Sustainable Utilization of Fungi in Agriculture and Industry

Fungi play a major role in the well-being of human life as they are involved in health and nutrition processes on a large scale and are a major component of the global economy. Furthermore, they are the natural nutrient recyclers in the environment and thus balance the ecosystem. Also, through mycorhizal relationships, the fungi help in enhancing soil fertility by increasing the surface area for absorption of nutrients such as phosphorous, nitrogen, sulfur, etc., and other minerals such as zinc and copper. As fungi interact with various plant pathogens affecting crop production, they can be used as Microbial biological control agents or biopesticides and can be replaced for the usage of hazardous chemical pesticides for controlling plant pathogens. Here, we tried to explain the fungal importance to mankind and the ecosystem by listing its various applications in human life. 

Soil health or soil quality is governed by a continuous, functional interplay between the soil and its microbiota, plants and animals. Soil quality is crucial for sustainable agriculture production and for nurturing the health of all living organisms. It is therefore in the best interest of society to prioritize sustainable soil management practices for future generations. Microbes play a vital role in maintaining ecosystems by coordinating with plants to facilitate nutrient and organic matter cycling. A consortium of fungi plays a critical role in degrading and transforming dead organic matter into suitable forms that can be reused by other organisms. As ecosystem regulators, fungi enhance the structure of soil formation and regulate physiological processes within the soil, making it a supportive habitat for other living organisms. They also help in controlling plant diseases and pest infestations by acting as biocontrol agents. Understanding the roles of fungi and soil enzymes in the earth’s biogeochemical cycles can facilitate improved agricultural productivity and sustainability. For example, increasing the diversity of beneficial fungi in a habitat improves soil fertility, supporting sustainable production of plant based products while mitigating the application of undesirable chemicals as pest control agents. 

Fungi are an important component of microbial ecology. These are a community of eukaryotic species and food sources, organic acids, alcohol, antibiotics, growth-enhancing compounds, enzymes, and amino acids. Fungi contain many microorganisms under the expanse, which include molds, yeasts, and mushrooms. The function of fungi primarily includes the biodegradation of organic waste material and the action on cellulose, lignins, gums, and other organic compounds. Fungi are present everywhere, i.e., they are cosmopolitan, surviving the wide range of pH and temperature. Fungi play a key role in numerous biological cycles, including mineral and water absorption, chemical transition, stomatal activity, and biosynthesis of substances, including biostimulants, auxins, lignan, and ethylene, increasing the functionality of plant species to identify and cope with adaptive challenges, such as drought, salinity, humidity, cold and significant metals. The interaction of fungi with plants can be represented by three terms, namely, mutualism (mycorrhizal association), pathogenicity (parasitic fungi), and nutrient cycling (saprophytic fungi). The application of cultivating fungi as a soil quality booster has been highlighted as it produces various extracellular enzymes, which are integral components of nutrient cycling within natural and disturbed ecosystems.

There are many non-saprophytic fungi that are involved in symbiotic relationships with higher plants, which include both mutualism and parasitism. The most common mutualistic relationship involving fungi belonging to Ascomycota, Basidiomycota, or Zygomycota, and roots of 90% of all vascular land plants is termed mycorrhiza. In this association, the fungus grows on ectomycorrhiza or in endomycorrhiza, the roots of most terrestrial plants. The mycorrhizal fungus benefits from the carbohydrates that the host plant provides, whereas the latter is benefitted from the extensive fungal mycelia that have a greater surface area and penetrate not only deep down but also go distantly within the soil to procure water and water-soluble essential nutrients, especially nitrogen and phosphorus, for the host. Also, the mycorrhizal fungi offer increased protection to their host plants against some phytopathogens. As mycorrhizal associations are found in early fossil records, it is believed that they allowed the early terrestrial plants to colonize and survive. Another fungus–plant mutualism involves the endophytic fungi that usually dwell inside the tissues of the host plant, release toxins to repel the herbivores, and also impart resistance to the plant against environmental stresses. On the other hand, fungi parasitic on host plants live in or on them, use specialised structures called haustoria to procure nutrients from them, and produce necrosis-promoting enzymes. This may lead to some of the most devastating diseases in the crop plants, eventually killing them and severely affecting the country’s economy

