Biomedical subjects

V C Kalia

Publications and source records attributed to V C Kalia.

2 recordsLinked to original sources

PubMed2003

Polyhydroxyalkanoates: an overview.

Polyhydroxyalkanoates have gained major importance due to their structural diversity and close analogy to plastics. These are gaining more and more importance world over. Different sources (natural isolates, recombinant bacteria, plants) and other methods are being investigated to exert more control over the quality, quantity and economics of poly(3-hydroxybutyrate) (PHB) production. Their biodegradability makes them extremely desirable substitutes for synthetic plastics. The PHB biosynthetic genes phbA, phbB and phbC are clustered and organized in one phbCAB operon. The PHB pathway is highly divergent in the bacterial genera with regard to orientation and clustering of genes involved. Inspite of this the enzymes display a high degree of sequence conservation. But how similar are the mechanisms of regulation of these divergent operons is as yet unknown. Structural studies will further improve our understanding of the mechanism of action of these enzymes and aid us in improving and selecting better candidates for increased production. Metabolic engineering thereafter promises to bring a feasible solution for the production of "green plastic".

Bacteria↗

PubMed1998

Effect of some physiological factors on nitrogenase activity and nitrogenase mediated hydrogen evolution by mixed microbial culture.

Fermentative H2 evolution, nitrogenase activity (acetylene reduction) and nitrogenase mediated H2 evolution was studied in free cells of mixed microbial population of H2 producers. At 3% glucose level, the cells produced 8.35 l H2/mol glucose utilized. The role of nitrogenase system in H2 generation was evident by derepressed nitrogenase activity (0.46 nmoles C2H4 produced/mg protein/h) under defined in vitro conditions. For maximum expression of the activity, the cells required preactivation under anaerobic conditions by incubating at 40 degrees C for 20-24 h with 0.2% glucose in the culture medium. At an O2 level of more than 0.25%, the acetylene reduction activity decreased significantly and could not be detected at a level of 20%. Nitrogenase activity development was higher at acetylene: inoculum ratio between 4.2-6.25. H2 evolution was lower when the mixed cells were incubated under an atmosphere of 10% C2H2 and 5% CO gas. This decrease in H2 evolution was also evident at 2.5-6.5 mM NaNO3 and KNO3 concentrations in the liquid culture medium thus establishing more than 50% H2 evolution through nitrogenase.

Acetylene↗