Neelam Garg

One-step purification and characterization of cellulase-free xylanase produced by alkalophilic Bacillus subtilis ash

The present study describes the one-step purification and characterization of an extracellular cellulase-free xylanase from a newly isolated alkalophilic and moderately thermophilic strain of Bacillus subtilis ASH. Xylanase was purified to homogeneity by 10.5-fold with ~43% recovery using ion-exchange chromatography through CM-Sephadex C-50. The purified enzyme revealed a single band on SDS-PAGE gel with a molecular mass of 23 kDa. It showed an optimum pH at 7.0 and was stable over the pH range 6.0-9.0. The optimum temperature for enzyme activity was 55 oC. The purified xylanase did not lose any activity up to 45 oC, however, it retained 80% and 51% of its activity after pre-incubation at 55 oC and 60 oC, respectively. The enzyme obeyed Michaelis-Menton kinetics towards birch wood xylan with apparent Km 3.33 mg/ml and Vmax 100 IU/ml. The enzyme was strongly inhibited by Hg2+ and Cu2+ while enhanced by Co2+ and Mn2+. The purified enzyme could be stored at 4 oC for six weeks without any loss of catalytic activity. The faster and economical purification of the cellulase-free xylanase from B. subtilis ASH by one-step procedure together with its appreciable stability at high temperature and alkaline pH makes it potentially effective for industrial applications.

Bioremediation of Heavy Metals by Microbes

Heavy metals are naturally present in the soil, but higher concentration of these elements is harmful to plants, animals, and humans. Prolonged exposure of such heavy metals can have deleterious health effects on human life. Bioremediation of these heavy metals like As, Cd, Cr, Hg, Ni, Hg, and Zn can be done by either plants or microorganisms or by the combination of two. In this chapter emphasis has been given to its microbial methods. There are certain disadvantages associated with physicochemical methods of remediation; thus bioremediation is arising as alternative to these methods. It is an environment friendly approach because it is achieved via natural processes. In this chapter efforts have been made to give brief introduction of available physicochemical and biological methods of heavy metal remediation. Bioremediation by bacteria and fungi is discussed in detail.

Fortified Foods and Medicinal Plants as Immunomodulators

There is a strong consensus that nutrition plays an important role in modulating the immune system which needs adequate supply of nutrients to function properly. The complexity of the immune system supports this idea because its optimal functioning involves a variety of biological activities including energy metabolism, production of proteins, cell division, and proliferation. Important micronutrients to the immune function include vitamins A, C, E, and B6, folate, iron, zinc, and selenium. Other nutrients mentioned as playing a role in immune function include beta-carotene (a precursor to vitamin A), vitamin B12, and vitamin D. On the other hand, overdoses for activation of the immune system can lead to detrimental effects such as chronic inflammation or autoimmune diseases. In some individuals with allergies, a normally harmless material can be mistaken as an antigen. Immune functions are responsible to protect the body against attack by pathogens or cancer cells and thus play a vital role for health and well-being. However, the immune functions are disturbed by malnutrition, aging, physical and mental stress, or undesirable lifestyle. Therefore, ingestion of foods with immune-modulating activities is considered an efficient way to reduce the risk of infections or cancer and to prevent the immune function from declining.

Irradiation: A Technique for Microbial Decontamination of Medicinal Plants

Nature has bestowed on us a very rich botanical wealth and a large number of diverse types of plants growing in different parts of the world. These plants are used for cosmetics, spices, herbs, and food supplements and referred to as “medicinal plants” in this chapter. Due to their nutritional, antioxidant, antimicrobial, and medicinal properties, these plants can be exploited for widespread applications. Many medicinal plants are grown in developing countries where sanitation and handling practices may not be satisfactory. Plant materials are exposed to microbial contaminants during their cultivation, harvest, processing, storage, distribution, and sale which exert a significant impact on overall quality and shelf life of the products. Therefore, decontamination of medicinal plants is necessary to eliminate pathogenic and reduce the number of spoilage microorganisms. A number of different techniques including fumigation, steaming, and irradiation have been used for microbial decontamination with varying degrees of success. Among all these techniques, irradiation has become the most important technique. In this article, various techniques of decontamination of medicinal plants and regulatory aspects of irradiation are discussed.