Soil fungi constitute a key component of agroecosystems because they provide green services that influence food and bio-product production. Entophytic fungi play a major role in growth promotion and relieve biotic and abiotic stresses in plants. Phyto-hormones, antimicrobial agents, agrochemical bioactive metabolites produced by fungal endophytes enhance sustainable agriculture. Because of soaring cost and pollution-related issues, interest has shifted towards various methods like the use of biofertilizers and bioinsecticides to control pests. Biofertilizers and bioinsecticides are safe and cost-effective alternatives to chemical pesticides and are considered high potential fertilizers because of their wide range of plant growthpromoting activities. The present chapter describes the role of endophytic fungi in the agriculture sector.

Soil is one of the main habitats of fungi and bacteria, and their interactions with the host plant help and promote plant growth and productivity in agriculture. Agronomists and environmentalists are focussing on sustainably managing the agroecosystem by using plant growth-promoting microbes (PGPM). They include bacteria called plant growth-promoting rhizobacteria (PGPR) and fungi referred to as plant growth-promoting fungi (PGPF). Plant growth-promoting fungi (PGPF) are nonpathogenic soil-borne fungi that establish a positive interaction with plants in the rhizosphere. PGPF can improve crop productivity by improving seed germination vigour root and shoot morphogenesis, and flowering through direct or indirect mechanisms, which include solubilizing nutrients, regulating hormones, producing enzymes, organic compounds, resistance to abiotic stress, and suppressing phytopathogens. The utilization of PGPF can be considered an eco-friendly method of improving crop production. The potential effective microbes may also be added in the form of biopesticides and biofertilizers promoting the growth of plants. The use of new biotechnological tools to aid genetic engineering of the PGPF has resulted in genetic transformation and overexpression of synergistic action of one or more traits, which could enhance plant growth, confer improved crop benefits, and produce sustainable yield. The chapter describes the diversity of PGPF found in the soil and their role in promoting plant growth and yield. The chapter also discusses the various mechanisms of PGPF interactions with plants and their beneficial roles in promoting crop productivity leading to sustainable agriculture. 

 Several studies on bioinoculants have been conducted in order to address the most serious threat to our nation's security, namely food security. This problem can be solved by re-evaluating our practises and skills in order to increase food production through the use of sustainable farming methods. Several microorganisms can be found in rhizospheric soils in nature. These organisms solubilize nutrients and facilitate nutrient uptake by plant roots, promoting plant growth through natural processes such as nutrient cycling and absorption, stress tolerance, immunity induction, and so on. Microbes include mycorrhizae, cyanobacteria, bacteria, actinomycetes, and others. Plant growth-promoting microorganisms rely heavily on mycorrhizae (PGPM). So far, seven different types of mycorrhizae have been identified. The arbuscular and ectomycorrhizal fungi are the most numerous and widespread mycorrhizae. Arbuscular mycorrhizae (AM) fungi are important in improving soil physicochemical properties and interacting with other PGPM such as phosphate solubilizing bacteria, nitrogen fixers, and so on. Chemical fertilisers used in agricultural fields reduce AM and its potency. Because these organisms cannot be cultured, PCR techniques can be used to obtain sufficient amounts of DNA from them. The focus of this chapter has been on arbuscular mycorrhizae (AM) fungi. An attempt was made to study AM fungi colonisation using PCR in order to better understand its efficiency. Such research contributes to the goal of transforming food insecurity into food security. 

Mushrooms are protein-rich, highly nutritive, popular food around the world. The cultivation of mushrooms has been in practice for decades. Studies have been conducted to utilize the agricultural waste, and agro-forest remains as the substrate for mushroom production. Agri wastes such as wheat straw, paddy straw, bran, coffee grounds, banana leaves, sawdust, etc., are highly used, and the availability of such substrates is not common among the cultivating areas. Besides the development of new protocols and the invention of a perfect combination of the substrate and supplements is an ongoing interest in the mushroom production industry. In Karnataka, agricultural remains such as areca husk, sugar cane bagasse, paddy straw, and maize stem are available to use for mushroom cultivation. Also, agro-forest residues like Cassia tora are a substantial material to turn waste into the substrate. This chapter is an approach towards such substrate utilization to improve the economy of the farmer community and a promotion towards sustainable mushroom production. 

