Effect of chemical input during wet air oxidation pretreatment of rice straw in reducing biomass recalcitrance and enhancing cellulose accessibility

Amruta Morone,Tapan Chakrabarti,R. A. Pandey 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.12

The present study was aimed at evaluating the effect of variable sodium carbonate (Na2CO3) loading during wet air oxidation (WAO) pretreatment of rice straw in reducing biomass recalcitrance. The research study was intended to increase the cellulose recovery, hemicellulose solubilization, lignin removal in the solid fraction and limiting the generation of inhibitors in the liquid fraction while reducing the chemical input. The operating condition of 169 oC, 4 bar, 18 min and 6.5 g/L Na2CO3 loading resulted in maximum cellulose recovery of 82.07% and hemicellulose solubilization and lignin removal of 85.43% and 65.42%, respectively, with a total phenolic content of 0.36 g/L in the liquid fraction. The crystallinity index increased from 47.69 to 51.25 along with enzymatic digestibility with an increase in Na2CO3 loading from 0 to 6.5 g/L as a result of removal of barriers for saccharification via effective cleavage of ether and ester bonds cross-linking the carbohydrates and lignin as indicated by FT-IR spectroscopy. A further increase in the Na2CO3 loading to 9.5 g/L did not significantly increase the sugar release. Thus, it was concluded that 6.5 g/L Na2CO3 during WAO is sufficient to increase the delignification and deacetylation, leading to significant changes in apparent cellulose crystallinity inter alia improvement in cellulose accessibility and digestibility of rice straw.

Carbamazepine and oxcarbazepine removal in pharmaceutical wastewater treatment plant using a mass balance approach: A case study

Kshitiz Dwivedi,Amruta Morone,Vishwas Pratape,Tapan Chakrabarti,Ram Avtar Pandey 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.10

The manufacturing of the antiepileptics, carbamazepine (CBZ) and oxcarbazepine (oxCBZ), results in generation of wastewater containing these micropollutants which exhibit toxicity even at trace levels. Therefore, we focused on monitoring their fate and removal in various units of a full-scale wastewater treatment plant (WWTP) using mass balance approach. An apparent CBZ removal of 50±3% was observed by conventional activated sludge process in the biological treatment unit, whereas oxCBZ still persisted after the biological treatment and showed negative mass balance. However, reverse osmosis resulted in 91% oxCBZ removal, whereas CBZ still continued to persist as a result of lower solubility of CBZ as compared to oxCBZ. Only 3% CBZ exhibited sorption onto the suspended solids and sludge, which was negligible for oxCBZ, thus demonstrating their tendency to remain in aqueous phase. Additionally, we attempted to understand the fundamental mechanism behind the removal of these pharmaceuticals and it was apparently the collective effect of sorption, mineralization, biotransformation, biodegradation, phototransformation/ photodegradation, etc. Thus, the integrative data presented in the present study on productivity of these pharmaceuticals, their mass loading in influent and effluents allied with their removal efficiency will be significantly constructive in benchmarking the operational effectiveness through operational optimization and design improvement of the current conventional treatment plant.

Purification and Characterization of a Novel Plant-type Carbonic Anhydrase from Bacillus subtilis

Rishiram Ramanan,Krishnamurthi Kannan,Nadimuthu Vinayagamoorthy,Saravana Devi Sivanesan,Kunga Mohan Ramkumar,Tapan Chakrabarti 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.1