Listeria Species: Reemerging Pathogen in Drinking Water Utilities

Listeria monocytogenes is recognized worldwide as one of the most important foodborne pathogens of concern for the food industries. It is a ubiquitous microorganism, and it is commonly isolated from foods of animal origin, mainly meat and milk products, but a few Listeria outbreaks have occurred in which these pathogens have been isolated from water systems and implicated as source of infection. The bacteria are aerobic and facultative anaerobic and non-spore and non-capsule forming, with optimal growth temperature of between 30 °C and 37 °C. They can, however, grow and reproduce at temperatures between 0.4 °C and 45 °C and pH 4.5–9.6. In the present chapter, occurrence of Listeria spp. in ground, surface, and bottled drinking water along with survival of Listeria spp. in oligotrophic and copiotrophic environments and antibiotic susceptibility, molecular detection, pathogenicity, and virulence of Listeria spp. have been discussed in detail.

Crop residue degradation by fungi isolated from conservation agriculture fields under rice–wheat system of North-West India

PurposeIn North West-Indo Gangetic Plains (NW-IGP) of India in situ burning of crop residues is practiced by majority of farmers’ which deteriorates soil and environmental quality. Fungi have the potential for lignocellulose degradation and can be used for the in situ decomposition of crop residues. Lignocellulose degrading fungal spp. were isolated and evaluated for the activity of lignocellulolytic enzymes.MethodThe lignocellulose degrading fungi were isolated by appearance of zone on carboxy methyl cellulose (CMC) agar media and tannic acid (TA) media. Carboxy methyl cellulase, filter paperase, cellobiase, xylanase and laccase activity were estimated in submerged, as well as solid state fermentation using a mixture of rice and wheat straw in the ratio of 4:1. rice–wheat straw as substrate. The residue left after solid state fermentation was evaluated for carbon/nitrogen ratio, dry mass loss, and loss of cellulose, hemicellulose and lignin. Selected potential isolates were further tested in pot experiment for their effect on wheat plants. The interaction among isolates was also studied.ResultAfter primary screening, 19 out of a total of 72 fungal isolates were selected based on their enzymatic activity profile and potential to degrade lignocellulosic residues in submerged fermentation. Out of these 19 isolates, 11 were further selected based on their enzymatic secretions in solid state fermentation. All the 11 strains were identified morphologically. Four fungal isolates (RPW 1/3, RPW 1/6, RPWM 2/2 and RZWM 3/2) showed higher enzymatic activities and more loss of dry mass and cell wall constituents over the other isolates. These isolates were identified by ITS region sequencing as Aspergillus flavus, Aspergillus terreus, Penicillium pinophilum and Alternaria alternata.ConclusionThis study revealed that fungal isolates may be used for managing crop residues in conservation agriculture based rice–wheat system of NW-IGP to eliminate ill effects of residue burning.

Health Benefits of Trace Elements in Human Diseases

Microorganisms are found almost everywhere and they are extremely adaptable to harsh conditions and survive wherever they are. Microorganisms are exploited by biotechnologists in traditional fortified foods, dairy foods, beverage preparation, and in modern technologies based on genetic engineering. However, there are many pathogenic microbes which are harmful and can cause death in human, plants, and animals. Some chronic non-communicable diseases such as diarrhea and respiratory diseases are well known to be caused by harmful microbes. Trace elements show a number of biochemical and physiological functions. Fortification of foods with traces of essential elements such as selenium, zinc, chromium, copper, silicon, as well as iron, nickel, and vanadium can prevent many of communicable and non-communicable diseases. Human health has a vital relationship with the balance of essential trace elements for the healthy functioning of human body. Supplementation with trace elements should be carefully controlled. When given in quantities exceeding those required for accomplishing their biological functions, they will cause toxic effects. The dietary reference intakes provided by national regulatory agencies are guides to define intake, supplementation, and toxicity of trace elements for humans.

Microbes in Food and Health

Microbes in food and health / , Microbes in food and health / , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی