The effects of moderate-temperature aqueous butanol pretreatment of rice straw on several organic catalysts have been studied. Maximum delignification was obtained with an aromatic organic acid catalyst. Presoaking of straw in aqueous improved delignification, particularly in high solid-liquid rations. However, due to the difficulty of penetration of lignin into the solvent phase, an increase in the solid-liquid ratio appears to affect delignification. A two-stage catalytic solvent process involving presoaking at 80 degrees C followed by delignification at 120 degrees C resulted in 83% removal of lignin in aqueous-butanol, whereas 75% lignin removal was possible in ethanol. Higher reduction in the crystallinity was possible with etanol. Lignin produced by the solvent process offers desirable physical properties for polymer applications compared to Kraft lignin.
The biotransformation of acrylonitrile was investigated using thermophilic nitrilase produced from a new isolate Streptomyces sp. MTCC 7546 in both the free and immobilized state. Under optimal conditions,the enzyme converts nitriles to acids without the formation of amides.The whole cells of the isolate were immobilized in agar-agar and the beads so formed were evaluated for 25 cycles at 50 degrees C. The enzyme showed a little loss of activity during reuse. Seventy-one per cent of 0.5 M acrylonitrile was converted to acid at 6 h of incubation at a very low density of immobilized cells, while 100% conversion was observed at 3 h by free cells.
A new thermostable nitrilase-producing isolate identified as Streptomyces sp. MTCC 7546 has been studied extensively for the optimization of enzyme production operating in batch mode. The benzonitrile was observed as inducer of nitrilase production. The isolate showed maximum nitrilase production after 24 h of incubation at optimal conditions. The strain grows well on a variety of carbon sources and produces the nitrilase that catalyses the hydrolysis of nitriles to acids without formation of amides. The enzyme is mostly active against mono-and di-aliphatic nitriles (10 mmol L −1 ) at pH of 7.4 and at a temperature of 50 • C.
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