Karna Venkata Ramana

Effect of various carbon and nitrogen sources on cellulose synthesis by Acetobacter xylinum.

The effect of various carbon and nitrogen sources on cellulose membrane production by Acetobacter xylinum was evaluated. Among the carbon sources, sucrose, glucose and mannitol were found to be suitable for optimum levels of cellulose production. The strain was able to utilize a wide range of protein and nitrogen sources such as peptone, soybean meal, glycine, casein hydrolysate, and glutamic acid for cellulose synthesis. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of pellicle proteins (PP) revealed electrophoretic bands of molecular masses in the range of 116–20 kDa. Furthermore, the strain can be useful for the removal of various nitrogenous and carbon substrates present in waste waters.

Augmented properties of PVA hybrid nanocomposites containing cellulose nanocrystals and silver nanoparticles

PVA nanocomposites containing cellulose nanocrystals and silver nanoparticles have been prepared and their properties were investigated. Even though bacterial cellulose nanocrystals (BCNC) improved the mechanical properties of hydrophilic polymers like modulus and strength, they also contributed to increased brittleness. An attempt was made to reduce the brittleness of the films by incorporating Ag nanoparticles (AgNPs) along with BCNC. The AgNPs could form complexes with the hydroxyl groups of PVA and played the role of physical crosslinks, which makes them less hydrophilic and more ductile in nature. FTIR studies were used to confirm the interaction of AgNPs with PVA. The addition of AgNPs increased the elongation properties without compromising on other mechanical properties and at the same time it significantly reduced the moisture sorption also. Results of the study indicated that the combination of two different nanomaterials was highly effective in overcoming certain limitations of PVA–BCNC nanocomposites.

Hybrid HPMC nanocomposites containing bacterial cellulose nanocrystals and silver nanoparticles.

Hydroxypropyl methyl cellulose (HPMC) based hybrid nanocomposites reinforced with bacterial cellulose nanocrystals (BCNC) and silver nanoparticles (AgNPs) had been prepared and characterised. BCNC was capable of improving the tensile strength and modulus of HPMC, but they made the film more brittle. The addition of AgNPs along with BCNC, helped to regain some of the lost elongation properties without affecting other properties. Moisture sorption analysis proved that the hydrophilicity of the nanocomposite decreased considerably by the addition of these nanomaterials. Several mathematical models were also used to fit the experimental sorption results. A unique combination of two nanomaterials was highly effective in overcoming certain limitations of nanocomposites which uses only one type of nanomaterial. This type of hybrid nanocomposites with superior properties is expected to be useful in eco-friendly food packaging applications.

Production of biogas from night soil at psychrophilic temperature.

Abstract Anaerobic digestion of night soil was carried out in a 25 l digester at 10°C using an adapted inoculum. Biogas production was studied at 20, 25, 30, 35 and 40 days hydraulic retention time. Digesters operated at 25 day hydraulic retention time produced 69·72 l biogas/kg VS/day with a methane content of 73·0%. Microbial counts and enzyme activities are also reported.