Alankar Vaidya - Academia.edu (original) (raw)

Papers by Alankar Vaidya

Biomass Conversion and Biorefinery, 2022

A clean and efficient fractionation of biomass into cellulose, hemicellulose and lignin streams i... more A clean and efficient fractionation of biomass into cellulose, hemicellulose and lignin streams is a key step in biofuel and biorefinery industries. Lignin-free cellulose and hemicellulose streams can be enzymatically hydrolysed to sugars for fermentation to different biofuels, high value biochemicals and biopolymers. Towards this objective, organosolv pretreatment is the promising strategy to separate lignin from carbohydrates. Scientific information on the organosolv pretreatment using lignocellulosic biomass in general and various organic wastes is available with a focus on lignin separation and its use. Amongst different lignocellulosic biomass, softwood is a challenging feedstock due to recalcitrance towards enzymatic hydrolysis of cellulose. The aim of this review is to describe technical and research efforts on various organosolv processes developed specifically for softwood as a feedstock and how it influences enzymatic hydrolysis of cellulose. Process severity factor, selec...

Handbook of Bioenergy Crop Plants, 2012

Polymer, 2000

A series of copolymers of N-isopropylacrylamide (NIPA) and acryloyl amino acids were synthesized ... more A series of copolymers of N-isopropylacrylamide (NIPA) and acryloyl amino acids were synthesized and conjugated with p-aminobenzamidine (PABA). The values of lower critical solution temperatures (LCSTs) of these polymers estimated by 1 H NMR were in agreement with those estimated by the turbidometric methods. The apparent shifts in the peak positions for the polymer with increasing temperature reported in the past are shown to be artifacts resulting from the deuterium lock experiment. The 1 H± 1 H NOESY experiments were carried out to distinguish the interactions between the protons in: (a) 6-amino caproic acid (6ACA) and NIPA and (b) PABA and NIPA. These explain the variation in the LCST of the polymers based on the contributions of the two monomers to the magnitude of the polymer±polymer interactions. The ®ndings are further supported by proton spin±lattice relaxation time measurements.

Journal of Crystal Growth, 2005

... [4] RL Ryall, World J. Urol. 15 (1997), pp. 155164. Full Text via CrossRef | View Record in ... more ... [4] RL Ryall, World J. Urol. 15 (1997), pp. 155164. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (36). [5] M. Deepa, K. Rajendra Babu and VK Vaidyan, J. Mater. Sci. Lett. 132 (1993), p. 617. [6] N. Srinivasan and S. Natarajan, Indian J. Phys. ...

ChemBioChem, 2003

In the past ™molecular imprinting∫ was mainly confined to the separation of organic molecules and... more In the past ™molecular imprinting∫ was mainly confined to the separation of organic molecules and to nonenzymatic catalysis. [1±3] With advancements in this technology, its potential and utility in the field of biotechnology was also realized. [4] In order to improve its applicability, new variations in the conventional imprinting technique have emerged, such as ™bioimprinting∫, [5, 6] metal chelation imprinting, [7] affinity imprinting, [8, 9] and a combination of immobilization and ™bioimprinting∫. [10, 11] The memory effect of enzymes caused by bioimprinting without a further immobilization step was found to depend on the water content of the medium and was completely lost when the reaction was carried out in the presence of a certain amount of water. [5, 12, 13] This was exemplified by the fact that, in aqueous medium, renaturation of a bioimprinted protein to its original native conformation resulted in the loss of imprinted memory. [5, 13] However, water is an indispensable milieu for most enzymatic reactions. Therefore, our research is focused on how to maintain the ™bioimprinted memory∫ of an enzyme not only in organic solvents but also in aqueous solution systems. Here we demonstrate that the combinatorial crosslinked imprinting approach (we termed it CLIP) overcomes this problem. The CLIP methodology is shown schematically in Scheme 1. Keyes et al. employed a different kind of methodology to alter the catalytic properties of enzymes. [14] In their strategy, the enzyme complexed with ligands was crosslinked by using glutaraldehyde. This whole process was carried out in aqueous buffer, probably because the present imprinting concept in organic solvents was not known to that time. In our initial attempts [10] monomeric, low-molecular-weight (26 ± 28 kDa), nonglycosylated and cofactor-independent proteolytic enzymes, such as chymotrypsin and subtilisin, were selected to demonstrate the feasibility of the CLIP approach to rationally modify their catalytic properties. These proteases, when ™bioimprinted∫ with N-acetyl-D-tryptophan, can accept both D-and L-configured substrates, whereas the native enzyme only recognizes the L-form for synthesis of its ethyl ester in dry

