Showing papers in "Current Science in 1999"

Solid state fermentation for the production of industrial enzymes

Abstract: Enzymes are among the most important products. obtained for human needs through microbial sources. A large number of industrial processes in the areas of industrial, environmental and food biotechnology utilize enzymes at some stage or the other. Current developments in biotechnology are yielding new applications for enzymes. Solid state fermentation (SSF) holds tremendous potential for the production of enzymes. Tt can be of special interest in those processes where the crude fermented products may be used directly as enzyme sources. This review focuses on the production of various industrial enzymes by SSF processes. Following a brief discussion of the micro-organisms and the substrates used in SSF systems, and aspects of the design of fermenter and the factors affecting production of enzymes, an illustrative survey is presented on various individual groups of enzymes such as cellulolytic, pectinolytic, ligninolytic, amylolytic and lipolytic enzymes, etc.

Reactive oxygen species: oxidative damage and pathogenesis

Abstract: Reactive oxygen species (ROS) such as O2–, H2O2 and OH are highly toxic to cells. Cellular antioxidant enzymes, and the free-radical scavengers normally protect a cell from toxic effects of the ROS. However, when generation of the ROS overtakes the antioxidant defense of the cells, oxidative damage of the cellular macromolecules (lipids, proteins, and nucleic acids) occurs, leading finally to various pathological conditions. ROS-mediated lipid peroxidation, oxidation of proteins, and DNA damage are well-known outcomes of oxygen-derived free radicals, leading to cellular pathology and ultimately to cell death. The mechanism of ROS-mediated oxidative damage of lipids, proteins, and DNA has been extensively studied. The site-specific oxidative damage of some of the susceptible amino acids of proteins is now regarded as the major cause of metabolic dysfunction during pathogenesis. ROS have also been implicated in the regulation of at least two well-defined transcription factors which play an important role in the expression of various genes encoding proteins that are responsible for tissue injury. One of the significant benefits of the studies on ROS will perhaps be in designing of a suitable antioxidant therapy to control the ROS-mediated oxidative damage, and the disease processes.

Microbial production of biosurfactants and their importance

Abstract: A large variety of microorganisms produce potent surface-active agents, biosurfactants, which vary in their chemical properties and molecular size. While the low molecular weight surfactants are often glycolipids, the high molecular weight surfactants are generally either polyanionic heteropolysaccharides containing covalently-linked hydrophobic side chains or complexes containing both polysaccharides and proteins. The yield of the biosurfactant greatly depends on the nutritional environment of the growing organism, The enormous diversity of biosurfactants makes them an interesting group of materials for application in many areas such as agriculture, public health, food, health care, waste utilization, and environmental pollution control such as in degradation of hydrocarbons present in soil.

Persistence in nonequilibrium systems

Abstract: THE problem of persistence in spatially extended nonequilibrium systems has recently generated a lot of interest both theoretically and experimentally. Persistence is simply the probability that the local value of the fluctuating nonequilibrium field does not change sign up to time t. It has been studied in various systems, including several models undergoing phase separation, the simple diffusion equation with random initial conditions, several reaction diffusion systems in both pure and disordered environments, fluctuating interfaces, Lotka–Volterra models of population dynamics, and granular media. The precise definition of persistence is as follows. Let φ(x, t) be a nonequilibrium field fluctuating in space and time according to some dynamics. For example, it could represent the coarsening spin field in the Ising model after being quenched to low temperature from an initial high temperature. It could also be simply a diffusing field starting from random initial configuration or the height of a fluctuating interface. Persistence is simply the probability P0(t) that at a fixed point in space, the quantity sgn[φ(x, t) – 〈φ(x, t)〉] does not change up to time t. In all the examples mentioned above this probability decays as a power law P0(t) ~ t –θ at late times, where the persistence exponent θ is usually nontrivial. In this article, we review some recent theoretical efforts in calculating this nontrivial exponent in various models and also mention some recent experiments that measured this exponent. The plan of the paper is as follows. We first discuss the persistence in very simple single variable systems. This makes the ground for later study of persistence in more complex many-body systems. Next, we consider many-body systems such as the Ising model and discuss where the complexity is coming from. We follow it up with the calculation of this exponent for a simpler manybody system namely diffusion equation and see that even in this simple case, the exponent θ is nontrivial. Next, we show that all these examples can be viewed within the general framework of the ‘zero crossing’ problem of a Gaussian stationary process (GSP). We review the new results obtained for this general Gaussian problem in various special cases. Finally, we mention the emerging new directions towards different generalizations of persistence. We start with a very simple system namely the onedimensional Brownian walker. Let φ(t) represent the position of a 1-D Brownian walker at time t. This is a single-body system in the sense that the field φ has no x dependence but only t dependence. The position of the walker evolves as,