Carbonic anhydrase enzyme, one of the fastest known enzymes, remains largely unexplored in prokaryotes when compared to its mammalian counterparts despite its ubiquity. In this study, the enzyme has been purified from Bacillus subtilis SA3 using sequential Sephadex G-75 chromatography, DEAE cellulose chromatography, and sepharose-4B-L-tyrosine-sulphanilamide affinity chromatography and characterized to provide additional insights into its properties. The apparent molecular mass of carbonic anhydrase obtained by SDS-PAGE was found to be approximately 37 kDa. Isoelectric focusing of the purified enzyme revealed an isoelectric point (pI) of around 6.1 when compared with marker. The presence of metal ions such as Zn2+, Co2+, Cu2+, Fe3+, Mg2+, and anion SO4- increased enzyme activity while strong inhibition was observed in the presence of Hg2+, Cl-, HCO3-, and metal chelator EDTA. The optimum pH and temperature for the enzyme were found to be 8.3 and 37℃, respectively. Enzyme kinetics with p-nitrophenyl acetate as substrate at pH 8.3 and 37℃ determined the Vmax and Km values of the enzyme to be 714.28 μmol/mg protein/min and 9.09 mM, respectively. The Ki value for acetazolamide was 0.22 mM, compared to 0.099 mM for sulphanilamide. The results from N-terminal amino acid sequencing imply the purified protein is a putative beta-carbonic anhydrase with close similarities to CAs from plants, microorganisms.

Influence of CO₂ concentration on carbon concentrating mechanisms in cyanobacteria and green algae: a proteomic approach

Ramanan, Rishiram,Vinayagamoorthy, Nadimuthu,Sivanesan, Saravana Devi,Kannan, Krishnamurthi,Chakrabarti, Tapan The Korean Society of Phycology 2012 ALGAE Vol.27 No.4

Carbon concentrating mechanisms play a vital role in photosynthesis in microalgae and cyanobacteria especially in the proper functioning of Rubisco and assimilation of carbon via the Calvin cycle. This study evaluates the role of carbon dioxide on carbon concentrating mechanism (CCM) in a cynaobacteria, Spirulina platensis and a microalga, Chlorella sp. 786. The study organisms were grown in both atmospheric (control sample, 0.035%) and high (exposed sample, 10%) $CO_2$ concentrations. Second dimension (2D) electrophoresis revealed a huge difference in the protein profiles of both organisms suggesting the induction of CCM related proteins in the sample maintained at atmospheric $CO_2$ concentration and the repression of CCM related proteins in the sample maintained at 10% $CO_2$. Liquid chromatography-mass spectroscopy analysis revealed the presence of two important $C_i$ transporter proteins in the control sample of S. platensis, namely ferredoxin-$NADP^+$ reductase and ATP binding cassette (ABC) transport system protein. These proteins were only expressed in the control sample and were downregulated or not expressed at all in the exposed sample. Consequently, this study conclusively proves that CCMs are only inducted at low $CO_2$ concentrations and are not functional at high $CO_2$ concentration.

Influence of CO2 concentration on carbon concentrating mechanisms in cyanobacteria and green algae: a proteomic approach

Rishiram Ramanan,Nadimuthu Vinayagamoorthy,Saravana Devi Sivanesan,Krishnamurthi Kannan,Tapan Chakrabarti 한국조류학회I 2012 ALGAE Vol.27 No.4

Carbon concentrating mechanisms play a vital role in photosynthesis in microalgae and cyanobacteria especially in the proper functioning of Rubisco and assimilation of carbon via the Calvin cycle. This study evaluates the role of carbon dioxide on carbon concentrating mechanism (CCM) in a cynaobacteria, Spirulina platensis and a microalga, Chlorella sp. 786. The study organisms were grown in both atmospheric (control sample, 0.035%) and high (exposed sample, 10%)CO2 concentrations. Second dimension (2D) electrophoresis revealed a huge difference in the protein profiles of both organisms suggesting the induction of CCM related proteins in the sample maintained at atmospheric CO2 concentration and the repression of CCM related proteins in the sample maintained at 10% CO2. Liquid chromatography-mass spectroscopy analysis revealed the presence of two important Ci transporter proteins in the control sample of S. platensis,namely ferredoxin-NADP+ reductase and ATP binding cassette (ABC) transport system protein. These proteins were only expressed in the control sample and were downregulated or not expressed at all in the exposed sample. Consequently,this study conclusively proves that CCMs are only inducted at low CO2 concentrations and are not functional at high CO2concentration.