http://localhost:8080/xmlui/handle/123456789/2068 2026-05-26T11:22:21Z http://localhost:8080/xmlui/handle/123456789/4836 Title: Engineering of Corynebacterium glutamicum for xylitol production from lignocellulosic pentose sugars Authors: Dhar, K S; Wendisch, V F; Nampoothiri, K M Abstract: Xylitol is a non-fermentable sugar alcohol used as sweetener. Corynebacterium glutamicum ATCC13032 was metabolically engineered for xylitol production from the lignocellulosic pentose sugars xylose and arabinose. Direct conversion of xylose to xylitol was achieved through the heterologous expression of NAD(P)H-dependent xylose reductase (xr) gene from Rhodotorula mucilaginosa. Xylitol synthesis from arabinose was attained through polycistronic expression of l-arabinose isomerase (araA), d-psicose 3 epimerase (dpe) and l-xylulose reductase (lxr) genes from Escherichia coli, Agrobacterium tumefaciens and Mycobacterium smegmatis, respectively. Expression of xr and the synthetic araA-dpe-lxr operon under the control of IPTG-inducible Ptac promoter enabled production of xylitol from both xylose and arabinose in the mineral (CGXII) medium with glucose as carbon source. Additional expression of a pentose transporter (araTF) gene enhanced xylitol production by about four-fold compared to the parent strain. The constructed strain Cg-ax3 produced 6.7 ± 0.4 g/L of xylitol in batch fermentations and 31 ± 0.5 g/L of xylitol in fed-batch fermentations with a specific productivity of 0.28 ± 0.05 g/g cdw/h. The strain Cg-ax3 was also validated for xylitol production from pentose rich, acid pre-treated liquor of sorghum stover (SAPL) and the results were comparable in both SAPL (27 ± 0.3 g/L) and mineral medium (31 ± 0.5 g/L). 2016-07-20T00:00:00Z http://localhost:8080/xmlui/handle/123456789/4831 Title: Influence of aliovalent cation substitutions on the optical properties of In2Cu2O5 system Authors: Divya, S; Rao, P P; Sameera, S; Raj, A K V Abstract: The influence of aliovalent cation substitutions in In2Cu2O5 system on the optical properties has been investigated through the powder X-ray diffraction coupled with Rietveld analysis, UV–vis–NIR spectroscopy, scanning electron microscope attached with energy dispersive spectrometer. The aliovalent cation substitution affected the optical absorption of the system distinctly as the counter cation substitution of Sc3+ influences the crystal field environment of Cu2+ ions more dominantly than that of the direct substitution of Zn2+ ions. Consequently this allowed the red shift of the absorption edge pronouncedly in the case of Sc3+ substituted samples than that in the Zn2+ substituted ones. The key factor responsible for achieving the larger red shift in Sc3+ substituted sample is due to increased anion polarizability. The assessments of crystal field and tetragonality parameters corroborate the variation of charge transfer energies for the aliovalent cation substitutions. The modified absorption properties translated in enhancing the green chromacity and reflectance of the In2Cu2O5 system even better than the commercially available chromium oxide green (Cr2O3). 2016-11-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/4830 Title: Microbial assisted High Impact Polystyrene (HIPS) degradation Authors: Mohan, A J; Sekhar, V C; Bhaskar, T; Nampoothiri, K M Abstract: The efficacy of newly isolated Pseudomonas and Bacillus strains to degrade brominated High Impact Polystyrene (HIPS) was investigated. Viability of these cultures while using e-plastic as sole carbon source was validated through Triphenyl Tetrazolium Chloride (TTC). Four days incubation of HIPS emulsion with Bacillus spp. showed 94% reduction in turbidity and was 97% with Pseudomonas spp. Confirmation of degradation was concluded by HPLC, NMR, FTIR, TGA and weight loss analysis. NMR spectra of the degraded film revealed the formation of aliphatic carbon chain with bromine and its release. FTIR analysis of the samples showed a reduction in Csingle bondH, Cdouble bondO and Cdouble bondN groups. Surface changes in the brominated HIPS film was visualized through SEM analysis. Degradation with Bacillus spp showed a weight loss of 23% (w/w) of HIPS film in 30 days. 2016-08-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/4829 Title: Production and characterization of poly(3-hydroxy butyrate-co-3 hydroxyvalerate) (PHBV) by a novel halotolerant mangrove isolate Authors: Moorkoth, D; Nampoothiri, K M Abstract: A halophilic mangrove isolate identified by 16S rRNA sequence as a Bacillus spp. was found to be capable of using a broad range of carbon sources including monosaccharides (glucose and fructose), disaccharides (sucrose), pentoses (xylose and arabinose), various organic acids (acetic acid, propionic acid and octanoic acid) and even the acid pre-treated liquor (APL) of sugarcane trash, a lignocellulosic biomass, for growth and the production of polyhydroxyalkanoates (PHAs) such as poly(3-hydroxybutyrate, P3HB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV), and 4-hydroxyhexanoate, 4HHX). The study describes the innate ability of a wild-type culture for PHBV production by both propionate dependent and propionate independent pathways. The biopolymer was extracted and characterized physico-chemically. The PHBV yield from glucose was estimated to be 73% of biomass weight with a high 3-hydroxyvalerate fraction of 48 mol%. Thereafter, spherical homogenous PHBV nanoparticles of ∼164 nm size were prepared for future applications. 2016-02-01T00:00:00Z