Ajar Nath Yadav

β-Propeller phytases: Diversity, catalytic attributes, current developments and potential biotechnological applications

Phytases are phosphatases which stepwise remove phosphates from phytic acid or its salts. β-Propeller phytase (BPPhy) belongs to a special class of microbial phytases that is regarded as most diverse, isolated and characterized from different microbes, mainly from Bacillus spp. BPPhy class is unique for its Ca2+-dependent catalytic activity, strict substrate specificity, active at neutral to alkaline pH and high thermostability. Numerous sequence and structure based studies have revealed unique attributes and catalytic properties of this class, as compared to other classes of phytases. Recent studies including cloning and expression and genetic engineering approaches have led to improvements in BPPhy which provide an opportunity for extended utilization of this class of phytases in improving animal nutrition, human health, plant growth promotion, and environmental protection, etc. This review describes the sources and diversity of BPPhy genes, biochemical properties, Ca2+ dependence, current developments in structural elucidation, heterogeneous expression and catalytic improvements, and multifarious applications of BPPhy.

Food waste: a potential bioresource for extraction of nutraceuticals and bioactive compounds

Food waste, a by-product of various industrial, agricultural, household and other food sector activities, is rising continuously due to increase in such activities. Various studies have indicated that different kind of food wastes obtained from fruits, vegetables, cereal and other food processing industries can be used as potential source of bioactive compounds and nutraceuticals which has significant application in treating various ailments. Different secondary metabolites, minerals and vitamins have been extracted from food waste, using various extraction approaches. In the next few years these approaches could provide an innovative approach to increase the production of specific compounds for use as nutraceuticals or as ingredients in the design of functional foods. In this review a comprehensive study of various techniques for extraction of bioactive components citing successful research work have been discussed. Further, their efficient utilization in development of nutraceutical products, health benefits, bioprocess development and value addition of food waste resources has also been discussed.

Hot springs of Indian Himalayas: potential sources of microbial diversity and thermostable hydrolytic enzymes

Microbial communities in hot springs at high elevations have been extensively studied worldwide. In this sense, the Indian Himalaya regions is valuable ecosystems for providing both the extreme ‘cold’ and ‘hot’ sites for exploring microbial diversity. In the present study, a total of 140 thermophilic bacteria were isolated from 12 samples collected from Manikaran and Yumthang hot springs of Indian Himalayas. The bacterial isolates were studied for phylogenetic profiling, growth properties at varying conditions and potential sources of extracellular thermostable hydrolytic enzymes such as protease, amylase, xylanase and cellulase. Based on production of extracellular hydrolases, 51 isolates from Manikaran (28) and Yumthang thermal springs (23) were selected and identified using 16S rRNA gene sequencing which included 37 distinct species of 14 different genera namely Anoxybacillus, Bacillus, Brevibacillus, Brevundimonas, Burkholderia, Geobacillus, Paenibacillus, Planococcus, Pseudomonas, Rhodanobacter, Thermoactinomyces, Thermobacillus, Thermonema and Thiobacillus. Out of 51 hydrolase producing bacteria, 24 isolates showed stability at wide range of temperature and pH treatments. In present investigation, three thermotolerant bacteria namely, Thermobacillus sp NBM6, Paenibacillus ehimensis NBM24 and Paenibacillus popilliae NBM68 were found to produced cellulase-free xylanase. These potential extracellular thermostable hydrolytic enzymes producing thermophilic bacteria have a great commercial prospect in various industrial, medical and agriculture applications.

Biodiversity of the Genus Penicillium in Different Habitats

Abstract Penicillium is a genus of ascomycetous fungi and has an important role in various natural processes. The wide and ubiquitous presence of the Penicillium species has been researched in several studies. According to a comprehensive literature analysis Penicillium is one of the most common fungi occurring in various environments such as soil, air, and extreme environments (temperature, salinity, water deficiency, and pH) and is also associated with plants and specific food products. Due to its huge diversity and existence in extreme environments there is great potential in using it for various environmental, biotechnological, and industrial applications. This chapter describes how to isolate and identify Penicillium species and its diversity in various habitats as well as insight in its selectivity.

