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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>
Immobilization of Xylanase Using a Protein-Inorganic Hybrid System
( Ashok Kumar ),( Sanjay K. S. Patel ),( Bharat Mardan ),( Raviteja Pagolu ),( Rowina Lestari ),( Seong-hoon Jeong ),( Taedoo Kim ),( Jung Rim Haw ),( Sang-yong Kim ),( In-won Kim ),( Jung-kul Lee ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.4
In this study, the immobilization of xylanase using a protein-inorganic hybrid nanoflower system was assessed to improve the enzyme properties. The synthesis of hybrid xylanase nanoflowers was very effective at 4°C for 72 h, using 0.25 mg/ml protein, and efficient immobilization of xylanase was observed, with a maximum encapsulation yield and relative activity of 78.5% and 148%, respectively. Immobilized xylanase showed high residual activity at broad pH and temperature ranges. Using birchwood xylan as a substrate, the V<sub>max</sub> and K<sub>m</sub> values of xylanase nanoflowers were 1.60 mg/ml and 455 μmol/min/mg protein, compared with 1.42 mg/ml and 300 μmol/min/mg protein, respectively, for the free enzyme. After 5 and 10 cycles of reuse, the xylanase nanoflowers retained 87.5% and 75.8% residual activity, respectively. These results demonstrate that xylanase immobilization using a proteininorganic hybrid nanoflower system is an effective approach for its potential biotechnological applications.