2022 年 10 巻 p. 68-81
Climate change and industrial farming activities have negative environmental consequences on living organisms that are of considerable significance to human health and are directly or indirectly linked to agriculture. Global agricultural systems are facing numerous unexpected threats in current diversified climate change era. However advanced technologies such as nanotechnology are a helpful method to improve crop production and ensure sustainability to achieve food security. Nanotechnologies have an extensive series of application in agriculture especially in term of crop production and crop protection. Nanotechnology has potential usages in all extents of the food industry and are capable of altering their taste, and color according to the dietary requirements of the consumer. One of the most promising mechanisms through which various nanomaterials can support to decontaminate water and other heavy metals. Nanomaterials help in the conversion of radioactive materials into less toxic compounds. Similarly, environmental remediation requires various methods for the elimination of contaminants from different media in which nanotechnologies are helpful. The article concluded that substantial studies have been carried out on the usage of nanomaterials in food systems; the commercialization of nanoscale-based foods requires further analysis. Efforts to enhance consumer understanding and approval of novel nano-based food and agricultural goods are also required. The present review also discusses the role of nanotechnology in agricultural products and their food security on a sustainable basis.
Climate change is actively impacting human health, for instance through the heightened loss of life in flooding or heat stress, storms, and indirectly through changes in the supply of water, air emissions and disease vector ranges (mosquitoes), waterborne viruses, and foodborne diseases [1]. Besides, agriculture is impacted by climate change due to greenhouse gas emissions such as nitrogen oxide, methanol, and carbon dioxide. The direct sources of these emissions are use of fertilized agricultural soils in large proportion, use of tillage practices, fossil fuels and manuring of livestock [2]. Furthermore, intensive fertilizer and pesticide application and intensive plant culture significantly replenishing the soil fertility status as well as food security and releasing hazardous effects on the environment [3]. However, agricultural productivity is vulnerable to climate instability and climate change associated with temperature rises, CO2 increases, and changing rainfall trends that contribute to a major decrease in crop [4]. Therefore, it is a difficult challenge to increase the crop yield to satisfy the increasing demands due to the rising population, against the backdrop of intensive agricultural inputs and climate change challenges [5]. A variety of workers have reported recent agricultural advances covering the utilization of nanoparticles (NPs) for extra productivity and harmless usage of plant chemicals, increase the development of plants, and yield and food security [6].
In this period of climate change where global agriculture systems are fronting various unexpected challenges, but emerging innovations such as nanotechnology (NT) is a beneficial approach to increase the crop value and ensure resilience to achieve food security [7]. The NT assistance of plant protection has grown exponentially, with the ability to promote crop growth and yield by tackling the main challenge in agricultural production, of allowing plants to respond quickly to progressive causes of climate change, such as water shortages and high temperature. In agriculture, NT is used to improve food fabrication, with nutritional benefit, efficiency, and protection being equal or even higher [8]. The most effective approaches to increase crop production are the productive use of insecticides, herbicides, fertilizers, or plant progress regulators. The practice of nanomaterials, controlled release of herbicides, pesticides, and growth regulators could be accomplished and nanocapsules, for example, have recently been developed as an atrazine herbicide carrier for controlling pests and diseases [9]. Besides, NT helps to enhance agricultural productivity by increasing input quality and reduce the acceptable losses, nanomaterials with a broader specific surface area act as special agrochemical carriers, which enable site-specific regulated nutrient distribution with improved crop safety [7].
Various NPs such as aluminum (Al), zinc oxide (ZnO), and zinc (Zn), Titanium oxides (TiO2), silicon (Si), cesium oxide (CeO2), copper (Cu), and aluminum oxides (Al2O3), etc. are used to enhance the production of various crop plants [10]. These NP provide protection to plants and enhance food sustainability such as Ag has greater impacts on yield quality other than antimicrobial properties and contributes to strong nutritional value in the industry of food [10]. The NT has the potential to revive the food industry as well as agricultural productivity, and can improve the farmers and poor people’s livelihood. Previous studies suggest that Al, ZnO, Zn, and magnetite (Fe3O4) substantially increase the germination rate and the development of higher plant roots such as radish, lettuce, cucumber, grape and maize [11, 12]. The silver NPs are also helpful for the emergence of seedlings in wheat, ZnO in mungbean and sulphur (S) in tomato [11]. Furthermore, the reproductive and vegetative characteristics of fruit trees such as strawberry, coffee, date, pomegranate, mango, and grape have been greatly improved by macro and micro-scale nano fertilizers such as Zn, B, Mn, and Mg [12].