Microbes in Termite Management: Potential Role and Strategies

Several control methods like physical, chemical, and biological are adopted to control termites in various localities. Biological control methods are eco-friendly and target-specific; hence they could represent a suitable alternative to chemical control methods. Microbial biological control is based on the use, and proper adjustment, of natural enemies via microbial organisms, such as bacteria, fungi, virus, and nematodes with the aim of suppression and management of insect populations. A broad range of species, from different groups of microbial organisms, have strong association with termites, and some have been recorded as parasites, including species currently used as commercial biological control agents.

Beneficial Plant-Microbes Interactions: Biodiversity of Microbes from Diverse Extreme Environments and Its Impact for Crop Improvement

Microbes are capable of colonizing the rhizosphere and phyllosphere as well as living inside the plant tissues as endophytes. The microbiomes associated with the crops have the ability to produce phytohormones (indoleacetic acid and gibberellic acid); solubilize (phosphorus, potassium and zinc) and bind nutrients, besides eliciting plant defence reactions against pathogens; and also help in plant growth under harsh environments. The biodiversity of plant growth-promoting (PGP) microbes have been illustrated by different genera and species and their mechanisms of action for the following different phyla of domain Archaea, Bacteria and Eukarya:Actinobacteria,Ascomycota,Bacteroidetes,Basidiomycota,Crenarchaeota,Euryarchaeota,Firmicutes andProteobacteria (α/β/γ/δ). This book chapter intends to present research results obtained so far concerning the application of beneficial microbes as PGP microbes and their potential biotechnological application to increase the plant growth and yields and soil health. The diverse range of activities as well as the number of microbes sorted out in different culture collections around the world, may provide an important resource to rationalize the use of chemical fertilizers in agriculture. There are many microbial species that act as PGP microbes, described in the literature as successful for improving plant growth and health. However, there is a gap between the mode of action/mechanism of the PGP microbes for plant growth and the role of the PGP microbes as biofertilizers. Hence, this book chapter bridges the gap mentioned and summarizes the mechanism of PGP microbes as biofertilizers for agricultural sustainability.

Psychrotrophic Microbiomes: Molecular Diversity and Beneficial Role in Plant Growth Promotion and Soil Health

Prospecting the cold habitats has led to the isolation of a great diversity of psychrotrophic microbes belonging to different groups. The cold-adapted microbes have potential biotechnological applications in agriculture, medicine, and industry as they can produce cold-adapted enzymes (amylase, cellulase, chitinase, laccase, lipase, pectinase, protease, xylanase, β-galactosidase, and β-glucosidase), antifreezing compounds, and antibiotics and possess diverse multifunctional plant growth-promoting attributes (production of ammonia, hydrogen cyanide, indole-3-acetic acid, and siderophores; solubilization of phosphorus, potassium, and zinc; 1-aminocyclopropane-1-carboxylate deaminase activity and biocontrol activity against plant pathogenic microbes). Cold-adapted microbes are ubiquitous in nature and have been reported from Antarctica, permanently ice-covered lakes, cloud droplets, ice cap cores from considerable depth, snow, glaciers, and those associated with plants growing in cold habitats. Cold-adapted microbial communities can be studied using culture-dependent and culture-independent techniques. Microbes recovered using both techniques revealed the occurrence of different and diverse major groups, viz., Actinobacteria, Ascomycota, Bacteroidetes, Basidiomycota, Chlamydiae, Chloroflexi, Cyanobacteria, Euryarchaeota, Firmicutes, Gemmatimonadetes, Mucoromycota, Nitrospirae, Planctomycetes, Proteobacteria, Spirochaetes, Thaumarchaeota, and Verrucomicrobia. On the review of isolated cold-adapted microbes, it was found that Proteobacteria was the most dominant phylum followed by Firmicutes and Actinobacteria. This book chapter deals with the isolation, characterization, and biodiversity of cold-tolerant microbes from Antarctica; Himalayan cold desert; glaciers; ice-capped rivers; plant-associated, subalpine region of Uttarakhand; and different sub-glacial lakes. The biotechnological applications of cold-adapted microbes have been discussed. The benificial and potential cold-adapted microbes may have applications in diverse processes in agriculture, industry, and allied sectors.