Biochemical and Biophysical Research Communications, 1999

Applied Biochemistry and Biotechnology, 2007

The objective of this study was to covalently immobilize Candida antarctica type B lipase (CALB) ... more The objective of this study was to covalently immobilize Candida antarctica type B lipase (CALB) onto silanized green coconut fibers. Variables known to control the number of bonds between enzyme and support were evaluated including contact time, pH, and final reduction with sodium borohydride. Optimal conditions for lipase immobilization were found to be 2 h incubation at both pH 7.0 and 10.0. Thermal stability studies at 60 degrees C showed that the immobilized lipase prepared at pH 10.0 (CALB-10) was 363-fold more stable than the soluble enzyme and 5.4-fold more stable than the biocatalyst prepared at pH 7.0 (CALB-7). CALB-7 was found to have higher specific activity and better stability when stored at 5 degrees C. When sodium borohydride was used as reducing agent on CALB-10 there were no improvement in storage stability and at 60 degrees C stability was reduced for both CALB-7 and CALB-10.

Journal of Applied Polymer Science, 2001

A molecularly imprinted polymeric receptor for trypsin was synthesized by employing a novel techn... more A molecularly imprinted polymeric receptor for trypsin was synthesized by employing a novel technique that is a combination of affinity separation and molecular imprinting. An enzyme-inhibitor complex of trypsin and N-acryloyl para-aminobenzamidine was polymerized with acrylamide and N,N'-methylene bis-acrylamide. Template trypsin was extracted out to obtain an affinity-imprinted polymer. Control experiments were performed to demonstrate the synergistic affinity-imprinting effect. The percentage of crosslinker used was the crucial factor in determining the imprinting efficacy of the polymers. Imprinted polymer containing 50% crosslinker exhibited a linear Scatchard plot. Unlike non-imprinted gel, the receptor exhibited almost exclusive recognition of trypsin in an individual batch experiment as well as from a mixture of trypsin and chymotrypsin.

World journal of microbiology & biotechnology, 2021

Biogas and biohydrogen are compatible gaseous biofuels that can be blended with natural gas for r... more Biogas and biohydrogen are compatible gaseous biofuels that can be blended with natural gas for reticulated fuel supply to reduce greenhouse gas emissions. Sustainably grown woody biomass is emerging as a potential feedstock in the production of biofuels. Woody biomass is widely available, uses non-arable land for plantation, does not require synthetic fertilisers to grow and acts as a carbon sink. The cellulose and hemicellulose fractions of wood are renewable sources of sugars that can be used for fermentative production of gaseous biofuels. However, widespread use of wood as a gaseous biofuel feedstock is constrained due to the recalcitrant nature of wood to enzymatic hydrolysis. Pretreatment makes cellulose and hemicellulose accessible to microbial enzymes to produce fermentable sugars. Here we review wood composition, its structure and different pretreatment techniques in the context of their effects on deconstruction of wood to improve hydrolysis and fermentative gaseous fuel ...

Industrial Crops and Products

Materials Today Communications

Biotechnology for biofuels, 2017

Conversion of softwoods into sustainable fuels and chemicals is important for parts of the world ... more Conversion of softwoods into sustainable fuels and chemicals is important for parts of the world where softwoods are the dominant forest species. While they have high theoretical sugar yields, softwoods are amongst the most recalcitrant feedstocks for enzymatic processes, typically requiring both more severe pretreatment conditions and higher enzyme doses than needed for other lignocellulosic feedstocks. Although a number of processes have been proposed for converting softwoods into sugars suitable for fuel and chemical production, there is still a need for a high-yielding, industrially scalable and cost-effective conversion route. We summarise work leading to the development of an efficient process for the enzymatic conversion of radiata pine (Pinus radiata) into wood sugars. The process involves initial pressurised steaming of wood chips under relatively mild conditions (173 °C for 3-72 min) without added acid catalyst. The steamed chips then pass through a compression screw to sq...

Scientific Reports, 2017

Mapping the location of bound cellulase enzymes provides information on the micro-scale distribut... more Mapping the location of bound cellulase enzymes provides information on the micro-scale distribution of amenable and recalcitrant sites in pretreated woody biomass for biofuel applications. The interaction of a fluorescently labelled cellulase enzyme cocktail with steam-exploded pine (SEW) was quantified using confocal microscopy. The spatial distribution of Dylight labelled cellulase was quantified relative to lignin (autofluorescence) and cellulose (Congo red staining) by measuring their colocalisation using Pearson correlations. Correlations were greater in cellulose-rich secondary cell walls compared to ligninrich middle lamella but with significant variations among individual biomass particles. The distribution of cellulose in the pretreated biomass accounted for 30% of the variation in the distribution of enzyme after correcting for the correlation between lignin and cellulose. For the first time, colocalisation analysis was able to quantify the spatial distribution of amenable and recalcitrant sites in relation to the histochemistry of cellulose and lignin. This study will contribute to understanding the role of pretreatment in enzymatic hydrolysis of recalcitrant softwood biomass.

Journal of Chemical Technology & Biotechnology, 2016