1. 1 Nanotechnology in agriculture and other fieldsNanotechnology can change several areas of agriculture and the food business by applying current techniques for disease diagnosis and treatment, enhanced plant nutrient uptake capacity, and so on. Herbicides and insecticides will be more effective with lower dosages owing to nano-based crystals, which are currently being developed. Agriculture’s ability to combat infections and viruses will be enhanced by smart delivery systems and sensors [2]. The NT is used in the food sector in a variety of ways, including farming, food processing, and food packaging.
1. 2 Potential of nanotechnology for crop productionSeed germination is a crucial stage in the life cycle of a plant, as it aids in development of seedling, survival of seeds, and population dynamics. Seed germination, on the other hand, is heavily influenced by a variety of factors, includes environmental factors, genetic traits, moisture content, and fertilizer application [13]. In this regard, several previous studies have demonstrated that nanomaterials improve plant seedling as well as the growth and development of plant [14]. Similarly, seed germination in crop plants is aided by nano SiO2, TiO2, Zeolite and ZnO applications [15]. Disfani et al. [16] also originate that Fe/SiO2 NPs offer a lot of potential for improving barley and maize seed germination. Despite a huge research on nanomaterials’ favorable effects on germination, the processes by which nanomaterials can increase incubation are quiet unknown. Nanomaterials have been shown in a few studies to have the ability to infiltrate the seed coat and promote water absorption and utilization, which activates the enzymatic system and resultantly improve the germination rate during the year 2002 [17].
Nanomaterials such as hydroxyl fullerenes and Zn, Fe and Cu-oxides, in addition to germination, have been shown to improve crop growth and development as well as quality in a variety of crop species [18]. Gao et al. [19] found that stimulated cell divisions in arabidopsis hypocotyls, which increased hypocotyl growth. Seed dressings containing fullerol have also been reported to boost the concentration of bioactive substances such cucurbitacin-B, lycopene, charantin, and inulin in bitter melon fruits, increasing fruit number, size, and yield by up to 128% [20]. Ghafari and Razmjoo [21] demonstrated that the use of nano Fe fertiliser improved not only the agronomic properties of wheat with higher sowing density, but also the essential oil content of the plants. By enhancing agronomic and physiological features, foliar application of nano-Zn and Si fertilizers enhanced green production (12.6%), reduced pollution and fertiliser costs, and enriched rice grains with Si and Zn, resulting in greater yield and nutrient accumulation in grains [22]. These results demonstrated NP’s potential for increasing yields of crops and creation worth. Though the precise mechanism that occurs following plant advancement and eminence is unknown, it might be explained in part by nanomaterials’ capacity to fascinate additional water and nutrients, which serves to promote root system vitality through increased enzyme activity. In addition, studies of nutrients on slow/controlled release or control loss of nano fertilizers in water and soil have revealed that the long-term availability of all doped nutrients to the plant throughout the entire crop cycle is critical for promoting flower number, plant growth, and fruit production [7]. For instance, urea fertiliser coated with hydroxyapatite nanomaterials releases N very slowly and uniformly (according to the requirement of the plants) over up to 60 days, whereas typical bulk fertiliser loses N quickly and unevenly within 30 days, reducing plant nutrient efficiency and negatively affecting crop development [20].
In contrast, numerous studies have shown inconsistent data about the better effects of nanomaterials on seed germination (seedlings of different crops) and crop growth. Variability in nanomaterial attributes, such as size, surface coating, shape, and electrical properties, as well as dose, application method, and plant species analyzed, may all contribute to this. For instance, Disfani et al. [16] also found that applying 15 mg kg-1 of nano Fe/SiO2 to barley and maize seedlings increased maize plant shoot length by 8.3% and 20.9%, respectively; however, when the concentration was increased to 25 mg kg-1, the maize and barley shoot length was reduced markedly, implying that crop growth is dependent on the applied nanomaterial concentration. Zheng et al. [23] found that the application of TiO2 @ 2.5% cause improved photosynthesis in spinach. However, the higher concentration of TiO2 (i.e. 4%) cause reduced physiological contents. Elfeky et al. [24] indicated that the mode of nanomaterial application affects plant development performance. When compared to soil application, they discovered that total carbohydrate, fresh weight, Fe content, total chlorophyll, branches/plant, leaves/plant, plant height, dry weight and essential oil levels of Ocimum Basilicum plants all rose significantly after foliar application of nano Fe3O4.
