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Bioelectrochemical Detoxification of Phenolic Compounds during Enzymatic Pre-Treatment of Rice Straw
( Sanath Kondaveeti ),( Raviteja Pagolu ),( Sanjay K. S. Patel ),( Ashok Kumar ),( Aarti Bisht ),( Devashish Das ),( Vipin Chandra Kalia ),( In-won Kim ),( Jung-kul Lee ) 한국미생물 · 생명공학회 2019 Journal of microbiology and biotechnology Vol.29 No.11
The use of lignocellulosic biomass such as rice straw can help subsidize the cost of producing value-added chemicals. However, inhibitory compounds, such as phenolics, produced during the pre-treatment of biomass, hamper the saccharification process. Laccase and electrochemical stimuli are both well known to reduce phenolic compounds. Therefore, in this study, we implemented a bioelectrochemical detoxification system (BEDS), a consolidated electrochemical and enzymatic process involving laccase, to enhance the detoxification of phenolics, and thus achieve a higher saccharification efficiency. Saccharification of pretreated rice straw using BEDS at 1.5 V showed 90% phenolic reduction (Ph<sub>r</sub>), thereby resulting in a maximum saccharification yield of 85%. In addition, the specific power consumption when using BEDS (2.2 W/Kg Ph<sub>r</sub>) was noted to be 24% lower than by the electrochemical process alone (2.89 W/kg Ph<sub>r</sub>). To the best of our knowledge, this is the first study to implement BEDS for reduction of phenolic compounds in pretreated biomass.
Kondaveeti, Sanath,Patel, Sanjay K.S.,Pagolu, Raviteja,Li, Jinglin,Kalia, Vipin C.,Choi, Myung-Seok,Lee, Jung-Kul Elsevier 2019 ENERGY Vol.189 No.-
<P><B>Abstract</B></P> <P>The utilization of the greenhouse gases (methane (CH<SUB>4</SUB>) and carbon dioxide (CO<SUB>2</SUB>)) seems a suitable alternative feed to produce biofuels and value-added products to reduce their emissions. In addition, the conversion of methanol containing methanotrophic effluents to electricity using microbial fuel cells (MFCs) is limited. The sequential operation of MFC to generate electricity has proven to be beneficial because of the increase in operational performance in comparison with single stage systems. Therefore, in the present study, the methanotrophic reactor effluents were operated in air cathode MFC for electricity generation for the first time. The methanotrophic reactor with <I>Methylosinus sporium</I> produced a maximum methanol concentration of 6.45 mM using simulated biogas (4:1 (v/v) CH<SUB>4</SUB>:CO<SUB>2</SUB>) with a 50% CH<SUB>4</SUB> content. Maximum power densities of 235 and 270 mW/m<SUP>2</SUP> were noted with methanotrophic reactor effluents from pure CH<SUB>4</SUB> (MFC-1) and simulated biogas (4:1 (v/v) CH<SUB>4</SUB>:CO<SUB>2</SUB>) (MFC-2), respectively. Electrochemical impedance spectroscopy analysis revealed the presence of high charge transfer resistance as a major limitation for electricity generation. This is the first report on the sequential operation to produce methanol and electricity using simulated biogas. The system might have potential for field applications using real biogas generated through the anaerobic digestion of biowaste materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Methanotrophic reactor effluents were used to generate electricity using microbial fuel cells. </LI> <LI> Simulated biogas (4:1 (v/v) CH4:CO2) as feed showed higher methanol/electricity production than pure CH<SUB>4</SUB>. </LI> <LI> Maximum power density of 270 mW/m<SUP>2</SUP> was noted with the effluents from simulated biogas. </LI> <LI> This is the first report on the sequential operation to produce electricity from simulated biogas. </LI> </UL> </P>
Kondaveeti, Sanath,Kakarla, Ramesh,Kim, Hong Suck,Kim, Byung-goon,Min, Booki Informa UK (TaylorFrancis) 2018 Environmental Technology Vol.39 No.3
<P>This study evaluates long-term stability of low-cost separators in single-chamber bottle-type microbial fuel cells with domestic wastewater. Low-cost separators tested in this study were nonwoven fabrics (NWF) of polypropylene (PP80, PP100), textile fabrics of polyphenylene sulfide (PPS), sulfonated polyphenylene sulfide (SPPS), and cellulose esters. NWF PP80 separator generated the highest power density of 280 mW/m(2), which was higher than with ion-exchange membranes (cation exchange membrane; CEM = 271 mW/m(2), cation exchange membrane; CMI = 196 mW/m(2), Nafion = 260 mW/m(2)). MFC operations with other size-selective separators such as SPPS, PPS, and cellulose esters exhibited power densities of 261, 231, and 250 mW/m(2), respectively. During a 280-day operation, initial power density of PP80 (278 mW/m(2)) was decreased to 257 mW/m(2), but this decrease was smaller than with others (Nafion: 265-230 mW/m(2); PP100: 220-126 mW/m(2)). The anode potential of around -430 mV did not change much with all separators in the long-term operation, but the initial cathode potential gradually decreased. Fouling analysis suggested that the presence of carbonaceous substance on Nafion and PP80 after 280 days of operation and Nafion was subject to be more biofouling.</P>
