Recent advances in commercial biorefineries for lignocellulosic ethanol production: Current status, challenges and future perspectives.

Recent advances in commercial biorefineries for lignocellulosic ethanol production: Current status, challenges and future perspectives

• Key aspects of cyclic adsorption processes (PSA, TSA, VSA etc.) are discussed. • Main concepts of derived adsorbents from biomass/biochar are presented. • A review on developed cyclic adsorption processes using biomass/biochar is illustrated. • Biomass/biochar are introduced as future studies for cyclic adsorption processes. The persistent enhancement of greenhouse gases in the atmosphere originated from anthropogenic activities, especially CO 2 , resulted in several serious global challenges. In this way, employing biomass, biochar, etc., as a low-cost precursor for CO 2 adsorbent is promising not only in the view of hydrophobic character and abundant resources, but also is an illustrious strategy for solid wastes management as a consequence of the exponential population expansion. Herein, key concepts on adsorption technology, waste management, and different activation techniques on raw carbons materials have firstly been discussed. Afterwards, almost all accomplished studies on cyclic adsorption processes e.g. PSA, TSA, VSA, etc., which employed biomass/biochar as a source of adsorbents have been extensively reviewed, that gives a precise knowledge for large scale application of these materials. Furthermore, in the last part of this work, biomass/biochar adsorbent based samples, which have already been studied for CO 2 capture, but till now, they have not been evaluated at the bench/pilot scale by cyclic adsorption process, are introduced for future directions. Also for the reader’s of this work, key concepts of each section have been summarized in the form of simple figures and tables that will help to identify clearly the prominent accomplished works till now. 

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Biomass/Biochar carbon materials for CO2 capture and sequestration by cyclic adsorption processes: A review and prospects for future directions

Lignin valorisation via enzymes: A sustainable approach

Dye wastewater discharged after improper treatment is very harmful for environment and living creatures. As per mandate, the dye wastewater should be treated well in order to prevent any negative effects after discharge. Although there are various methods which are in use, however most of these methods have some or the other associated disadvantages i.e., high cost, generation of secondary pollutants, low efficiency, complexity etc. The objective of this study is to identify the dye degradation (orange and blue dye-individually/mixture) potential of chemically synthesized silver nanoparticles (CH-AgNPs) along with NaBH4. Literature studies highlighted the efficacy of AgNPs for individual dye degradation, however it is very important to study the degradation potential of nanoparticles in presence of dye mixture (to mimic the natural wastewater condition). In the present study, the rapid synthesis of silver nanoparticles (CH-AgNPs) was obtained by using trisodium citrate solution. The developed CH-AgNPs were examined for UV–vis Spectrophotometry (maxima-422 nm), Zeta Potential (−6.70 ​mV), and Transmission Electron Microscopy (spherical shape with size range of 8–40 ​nm), highlighting the nano-size and stability of synthesized CH-AgNPs. For catalytic activity, CH-AgNPs and NaBH4 were tested for dye degradation potential for Orange and Blue dyes individually and in mixture (orange ​+ ​blue dye). It was observed that with increase in dye concentration from 50 ​ppm to 200 ​ppm, NaBH4 showed 28% and 25% removal for blue and orange dyes, respectively. However, when CH-AgNPs ​+ ​NaBH4 was used, up to 100% degradation was obtained from blue dye, however the degradation of orange dye has shown 97.4% degradation. Further, as the wastewater contains multiple dyes, therefore in dye mixture studies (orange ​+ ​blue dye- 50 ​ppm), 100% degradation was achieved with NaBH4+CH-AgNPs in just 5 ​min, highlighting the efficient catalytic ability of NaBH4+AgNPs. The results clearly highlighted the potential of CH-AgNPs in enhancing the dye degradation of orange and blue dyes-individually and in mixture, therefore the present study is relevant for further research to identify the best dye degradation agents, especially in presence of dyes mixture.

Silver nanoparticles for enhanced dye degradation

Cellulosic and hemicellulosic fractions of sugarcane bagasse: Potential, challenges and future perspective

Thermophilic mould Sporotrichum thermophile BJTLRMDU7 played the role in greener synthesis of the silver nanoparticles (AgNPs) extracellularly using silver nitrate. The change in colour from transparent to dark brown primarily indicated the formation of AgNPs due to reduction of Ag (I) ions to Ag by the fungal culture extract. Nanoparticles synthetic process was optimized using “one variable at a time” approach. Sucrose containing medium having pH 8.0 supported the synthesis of AgNPs by the mould at 45 ​°C. Furthermore, presence of light significantly accelerated the formation of silver nanoparticles. AgNPs were characterized by various techniques like UV–vis & FT-IR spectroscopy, dynamic light scattering (DLS) and X-ray diffraction (XRD). Appearance of a band at 426 ​nm in UV–vis spectrum revealed the reduction of Ag(I) ions to Ag (0) by mould’s culture filtrate. DLS data showed that AgNPs bear an average size of 70 ​nm, while XRD data revealed particle size of 40 ​nm. The application of AgNPs with their functional group transformation has successfully reduced p-nitrophenol into p-aminophenol in an eco-friendly manner in the presence of light and NaBH4. Further, the synthesized AgNPs showed anti-bacterial potential against Gram positive and Gram negative bacteria.