Microbiome in Crops: Diversity, Distribution, and Potential Role in Crop Improvement

Abstract The use of plant growth-promoting microbes may prove useful in developing strategies to facilitate growth of different crops. The use of microbe formulation with the aim of improving nutrient availability for plants is an important practice and necessary for agriculture. During the past couple of decades, the use of microbial inoculants for sustainable agriculture has increased tremendously in various parts of the world. Significant increases in growth and yield of important cereal crops in response to inoculation with PGP microbe have been repeatedly reported. The actual biodiversity of PGP microbes will be illustrated by examples of genera and species chosen from the literature and their mechanisms of action for the following different domain archaea, bacteria, and fungi of different phylum/groups, for example, Actinobacteria, Ascomycota, Bacteroidetes, Basidiomycota, Crenarchaeota, Euryarchaeota, Firmicutes, and Proteobacteria (α/β/γ/δ). Among these groups, Bacillus and Bacillus -derived genera (BBDG) and γ-Proteobacteria have been characterized and formulated for growth and yield of different crops. These microbes are naturally occurring that aggressively colonize plant roots and benefit plants by providing growth promotion. PGP microbes are reported to influence the growth, yield, and nutrient uptake by different mechanisms of solubilization of phosphorus (P), potassium (K), and zinc (Zn) and biological N 2 fixation and production of indoleacetic acid, gibberellic acid, siderophore, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. The diversity of microbes associated with crops and their beneficial role in crop improvement is reviewed and discussed.

Potassium-Solubilizing Microbes: Diversity, Distribution, and Role in Plant Growth Promotion

Injudicious application of chemical fertilizers in India has a considerable negative impact on economy and environmental sustainability. There is a growing need to turn back to nature or sustainable agents that promote evergreen agriculture. Potassium (K) is an important and well-known constraint to crop production. Very low rates of potash fertilizer application in agricultural production lead to rapid depletion of K in the soil. Depletion of plant-available K in soils results in a variety of negative impacts of the crops yield and soil health. Microorganisms play important role in determining plant productivity. For successful functioning of introduced microbial bioinoculants, exhaustive efforts have been made to explore soil microbial diversity of indigenous community, their distribution, and behavior in soil habitats. Soil microorganisms are directly responsible for recycling of nutrients. K is the third major essential macronutrient for plant growth. The concentrations of soluble potassium in the soil are usually very low, and more than 90% of potassium in the soil exists in the form of insoluble rocks. Use of plant growth-promoting microorganisms (PGPMs) helps in increasing yields in addition to conventional plant protection. The most important PGPMs are Azotobacter, Azospirillum, Acidithiobacillus ferrooxidans, Bacillus circulans, B. edaphicus, B. globisporus, B. mucilaginosus, B. subtilis, Burkholderia cepacia, Enterobacter hormaechei, Paenibacillus kribensis, P. mucilaginosus, and Pseudomonas putida potassium solubilizes; these are eco-friendly and environmentally safe. Therefore, the efficient K-solubilizing microbes (KSM) should be applied for solubilization of a fixed form of K to an available form of K in the soils. This available K can be easily taken up by the plant for growth and development. In this chapter has been discussed isolation, characterization, diversity, and distribution of KSM from diverse stresses such as low and high temperatures, acidity, alkalinity, salinity, drought, and plant-associated applications. These studies elaborate on indigenous K-solubilizing microbes to develop efficient microbial bioinoculant for solubilization of K in different conditions of soil which enhances the plant growth and yield of crops.