1. 3 Potential of nanotechnology for crop protectionDifferent factors such as rats and diseases have a substantial impact on crop productivity. Farmers have trusted significantly on pesticides to decrease crop losses, which has a harmful impact on human health and environmental sustainability. The zone of inhibition for Xanthomonas axonopodis pv. malvacearum and Xanthomonas campestris pv. campestris, two major bacterial pathogens of Malvaceae and Brassicaceae family crops, respectively, shows that biosynthesized Ag NPs obtained using stem extract of cotton plant (Gossypium hirsutum) have a strong antibacterial activity [25]. The careful application of nanomaterials can boost crop output while preserving the environment’s health. Because of their high efficacy and eco-friendliness, research on the use of nanocomposites in plant protection has exploded in recent years. When fungicides antracol are mixed into chitosan nanocomposites (Ag@CS), the antifungal activity is higher than when each component is used alone [26]. The creation of Bacillus thuringiensis (Bt) nanocomposites comprising active Bt has boosted the effectiveness and shelf life of insecticides while also lowering the dosage required previously. However, the processes behind Bt-based nanocomposites’ activities are still unknown [27]. A variety of metallic NP i.e. copper and silver efficiently controls antimicrobial activities. Polymer-based copper nano-compounds have antifungal action against Candida albicans plant-infecting fungus has been explored [28]. Park et al. [29] investigated the efficacy of silica-silver NP in controlling plant-infecting fungus Magnaporthe grisea, Rhizoctonia solani and Botrytis cinerea. Powdery mildew, a pumpkin disease, was also controlled using nano-based products, and it was found that the infecting bacteria on the leaves that caused the illness vanished three days after spraying the product. Nanotechnology’s contribution to plant protection products has skyrocketed, allowing for improved agricultural yields. In general, conventional crop protection measures entail the use of fungicides, herbicides, and insecticides in vast quantities and at high doses. More than 90% of pesticides used are either missing in the environment or incapable to influence the critical target locations for efficient pest control. This not only raises food production costs, but it also depletes environmental systems. It should be mentioned that the occurrence of active elements in a formulation’s lowest effective concentration at the target areas is critical for ensuring improved plant protection against pest attack and eventual crop loss [9]. In this regard, developing new plant protection formulations has long been a challenging area of agricultural research. Nanoformulation or encapsulation of pesticides is one such technique that has changed the plant protection industry. Although other developed nano-structures have pesticidal characteristics, pesticide nanoformulations include a very tiny number of particles that function as active components. Without losing effectiveness, nanoformulations or encapsulations of pesticides allow for the persistence or controlled release of active components in root zones or inside plants. Traditional pesticide or herbicide formulations, on the other hand, not only reduce chemical solubility in water, but also harm other species, increasing the sensitivity of the target organism. Nanoformulations, on the other hand, help to overcome the constraints described above. Petosa et al. [30], for example, found that pesticide nanoformulations improve pesticide effectiveness by modifying pesticide transport potential, resulting in higher crop yields. This might be attributed to nanoformulations’ improved dispersion and wettability, which minimize organic solvent runoff and pesticide movement. Increased stiffness, solubility, thermal stability, biodegradability, permeability, and crystallinity are all attributes of nanomaterials in pesticide formulations, which are all important for a robust agricultural production system.
1.4 Potential of nano fertilizers for crop nutritionIn general, critical nutrient supplementation that may be artificial or natural (element fertilization) is required to improve soil fertility and crop productivity. Nonetheless, one of the most crucial criteria for long-term agricultural development is proper fertilizer control. The right to food is a basic human right. Food security is jeopardized in part due to a scarcity of natural resources. The present world population (seven billion) is expected to grow over time, reaching roughly nine billion by 2050. About 60–100% more food will be required to feed the growing population [31]. Intensive farming is being performed to fulfil the rising food demand, which finally leads to a vicious cycle of soil fertility exhaustion and agricultural production loss. According to estimates, nearly 40% of the world’s agricultural land has been severely degraded, resulting in a significant loss of soil fertility as a result of such intensive farming techniques [32]. For decades, the nutrient usage efficiency of traditional fertilisers, such as 30–35% N, 18–20% P, and 35–40% potassium (K), has remained stable [33], The continual use of excessive fertilisers has a negative impact on the soil’s natural nutrient balance. Aside from that, aquatic habitats have been severely damaged as a result of harmful materials leaching into rivers and water reservoirs, contaminating drinking water as well.
