Saurabh Sudha Dhiman

Characterization of statistically produced xylanase for enrichment of fruit juice clarification process

Critical factors for xylanase production of Bacillus stearothermophilus under batch fermentation and for clarification of citrus fruit juice using this xylanase were optimized through central composite design of response surface methodology. Statistical approach resulted in an increase of 1.19-fold in xylanase yield over conventional method. Model equation for juice clarification included independent variables viz. temperature, incubation time and enzyme dose to study the dependent variables such as yield, acidic neutrality and filterability etc. Coefficient of determination, R(2) for enzyme production model and for different juice properties were in accordance with the linearity of the model. On the basis of the contour plots the optimum enzyme dose was 12.5 IU/g of xylanase. Enzymatic treatment has resulted in the improvement of twofold in the release of reducing sugars and 52.97% in juice yield, whereas 35.34% reduction in turbidity was observed.

Short communicationOrganoiodine (III)-mediated synthesis of 3-aryl/heteroaryl-5,7-dimethyl-1,2,4-triazolo[4,3-c]pyrimidines as antibacterial agents

Synthesis of 12 new 3-aryl/heteroaryl-5,7-dimethyl-1,2,4-triazolo[4,3-c]pyrimidines (3a-l) has been accomplished by the oxidation of pyrimidinylhydrazones (2a-l) of various aryl/heteroaryl aldehydes using 1.1equiv. of iodobenzene diacetate (IBD) in dichloromethane. All the compounds 3a-l tested in vitro for their antibacterial activity against two Gram-positive bacteria namely, Bacillus subtilis, Bacillus stearothermophilus and two Gram-negative bacteria Pseudomonas putida, Escherichia coli. Two compounds, namely 3-(2,4-dichlorophenyl)-5,7-dimethyl-1,2,4-triazolo [4,3-c]pyrimidine (3j) and 3-(4-hydroxy-2-methoxyphenyl)-5,7-dimethyl-1,2,4-triazolo[4,3-c]pyrimidine (3l) were found to be equipotent or more potent than the commercially available antibiotics (chloramphenicol and streptomycin).

Bleach-boosting effect of crude xylanase from Bacillus stearothermophilus SDX on wheat straw pulp

Pretreatment of wheat straw pulp using cellulase-free xylanase produced from Bacillus stearothermophilus SDX at 60°C for 120min resulted in 4.75% and 22.31% increase in brightness and whiteness, respectively. Enzyme dose of 10U/g of oven dried pulp at pH 9 decreased the kappa number and permanganate number by 7.14% and 5.31%, respectively. Further chlorine dioxide and alkaline bleaching sequences (CDED(1)D(2)) resulted in 1.76% and 3.63% increase in brightness and whiteness, respectively. Enzymatic prebleaching of pulp decreased 20% of chlorine consumption without any decrease in brightness. Improvement in various pulp properties like viscosity, burst factor, burstness, breaking length, double fold, gurley porosity, tear factor, and tearness were also observed after bleaching of xylanase treated wheat straw pulp.

Biologically active macrocyclic complexes derived from diaminonaphthalene and glyoxal: Template synthesis and spectroscopic approach

A novel series of complexes of the type [M(C24H16N4)X2]; where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X = Cl− 1, , CH3COO− 1 has been synthesized by template condensation of 1,8-diaminonaphthalene and glyoxal in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, electronic, NMR, infrared and far infrared spectral studies. The low value of molar conductance indicates them to be non-electrolytes. On the basis of various studies a distorted octahedral geometry may be proposed for all of these complexes. These metal complexes were also tested for their in vitro antibacterial and antifungal activities to assess their inhibiting potential.

