SummaryThe current knowledge of trehalose biosynthesis under stress conditions is incomplete and needs further research. Since trehalose finds industrial and pharmaceutical applications, enhanced accumulation of trehalose in bacteria seems advantageous for commercial production. Moreover, physiological role of trehalose is a key to generate stress resistant bacteria by metabolic engineering. Although trehalose biosynthesis requires few metabolites and enzyme reactions, it appears to have a more complex metabolic regulation. Trehalose biosynthesis in bacteria is known through three pathways – OtsAB, TreYZ and TreS. The interconnections of in vivo synthesis of trehalose, glycogen or maltose were most interesting to investigate in recent years. Further, enzymes at different nodes (glucose-6-P, glucose-1-P and NDP-glucose) of metabolic pathways influence enhancement of trehalose accumulation. Most of the study of trehalose biosynthesis was explored in medically significant Mycobacterium, research model Escherichia coli, industrially applicable Corynebacterium and food and probiotic interest Propionibacterium freudenreichii. Therefore, the present review dealt with the trehalose metabolism in these bacteria. In addition, an effort was made to recognize how enzymes at different nodes of metabolic pathway can influence trehalose accumulation.
There is anatomical evidence in cats and baboons of cells at the margin of area 17 which have callosal connections to corresponding points in the opposite hemisphere.The function of such a pathway has been studied in cats after one optic tract has been cut. The corresponding hemisphere now gives early visual responses only at the margin of area 17. Such responses can only be elicited by light stimuli near the vertical meridian of the visual field. These responses are abolished by cooling the corresponding points in the opposite hemisphere and by cutting the corpus callosum.This pathway appears to provide some functional union for the two halves of the visual field.
Cortical projection of the visual field on the albino rabbit's cortex has been investigated and compared with that in the pigmented rabbit. A lower magnification of the projection of the temporal visual streak (nasal visual field) in the albino rabbit is attributed to the absence of an area centralis-like organization of the retinal ganglion cells in the temporal visual streak in this animal. Cortical single units in the albino rabbit show a lesser variety in their receptive field organization than those in the pigmented rabbit.
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.
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.
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