Amylases that are active under acidic conditions (pH <6), at higher temperatures (>70 degrees C) and have less reliance on Ca(2+) are required for starch hydrolysis. The alpha-amylase gene of Bacillus licheniformis MTCC 6598 was cloned and expressed in Escherichia coli BL21. The calcium-binding site spanning amino acid residues from 104 to 200 in the loop regions of domain B and D430 in domain C of amylase were changed by site-directed mutagenesis and the resultant mutant amylases were analyzed. Calcium-binding residues, N104, D161, D183, D200 and D430, were replaced with D104 and N161, N183, N200 and N430, respectively. Mutant amylase with N104D had a slightly decreased activity at 30 degrees C but a significantly improved specific activity at pH 5 and 70 degrees C, which is desirable character for a food enzyme. The amylase mutants with D183N or D200N lost all activity while the mutant amylase with D161N retained its activity at 30 degrees C but had significantly less activity at 70 degrees C. On the other hand, the activity of the mutant amylase with D430N was not changed at 30 degrees C but had an improved activity at 70 degrees C.
An endo-1,4-β-xylanase gene, xylcg, was cloned from Chaetomium globosum and successfully expressed in Escherichia coli. The complete gene of 675 bp was amplified, cloned into the pET 28(a) vector, and expressed. The optimal conditions for the highest activity of the purified recombinant XylCg were observed at a temperature of 40 °C and pH of 5.5. Using oat-spelt xylan, the determined K m, V max, and k cat/K m values were 0.243 mg ml⁻¹, 4,530 U mg⁻¹ protein, and 7,640 ml s⁻¹ mg⁻¹, respectively. A homology model and sequence analysis of XylCg, along with the biochemical properties, confirmed that XylCg belongs to the GH11 family. Rice straw pretreated with XylCg showed 30 % higher conversion yield than the rice straw pretreated with a commercial xylanase. Although xylanases have been characterized from fungal and bacterial sources, C. globosum XylCg is distinguished from other xylanases by its high catalytic efficiency and its effectiveness in the pretreatment of lignocellulosic biomass.
Automatic person identification from ear images is an active field of research within the biometric community. Similar to other biometrics such as face, iris and fingerprints, ear also has a large amount of specific and unique features that allow for person identification. In this current worldwide outbreak of COVID-19 situation, most of the face identification systems fail due to the mask wearing scenario. The human ear is a perfect source of data for passive person identification as it does not involve the cooperativeness of the human whom we are trying to recognize and the structure of ear does not change drastically over time. Acquisition of a human ear is also easy as the ear is visible even in the mask wearing scenarios. Ear biometric system can complement the other biometric systems in automatic human recognition system and provides identity cues when the other system information is unreliable or even unavailable. In this work, we propose a six layer deep convolutional neural network architecture for ear recognition. The potential efficiency of the deep network is tested on IITD-II ear dataset and AMI ear dataset. The deep network model achieves a recognition rate of 97.36% and 96.99% for the IITD-II dataset and AMI dataset respectively. The robustness of the proposed system is validated in uncontrolled environment using AMI Ear dataset. This system can be useful in identifying persons in a massive crowd when combined with a proper surveillance system.
Neosartorya fischeri β-glucosidase (NfBGL595) is distinguished from other BGLs by its high turnover for p-nitrophenyl β-d-glucopyranoside (pNPG) and flavones.
An isolated gene from Neosartorya fischeri NRRL181 encoding a β-glucosidase (BGL) was cloned, and its nucleotide sequence was determined. DNA sequence analysis revealed an open reading frame of 1,467 bp, capable of encoding a polypeptide of 488 amino acid residues. The gene was over-expressed in Escherichia coli, and the protein was purified using nickel-nitrilotriacetic acid chromatography. The purified recombinant BGL showed a high level of catalytic activity, with V (max) of 886 μmol min(-1) mg-protein(-1) and a K (m) of 68 mM for p-nitrophenyl-β-D: -glucopyranoside (pNPG). The optimal temperature for enzyme activity was about 40°C, and the optimal pH was about 6.0. A homology model of N. fischeri BGL1 was constructed based on the X-ray crystal structure of Phanerochaete chrysosporium BGLA. Molecular dynamics simulation studies of the enzyme with the pNPG and cellobiose shed light on the unique substrate specificity of N. fischeri BGL1 only towards pNPG.
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