic degradation of VFAs. </LI> <LI> Distinctive syntrophic consortia were responsible for such enhancement effect. </LI> </UL> </P>