Engineered NP in sustainable agriculture have revealed an entirely new method to food production that may overcome agricultural sector unpredictability while using minimum resources. Green nanotechnology’s revolution has changed the global agriculture scene dramatically, and nanomaterials like nano fertilizers have showed promise in fulfilling global food demand forecasts and assuring sustainable agriculture. Nano fertilizers may be the greatest option for alleviating macro- and micronutrient deficiencies through improved nutrient usage efficiency and overcoming the persistent problem of eutrophication. For example, conventional nitrogen fertilisers suffer massive losses from the soil due to leaching, evaporation, or even degradation of up to 50–70%, lowering fertiliser efficiency and raising production costs. The encapsulation of nutrients with nanomaterials is the most common method of producing nano fertilizers.
According to Abdel-Aziz et al. [34], chitosan-NPK fertiliser significantly increases the harvest index and mobilization index of the calculated wheat yield variables when compared to control yield factors. Nanomaterials stimulate a range of critical features of plant biology because plant leaf and root surfaces are the major nutritional gateways for plants and are particularly porous at the nanoscale [35]. Nano fertilizers can increase plant nutrient absorption through these holes by exploiting endocytosis or ion channels, or the approach can enhance complexation with molecular transporters or root exudates by forming new pores.
1.5 Mechanism of improving plant growth and phenologyMaintenance the soil system means proper pH, considerable amount of organic matter, and other processes are necessary but its very difficult to adjust [36]. Therefore, the NP of foliar and soil application activates different enzymes, for instance, TiO2 improves the nitrogen assimilation by improving the activity of enzyme nitrate reductase [37]. Furthermore, the chloroplast of photosynthetic species, including plant and algae, the preferential absorption of TiO2 has been well demonstrated [38]. The chloroplasts are the key places for reactive oxygen species (ROS) creation in crop plants and TiO2-induced shift in ROS levels may be connected with modification in chloroplast operations [39]. It also improves nitrogen assimilation by improving the activity of enzyme nitrate reductase [37]. At the macro level, nanomaterials improve soil strength by strengthening the soil skeleton and changing the pore NP, while at the micro level, NP have distinct characteristics from bulk materials, such as height, structure, surface functional groups, bond strength, and processes, all of which influence the bulk material’s engineering properties and efficiency [40]. Similarly, the NPs of the Cu, ZnO, TiO2 and Ag do not affect the microbial population in soil [41]. The NP of CeO2 is helpful in increasing the level of nitrogen in soil through nitrogen fixing bacteria and reduces the nitrogen fixation rate [42].
However, all the NPs are being used to improve soil health on a sustainable basis and improve growth as shown in Figure 1.
Figure 1: Effect of nanotechnology on plant growth and phenology
Nanotechnology holds tremendous potential to deliver modern and expanded environmental clean-up remediation technologies [43]. There are three types of nano-based materials such as polymers based, carbon-based, and inorganic based [44]. Nanomaterials efficiently remove biological contaminants and pollutants from different environmental components. They act as adsorbents, catalysts and complexes. These nanomaterial forms are used for the elimination of CO, SO2, Mg, As, Fe, MgO, NO3, TiO2, WO2 and heavy metals [45]. The NT have three main functions that include (a) sensing, (b) detection and (c) removal [45] of organic pollutants like aromatic hydrocarbon, aliphatic hydrocarbons, and biological substances such as pathogens, antibiotics, parasites, and bacteria [46]. Furthermore, the nanomaterials also include nanosensors and nanofiltration [47]. Due to the high surface area and associated high reactivity, it performs better and more efficiently. The nano size materials of NT display better efficiency in environmental remediation and other traditional techniques that make it possible to facilitate in-vitro remediation rather than ex-vitro remediation [48]. The mechanism of NT in environmental remediation is given as in Figure 2.
Figure 2: Effect of nanotechnology on environmental remediation
Similarly, NT enhances the texture and taste of ingredients and can minimize the fat contents or encapsulate nutrients (vitamins) to assurance that they do not deteriorate over the shelf life of a product [49]. At the molecular scale, the mechanism of host and parasite interactions, the production of next-generation insecticides and healthy carriers, NT theoretically boost our currently dismal nutrient usage effectiveness through nutritional quality barriers [50]. The nano-formulation of fertilizers and breaking yield by bio NT exploration, and control of diseases and pests [50] to enhance the food quality. Mostly, (a) polymeric nanoparticle, (b) liposome, (c) hydrogel nanoparticle, (d) micelle, (e) carbon nanotube and (f) dendrimer [51] are used to preserve food and for various other purposes such as agricultural production.
