Search Results (2)

The ability of Aspergillus niger strains to support citric acid production using solid-state fermentation of agricultural processing coproducts was examined in this review. Citric acid has been shown to have a number of commercial applications in the food and beverage industries. The A. niger strains capable of elevated citric acid production are known to contain genetic mutations that stimulate overproduction of the organic acid likely involving citric acid cycle reactions. The agricultural processing coproducts previously examined for their ability to support citric acid production by A. niger solid-state fermentation include fruit processing wastes, sugarcane bagasse, starch vegetable processing wastes and cereal grain processing coproducts. A comparison of citric acid production by A. niger strains using solid-state fermentation demonstrated that certain agricultural processing coproducts were more effective in supporting a high level of acid synthesis. In particular, fruit processing wastes, such as apple pomace, banana peels, grape pomace and orange peels, supported high levels of citric acid by the fungal strains following solid-state fermentation. On the other hand, processing coproducts of cereal grains, such as brans and ethanol processing coproducts, supported low levels of citric acid production by the A. niger strains using solid-state fermentation. It appeared that the cereal processing coproducts provided less available sugar content to support citric acid production by the fungal strains. It was concluded that the level of citric acid produced by the A. niger strains during solid-state fermentation was dependent on the sugar content of the agricultural processing coproduct utilized. Full article

The recent advances on the effects of microstructural refinement and various nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides obtained in the last few years in the allied laboratories at the University of Waterloo (Canada) and Military University of Technology (Warsaw, Poland) are critically reviewed in this paper. The research results indicate that microstructural refinement (particle and grain size) induced by ball milling influences quite modestly the hydrogen storage properties of simple metal and complex metal hydrides. On the other hand, the addition of nanometric elemental metals acting as potent catalysts and/or metal halide catalytic precursors brings about profound improvements in the hydrogen absorption/desorption kinetics for simple metal and complex metal hydrides alike. In general, catalytic precursors react with the hydride matrix forming a metal salt and free nanometric or amorphous elemental metals/intermetallics which, in turn, act catalytically. However, these catalysts change only kinetic properties i.e. the hydrogen absorption/desorption rate but they do not change thermodynamics (e.g., enthalpy change of hydrogen sorption reactions). It is shown that a complex metal hydride, LiAlH₄, after high energy ball milling with a nanometric Ni metal catalyst and/or MnCl₂ catalytic precursor, is able to desorb relatively large quantities of hydrogen at RT, 40 and 80 °C. This kind of behavior is very encouraging for the future development of solid state hydrogen systems. Full article