Correlation of mass transfer coefficient and solute permeate flux in pervaporation of benzene-cyclohexane mixtures using a composite PVA membrane on PAN support

309-315Pervaporation of benzene-cyclohexane mixtures has been carried out in an agitated batch permeation cell (with vacuum maintained downstream) using a proprietary composite membrane of polyvinyl alcohol (PVA) on a porous polyacrylonitrile (PAN) support, at 298 K and 0.8 torr downstream pressure. Effect of operating parameters like feed solute concentration, CL0 and agitator speed, n on the overall solute permeate flux has been elaborately studied. Based on the experimental data, an attempt has been made to predict mass transfer coefficient and pervaporative mass transfer flux, from semi-empirical approach. The predictive equations for the two above mentioned design parameters are presented

Effect of carbon supply mode on biomass and lipid in CSMCRI's Chlorella variabilis (ATCC 12198)

CSIR-CSMCRI's Chlorella variabilis (ATCC 12198) was evaluated through autotrophic, mixotrophic and heterotrophic growth for lipid production. Autotrophic growth was assessed by providing sodium bicarbonate/ sodium carbonate/CO2 (air in a medium). Higher lipid productivity (115.94 mg L�1 d�1) with higher biomass productivity (724.98 mg L�1 d�1) of this strain was attained through bicarbonate and CO2 sequestration in a photobioreactor. Ability to regulate the pH in favorable bicarbonate/carbonate ratio showed its potential in alkaline effluent based carbon sequestration system for biofuel generation. The simultaneous study was also conducted to understand the effect of elevated CO2 (0.4, 1 and 1.2 g L�1) in air on the culture to assess adaptation, growth and lipid in the closed chamber conditions. It was observed that CO2 sequestration by the microalgae from the CO2 enriched environment was optimum at 1 g L�1 C. variabilis adapted to comparatively higher CO2 (1 g L�1) but grew better in low CO2 (0.4 g L�1). It was also observed that the growth, lipid content and fatty acid composition was significantly affected by CO2 supply strategies. The effect of intermittently added sodium bicarbonate at different pH on microalgal lipid content and composition of fatty acids was observed which could affect the quality of biodiesel. The effect on fatty acid composition was observed in response to carbon supply mode during the microalgal growth at different pH dictating the properties of biodiesel

Prediction of vapour-liquid pseudo-equilibrium data for pervaporation of benzene-cyclohexane system

290-293In pervaporation operation pore diffusion model predicts that a vapour-liquid pseudo-equilibrium exists between the solute concentration in vapour and liquid phases during its flow through the pores of the membrane. In the present investigation, using pore diffusion model an attempt has been made to predict a semi-empirical vapour-liquid equilibrium relationship for benzene concentration in vapour and liquid inside the pore of the membrane while separating benzene-cyclohexane azeotropic mixture by pervaporation technique

Xylan glucuronic acid side chains fix suberin-like aliphatic compounds to wood cell walls

Wood is the most important repository of assimilated carbon in the biosphere, in the form of large polymers (cellulose, hemicelluloses including glucuronoxylan, and lignin) that interactively form a composite, together with soluble extractives including phenolic and aliphatic compounds. Molecular interactions among these compounds are not fully understood. We have targeted the expression of a fungal α-glucuronidase to the wood cell wall of aspen (Populus tremula L. × tremuloides Michx.) and Arabidopsis (Arabidopsis thaliana (L.) Heynh), to decrease contents of the 4-O-methyl glucuronopyranose acid (mGlcA) substituent of xylan, to elucidate mGlcA's functions. The enzyme affected the content of aliphatic insoluble cell wall components having composition similar to suberin, which required mGlcA for binding to cell walls. Such suberin-like compounds have been previously identified in decayed wood, but here, we show their presence in healthy wood of both hardwood and softwood species. By contrast, γ-ester bonds between mGlcA and lignin were insensitive to cell wall-localized α-glucuronidase, supporting the intracellular formation of these bonds. These findings challenge the current view of the wood cell wall composition and reveal a novel function of mGlcA substituent of xylan in fastening of suberin-like compounds to cell wall. They also suggest an intracellular initiation of lignin–carbohydrate complex assembly