Synthetic, Structural and Biological Studies of Organotin(IV) Complexes of Schiff Bases Derived from Pyrrol-2-carboxaldehyde

Some new organotin(IV) complexes having general formulae R2MCl[L] and R2M[L]2 were synthesized by the reactions of Me2MCl2 with Schiff bases [5-Mercapto-4-(pyrrolcarboxalideneamino)-s-triazole, 5-Mercapto-3-methyl-4-(2-pyrrolcarboxalideneamino)- s-triazole, 3-Ethyl-5-mercapto-4-(2-pyrrolcarboxalideneamino)-s-triazole] in 1:1 and 1:2 molar ratios. All of the compounds were characterized by elemental analysis, molar conductance, IR, UV, 1H, 13C and 119Sn NMR spectral studies. The IR and 1H NMR spectral data suggest the involvement of azomethine nitrogen in coordination with the central metal atom. With the help of the above-mentioned spectral studies, penta and hexacoordinated environments around the central metal atoms in the 1:1 and 1:2 complexes, respectively, have been proposed. Finally, the free ligands and their metal complexes were tested in vitro against some pathogenic bacteria and fungi to assess their antimicrobial properties.

Spectral studies and antimicrobial activities of organosilicon(IV) and organotin(IV) complexes of nitrogen and sulfur donor Schiff bases derived from 4-amino-5-mercapto-3-methyl-s-triazole

Some new organosilicon(IV) and organotin(IV) complexes formulated as R2SiCl[L1], R2SiCl[L2], R2Si[L1]2, R2Si[L2]2, R2SnCl[L1], R2SnCl[L2], R2Sn[L1]2, and R2Sn[L2]2 have been synthesized by the reactions of Me2SiCl2 and Me2SnCl2 with Schiff bases in 1:1 and 1:2 molar ratios. L1 [2-(chlorobenzylidineamino)-5-mercapto-3-methyl-s-triazole] and L2[4-(flourobenzylidineamino)-5-mercapto-3-methyl-s-triazole] have been synthesized by the condensation of 2-chlorobenzaldehyde and 4-flourobenzaldehyde with 4-amino-5-mercapto-3-methyl-s-triazole. Newly synthesized organosilicon and organotin complexes have been characterized by elemental analysis, molar conductance measurements, spectral studies, including UV, IR, 1H, 13C, 29Si, and 119Sn NMR. The nature of these complexes is non-electrolytic. With the help of these techniques, trigonal bipyramidal and octahedral geometries are proposed for the newly synthesized complexes. The biological activity of these complexes against various bacteria and fungi has been investiga...

Antibacterial and antifungal studies of macrocyclic complexes of trivalent transition metal ions with their spectroscopic approach

A new series of complexes of the type [M(C24H16N4)X]X2, where M = Cr(III), Fe(III), and Mn(III), X = Cl−, NO3−, and CH3COO−, has been synthesized by template condensation of 1,8-diaminonaphthalene and glyoxal in the presence of trivalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analysis, conductance measurements, magnetic measurements, and electronic, NMR, IR, and mass spectral studies. On the basis of these studies, a five-coordinate square pyramidal geometry for all of these complexes has been proposed. All the synthesized metal complexes were also tested for their in vitro antimicrobial activities against some bacterial strains, viz. Bacillus subtilis, Bacillus stearothermophilus (gram-positive bacteria), Escherichia coli, and Pseudomonas putida (gram-negative bacteria), and some fungal strains, viz. Aspergillus flavus and Aspergillus niger. The results obtained were compared with standard antibiotics: chloramphenicol, streptomycin, and the antifungal drug cyclohexamide. Some of the tested complexes showed remarkable antimicrobial activities.

Pectinases of Thermophilic Microbes

Represented by archeal, bacterial, and fungal species, thermophilic organisms have been isolated from all types of terrestrial and marine hot environment. Pectinase from these organisms (thermophilic pectinase) developed unique structure–function properties of high thermostability and optimal activity at higher temperature. The advantage of using thermostable enzymes for various industrial applications is of course the intrinsic thermostability, and hence low activity losses during the raw material pretreatment at the elevated temperatures. Industrial applications of thermophilic pectinolytic enzyme have drawn a great deal of attention for use as biocatalysts because most of the industrial processes are carried out at higher temperature zone. Their potential to carry out myriads of biochemical reactions even at stringent conditions makes their use eco-friendly and best alternative to polluting chemical technologies. The role of acidic pectinases in extraction and clarification of fruit juices is well established. Recently, these have emerged as suitable candidate for biobleaching of wood pulp, desizing and bioscouring of cotton, degumming of plant fibers and biomass conversion, etc.