Sporotrichum thermophile culture extract-mediated greener synthesis of silver nanoparticles: Eco-friendly functional group transformation and anti-bacterial study

Experimental and Computational Validation of Structural Features and BSA Binding Tendency of 5-Hydroxy-5-trifluoromethyl-3-arylpyrazolines**

An extremely simple, expeditious and greener synthetic method for a variety of chalcone derivatives (3) under mild and solvent free reaction conditions has been developed. The present protocol discloses the use of p-toluenesulfonic acid (p-TSA) as a solid phase organocatalyst which accelerates the Claisen–Schmidt condensation reaction dramatically under mild conditions. Various aryl aldehydes (1) were treated with differently substituted aryl ketones (2) in the presence of p-TSA at 50–60 ​°C to yield the desired products in a very short period of reaction time. Mild reaction conditions, clean reaction media, expulsion of hazardous solvents, simple work-up, exclusive formation of products in high yields without side products, and easy purification are advantages of the present methodology.

Simple and solvent free practical procedure for chalcones: An expeditious, mild and greener approach

Open rice straw burning has created hazardous effects on the environment and human health. Biological pretreatment of rice straw has been proven as an environmental-benign and economical feasible process for the production of biofuels and value-added products under milder and greener conditions by avoiding harmful chemicals and toxic reagents. A consolidated bioprocess for the production of cellulolytic enzymes and biological pretreatment was developed to achieve a cost-effective saccharification of rice straw. Biodegradation of biomass was slightly enhanced with increase in cultivation time of microbial pretreatment. Furthermore, the modification in biomass due to biological pretreatment weakened the interaction between hemicellulose and lignin that resulted in significant reduction in lignin using Bacillus subtilis subsp. subtilis JJBS300, Myceliophthora thermophila BJTLRMDU3, and Aspergillus oryzae SBS50 for biological pretreatment of rice straw. Bacterial culture produced maximum FPase, CMCase, and β-glucosidase of 28, 17, and 20.36 U/g DMR after 2 days during pretreatment process, whereas M. thermophila produced maximum FPase (85.10 U/g DMR), CMCase (96.89 U/g DMR), and β-glucosidase (91.92 U/g DMR) after 9 days. The mold A.oryzae SBS50 also produced maximum FPase (57.41 U/g DMR), CMCase (55.36 U/g DMR), and β-glucosidase (48.04 U/g DMR) after 9 days of pretreatment. Maximum amount of reducing sugars of 52.41, 86.74, and 49.59 mg/g substrate were liberated from 6-, 5-, and 3-day-old biological pretreated rice straw by B. subtilis, M. thermophila, and A. oryzae, respectively, after enzymatic hydrolysis for 6 h at 60 oC and pH 5.0. Laccase-pretreated rice straw followed by enzymastic saccharification resulted in liberation of 162.82 mg/g reducing sugars at pH 5.0 and 60 °C after 6h using 20 U/g cellulase. Simultaneous laccase pretreatment and saccharification (SLPS) process further enhanced the liberated reducing sugars, i.e., 179.47 mg/g substrate. FTIR, XRD, and SEM analyses showed marked morphological changes as a result of delignification after biological pretreatment of rice straw. Biological pretreatment being an environmental-benign process causing no harm to the environment in comparison to physical and chemical pretreatments of lignocellulosic biomass could be a better pretreatment strategy for bioremediation of lignocellulosic substrates.

Vinod Kumar

Papers

Cellulosic and hemicellulosic fractions of sugarcane bagasse: Potential, challenges and future perspective

Sporotrichum thermophile culture extract-mediated greener synthesis of silver nanoparticles: Eco-friendly functional group transformation and anti-bacterial study

Experimental and Computational Validation of Structural Features and BSA Binding Tendency of 5-Hydroxy-5-trifluoromethyl-3-arylpyrazolines**

Simple and solvent free practical procedure for chalcones: An expeditious, mild and greener approach

A greener, mild, and efficient bioprocess for the pretreatment and saccharification of rice straw