Biogas production technology : an indian perspective

Abstract: Biogas technology provides an alternate source of energy in rural India, and is hailed as an archetypal appropriate technology that meets the basic need for cooking fuel in rural areas. Using local resources, viz. cattle waste and other organic wastes, energy and manure are derived. Realization of this potential and the fact that India supports the largest cattle wealth led to the promotion of National Biogas Programme in a major way in the late 1970s as an answer to the growing fuel crisis. Biogas is produced from organic wastes by concerted action of various groups of anaerobic bacteria. An attempt has been made in this review on the work done by our scientists in understanding the microbial diversity in biogas digesters, their interactions, factors affecting biogas production, alternate feedstocks, and uses of spent slurry.

Fluoride contamination status of groundwater in Karnataka

Abstract: Abnormal level of fluoride in phreatic groundwater causes serious health hazards in humans and physiological damages in plants. This study showed that occurrence of fluoride is highly sporadic and localized in eastern and southeastern Karnataka and the concentration of fluoride varies from 1 to 7.4 mg/l. The geological strata near the wells influence the fluoride content in phreatic groundwater. Effective and cheap methods of defluoridation are few and hence biological defluoridation may be the best alternative to the conventional methods.

Patterns of butterfly, bird and tree diversity in the Western Ghats

Abstract: We censused butterfly assemblages of the Western Chats of India in 15 localities and 8 vegetation types during 67 transects, each 600 m long, and traversed in one hour. The natural vegetation types had relatively high diversities compared to human impacted vegetation types such as scrub/savanna and grasslands. The home gardens and paddy fields had very distinctive species composition, coupled with very low levels of beta diversity. Their constituent species were more widespread. Comparison of these patterns with those found amongst trees and birds reported in similar studies threw up interesting parallels as well as contrasts. Species dissimilarity in evergreen vegetation types was high for trees and butterflies, but low for birds. Bird and butterfly assemblages in monoculture tree plantations had low species richness, less distinctiveness and high levels of dissimilarity, being comprised of rather widespread species. However, on the whole there was little relation between taxonomic groups and vegetation types across diversity parameters, There could be important implications of these patterns of diversity dispersion and their co-variation across taxonomic groups for assigning conservation priorities. We emphasize the need for classifying the landscape, both natural and manmade, on the basis of structural vegetation types, followed by stratified sampling of multiple groups of organisms for monitoring the status of and designing conservation strategy for biodiversity.

On growth and fluctuation of Indian foodgrain production

Abstract: We have analysed the variation of all-India foodgrain production over the last four decades to assess the typical magnitude of year-to-year fluctuation. This has shown that the magnitude of the variation between the foodgrain production in 1996 and 1997 is by no means unusual for normal monsoon years and such fluctuations should not have a large impact on GDP if the management of the economy allows for this natural fluctuation, Much larger year-to-year changes are expected for years with large anomalies in monsoon rainfall. The problems of sustaining the growth rate in irrigated areas and enhancing that of rainfed areas are addressed. It is suggested that to attain adequate growth rates for sustaining the per capita availability, a genuinely interdisciplinary approach is required with active participation of the farmers in identifying the optimal strategies.