The use of chemical fertilizers improves plant growth growth and causes pollution, affecting human health. The use of microorganisms to increase the plant yield has many advantages viz., eco-friendly, economical, and easy. The fungi produce many secondary metabolites and can be used to promote plant growth. This will be a sustainable approach and also avoid pollution. The fungi produce plant growth promoting substances, act as strong biocontrol agents, and also show antimicrobial effects against the harmful pathogens, thus preventing the diseases of the plants. This chapter focuses on the importance of fungi in agriculture, which will help farmers. The solid-state fermentation using Aspergillus sp. for plant growth-promoting substances is also mentioned in the chapter. The chapter is significant as it highlights the use of the biological process to improve plant growth, which is the need of the hour. 

Fungi are the second largest group of eukaryotes and play a vital role in the biological system. These fungi are cell factories that produce a variety of industrially important secondary metabolites (SM) that are beneficial for humans, animals, and the environment. Microorganisms are a rich source of natural compounds with a significant commercial value; on the other hand, they produce low-quality products that may not satisfy industrial standards for commercialization. Numerous fungal species produce key industrial enzymes, antibiotics, anticancer drugs, cholesterol-lowering drugs, and immunosuppressants. Antibiotics belonging to the β lactam family are the most often prescribed antibiotics worldwide. Penicillin has a core structure, 6-amino penicillanic acid (6-APA), interwoven with the ß-lactam ring and drives the development of semisynthetic antibiotics. Several dermatophytoses are treated with griseofulvin (GRI), and mycophenolic acid (MPA), and the cholesterol-lowering drugs (lovastatin and compactin) are produced from Aspergillus and Penicillium species, respectively. The SM is also effective against most of the pandemic novel coronavirus (SARS-CoV2), human immuno virus (HIV), and influenza virus (H1N1) strains protease inhibitors that limit virus propagation. Furthermore, natural antioxidants (amanitin, ferulic acid, resveratrol, and flavonoids) are synthetically conjugated or co-crystallized with active SM for clinical uses. Many biosynthetic gene clusters, comparative genomics, and functional transcripts are encoded in fungal genomes, reigniting interest in discovering new compounds. The strong transcriptional regulation likely clarifies the metabolic routes in the genome. Viable approaches necessitate the availability of genome sequences, molecular tools, and a strategy tailored to alter the genomes of specific strains for industrially significant molecules. Researchers have devised a new strategy for strain generation of various genetic engineering tools, involving recombinant DNA technology, protein engineering, metabolite flux pathways, and synthetic biology approaches, using a basic understanding of genetic makeup.

Chitinases are cosmopolitan lytic enzymes secreted by microbiomes that fall under the domain of fungi, yeasts, bacteria and plants. Most fungal plant pathogens, human infectious agents and post-harvest damage caused by pathogens have been a serious threat to the economy and human health. Like fungi, crabs, insects, lobsters, shrimps, and invertebrates all have a hard disintegrating, flexible polymer called chitin that forms the exterior skeleton. It poses a wide-range of environmental problem and a major threat to humans, plants and animals. According to functional genomic research, there is a large diversity of chitinases-producing fungi in nature. They have adapted to a wide range of habitats on Earth including plants, animals and manmade natural and artificial habitats. Chitinases, both native and genetically modified, have been produced and expressed in an expression system such as Escherichia coli or Pichia pastoris through recombinant DNA technology. This versatile recombinant chitinases can be used for long-term growth and productivity. As a whole, chitinases have a wide range of applications in agriculture, horticulture , plant health, and bio-control of pests, and even some fuel processing, genetically engineered molecule-based therapies, polysaccharide hydrolysis, biomedicine, pathogenic/virulence agents, antifungal agents, and as a drug delivery system.