Publications by authors named "Kumar Raviranjan"

4 Publications

  • Page 1 of 1

Production, partial purification and characterization of a proteoglycan bioemulsifier from an oleaginous yeast.

Bioprocess Biosyst Eng 2020 Oct 14;43(10):1747-1759. Epub 2020 May 14.

Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal, Kharagpur, 721302, India.

In this study, Meyerozyma caribbica, an indigenously isolated oleaginous yeast, produced in media containing glucose a bioemulsifier that was partially characterized as a proteoglycan based on preliminary analysis. Optimization of carbon:nitrogen (C:N) ratio revealed 30:1 as the suitable ratio for enhanced production. Apart from higher emulsification activity (E: 70-80%), this molecule showed strong emulsion stability over a wide range of pH (2.0-9.0), salinity (0.05%-10%, w/v) and temperature (- 80 °C to + 50 °C). The current study emphasizes on the determination of critical media parameters for improved and stable bioemulsifier production coupled with partial characterization and identification of the molecule. Thus, a proteoglycan-based bioemulsifier with such a stable emulsifying property can serve as a versatile and potential component in food, cosmetics and pharmaceutical formulations.
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http://dx.doi.org/10.1007/s00449-020-02361-1DOI Listing
October 2020

Combinatorial action of Grainyhead, Extradenticle and Notch in regulating Hox mediated apoptosis in Drosophila larval CNS.

PLoS Genet 2017 Oct 12;13(10):e1007043. Epub 2017 Oct 12.

Laboratory of Drosophila Neural Development, Centre for DNA Fingerprinting and Diagnostics (CDFD), Tuljaguda Complex, Nampally, Hyderabad, India.

Hox mediated neuroblast apoptosis is a prevalent way to pattern larval central nervous system (CNS) by different Hox genes, but the mechanism of this apoptosis is not understood. Our studies with Abdominal-A (Abd-A) mediated larval neuroblast (pNB) apoptosis suggests that AbdA, its cofactor Extradenticle (Exd), a helix-loop-helix transcription factor Grainyhead (Grh), and Notch signaling transcriptionally contribute to expression of RHG family of apoptotic genes. We find that Grh, AbdA, and Exd function together at multiple motifs on the apoptotic enhancer. In vivo mutagenesis of these motifs suggest that they are important for the maintenance of the activity of the enhancer rather than its initiation. We also find that Exd function is independent of its known partner homothorax in this apoptosis. We extend some of our findings to Deformed expressing region of sub-esophageal ganglia where pNBs undergo a similar Hox dependent apoptosis. We propose a mechanism where common players like Exd-Grh-Notch work with different Hox genes through region specific enhancers to pattern respective segments of larval central nervous system.
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http://dx.doi.org/10.1371/journal.pgen.1007043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5667929PMC
October 2017

Role of Homothorax in region specific regulation of Deformed in embryonic neuroblasts.

Mech Dev 2015 Nov 25;138 Pt 2:190-197. Epub 2015 Sep 25.

Laboratory of Drosophila Neural Development, Centre for DNA Fingerprinting and Diagnostics (CDFD), 4-1-714, Tuljaguda Complex, Nampally, Hyderabad-500001, India. Electronic address:

The expression and regulation of Hox genes in developing central nervous system (CNS) lack important details like specific cell types where Hox genes are expressed and the transcriptional regulatory players involved in these cells. In this study we have investigated the expression and regulation of Drosophila Hox gene Deformed (Dfd) in specific cell types of embryonic CNS. Using Dfd neural autoregulatory enhancer we find that Dfd autoregulates itself in cells of mandibular neuromere. We have also investigated the role of a Hox cofactor Homothorax (Hth) for its role in regulating Dfd expression in CNS. We find that Hth exhibits a region specific role in controlling the expression of Dfd, but has no direct role in mandibular Dfd neural autoregulatory circuit. Our results also suggest that homeodomain of Hth is not required for regulating Dfd expression in embryonic CNS.
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http://dx.doi.org/10.1016/j.mod.2015.09.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4678145PMC
November 2015

A highly thermostable alkaline cellulase-free xylanase from thermoalkalophilic Bacillus sp. JB 99 suitable for paper and pulp industry: purification and characterization.

Appl Biochem Biotechnol 2010 Nov 14;162(7):2049-57. Epub 2010 May 14.

Department of Biotechnology, Gulbarga University, Karnataka, India.

A highly thermostable alkaline xylanase was purified to homogeneity from culture supernatant of Bacillus sp. JB 99 using DEAE-Sepharose and Sephadex G-100 gel filtration with 25.7-fold increase in activity and 43.5% recovery. The molecular weight of the purified xylanase was found to be 20 kDA by SDS-PAGE and zymogram analysis. The enzyme was optimally active at 70 °C, pH 8.0 and stable over pH range of 6.0-10.0.The relative activity at 9.0 and 10.0 were 90% and 85% of that of pH 8.0, respectively. The enzyme showed high thermal stability at 60 °C with 95% of its activity after 5 h. The K (m) and V (max) of enzyme for oat spelt xylan were 4.8 mg/ml and 218.6 µM min(-1) mg(-1), respectively. Analysis of N-terminal amino acid sequence revealed that the xylanase belongs to glycosyl hydrolase family 11 from thermoalkalophilic Bacillus sp. with basic pI. Substrate specificity showed a high activity on xylan-containing substrate and cellulase-free nature. The hydrolyzed product pattern of oat spelt xylan on thin-layer chromatography suggested xylanase as an endoxylanase. Due to these properties, xylanase from Bacillus sp. JB 99 was found to be highly compatible for paper and pulp industry.
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http://dx.doi.org/10.1007/s12010-010-8980-6DOI Listing
November 2010
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