Patel, Sanjay K.S.,Kondaveeti, Sanath,Otari, Sachin V.,Pagolu, Ravi T.,Jeong, Seong Hun,Kim, Sun Chang,Cho, Byung-Kwan,Kang, Yun Chan,Lee, Jung-Kul Pergamon Press 2018 Energy Vol.145 No.-
<P><B>Abstract</B></P> <P>In this study, biological methanol production under repeated batch conditions by immobilized <I>Methylocystis bryophila</I>, using simulated biogas of methane (CH<SUB>4</SUB>) and carbon dioxide (CO<SUB>2</SUB>) as a feed is demonstrated for the first time. The composition of the simulated gas mixtures significantly influenced methanol production by <I>M. bryophila,</I> and in all cases, higher concentrations were achieved than with pure CH<SUB>4</SUB> alone. Under optimum conditions, maximum methanol concentrations of 4.88 mmol L<SUP>−1</SUP>, 7.47 mmol L<SUP>−1</SUP>, and 7.02 mmol L<SUP>−1</SUP> were achieved using the gas mixtures CH<SUB>4</SUB>:CO<SUB>2</SUB> (2:1 ratio), CH<SUB>4</SUB>:hydrogen [H<SUB>2</SUB>, (4:1 ratio)], and CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB> (6:3:2 ratio), respectively, as feed, with a fixed CH<SUB>4</SUB> concentration of 30%. Methanol yield was increased to 7.85 mmol L<SUP>−1</SUP> using covalently immobilized cells and the simulated gas mixture CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB> (6:3:2 ratio). Under repeated batch conditions, immobilized cells produced a significantly higher cumulative methanol concentration (25.75 mmol L<SUP>−1</SUP>) than free cells (15.50 mmol L<SUP>−1</SUP>), using a simulated biogas mixture of CH<SUB>4</SUB>:CO<SUB>2</SUB> (2:1) and eight reuse cycles, suggesting that this mixture can potentially be utilized as a feed for the production of methanol. Furthermore, the effective utilization of low-cost feedstock, derived from natural sources, containing gas mixtures of CH<SUB>4</SUB>:CO<SUB>2</SUB>, CH<SUB>4</SUB>:H<SUB>2</SUB>, or CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB>, constitute an economical and environmentally friendly approach to the reduction of greenhouse gases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Methanol production was demonstrated by immobilized <I>Methylocystis bryophilla.</I> </LI> <LI> Simulated biogas as feed showed higher methanol production than pure CH<SUB>4</SUB>. </LI> <LI> A maximum methanol production of 7.85 mM was obtained from CH<SUB>4</SUB>:CO<SUB>2</SUB>:H<SUB>2</SUB>. </LI> <LI> Immobilized cells produced a higher cumulative methanol (25.75 mM) than free cells. </LI> </UL> </P>
Choi, Kwang-Soon,Kondaveeti, Sanath,Min, Booki Elsevier 2017 Bioresource technology Vol.245 No.1
<P><B>Abstract</B></P> <P>Microbial electrolysis cells (MECs) at various cell voltages (0.5, 0.7 1.0 and 1.5V) were operated in anaerobic fermentation. During the start-up period, the cathode potential decreased from −0.63 to −1.01V, and CH<SUB>4</SUB> generation increased from 168 to 199ml. At an applied voltage of 1.0V, the highest methane yields of 408.3ml CH<SUB>4</SUB>/g COD glucose was obtained, which was 30.3% higher than in the control tests (313.4ml CH<SUB>4</SUB>/g COD glucose). The average current of 5.1mA was generated at 1.0V at which the maximum methane yield was obtained. The other average currents were 1.42, 3.02, 0.53mA at 0.5, 0.7, and 1.5V, respectively. Cyclic voltammetry and EIS analysis revealed that enhanced reduction currents were present at all cell voltages with biocatalyzed cathode electrodes (no reduction without biofilm), and the highest value was obtained with 1V external voltage.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The difference in applied voltage have significantly altered the MEC performance. </LI> <LI> Amplification in hydrolysis process was noted in MEC with comparison to conventional AD process. </LI> <LI> At 1.0V, maximum activity of electroactive methanogenic bacteria is achieved interm of methane yield and COD removal. </LI> <LI> Acetate and Propionate were noticed as a major intermediator compounds during CH<SUB>4</SUB> generation. </LI> </UL> </P>