2.1 Nanotechnology in food protectionThe pathogens can be selectively bound by several NP, which are eliminated in various processes [52]. Nanosensors are particularly susceptible to food spoilage, which can show indirect changes in the color of food or gases emitted when food is spoiled. The NP of gold could be used to detect aflatoxin B1, which is also present in milk [53]. Furthermore, nanosensors are used to show the pesticide presence in vegetables and fruit surfaces and the carcinogens can also be detected in food products by certain nanosensors [54]. Nanosensors are used effectively in the field of food microbiology to alert customers and producers to the safety status of foods since they can reliably show the existence of any pathogens in food products [54]. The NT is starting to be used by the food industry to produce nanoscale ingredients to enhance food color, texture, and flavor [55] as food additives, the NP TiO2 and SiO2 [56] and amorphous silica [57] are used. Besides, TiO2 is also used in the powdered sugar coating on doughnuts as decoration.
2.2 Nanotechnology in food processingThe NPs are being used in food processing industry to improve food purity and to maintain the food colour. The nano-structured food’s additives are manufactured with statement that they have increased flavor, texture, and consistency [58] and enhance the life-span of various types of food ingredients and also help to reduce the amount of food waste because of bacterial infestation. Nano-encapsulations block odors or, monitor the relations of dynamic constituents with the food matrix, trace the discharge of dynamic agents, ensure that they are accessible at the required target time and pace [59]. They protect them during preparation, storage, and use from moisture, humidity, chemical or biological degradation, as well as compatibility with other compounds [59].
By supplying bioactive compounds to enhance bioavailability in foods, nano-encapsulation systems have the potential to increase food handling. Mostly, (a) Polymeric nanoparticle (b) liposome (c) hydrogel nanoparticle (d) micelle (e) carbon nanotube and (f) dendrimer [51] that are used for agricultural production as well as pollutant remediation’s.
2.3 Nanotechnology in food packagingThe core group of current food industry applications consists of NT-derived food packaging materials that grow food contact materials [60]. Currently, the integrated nanomaterials are used to enhance the packaging characteristics, such as longevity, temperature resistance, gas barrier properties, temperature tolerance, NP that are antimicrobial or oxygen-scavenging, detecting, and rebounding nanosensors [61]. Without major improvements in density, clarity, and processing characteristics, a comparatively low NP level is necessary to alter the properties of packaging materials [62]. Among the first nanocomposites to come on the market, polymer composites containing clay NP reduce gas permeation and offer significant improvements in gas barrier properties [62]. To destroy foodborne pathogens such as Listeria, Salmonella, and Escherichia coli on steel food processing surfaces, engineered water nanostructures created as aerosols are very operative [63]. These nanomaterial-containing food contact compounds can move from food packaging to food, but this technique also needs to show regulatory compliance before achieving widespread market adaptation. The mechanism of food packaging is shown in Figure 3.
Figure 3: Role of nanotechnology in food packaging
In packaging containers, silicate NP may restrict the movement of oxygen, limit moisture leakage, and ensure that food stays garden-fresh for a longer time [64]. Nanocomposites help to keep food ingredients fresh for a longer time, regardless of the food product’s bacterial infestation. By functioning as gas barriers, they reduce the leakage of carbon dioxide from carbonated drink bottles [64]. Nano-sensors help to detect any slight variations in food color as well as any gases that are created as a result of spoilage. Furthermore, nano-sensors are highly sensitive and selective to these shifts, which makes them powerful than traditional sensor approaches [65]. The gas sensors are made of platinum, palladium, and gold [66]. In certain cases, the sensitivity of sensors is improved greatly by single-walled carbon nano-tubes that are made up of DNA, and nano-sensors can also be used in agriculture, where pesticides can be tested on vegetable and fruit surfaces [67, 68]. To detect carcinogens in food products, nano-sensors have also been used. To discourage the degradation of its features, food treatment and preparation is mentioned as food preservation. Many of the traditional methods of storing food are frozen, dried, and canned. The NT, however, has come up with improved and additional effective ways to help to conserve food, such as the use of nano-sensors [69] as prescribed in Figure 4 and 5.
Figure 4: Effect of nanotechnology in food preservation
Figure 5: Role of nanotechnology in food preservation
Nanocarriers are also being used in agricultural goods as transport mechanisms to bear food additives deprived of influencing their simple morphological characteristics. The extent of particles can directly influence the distribution of any biologically active substance to different locations inside the body [70]. It has been observed that only submicron NP can be effectively ingested in certain cell lines, but not the larger micro-particles [70, 71]. Bio-based bioactive compound delivery systems have a broad range of morphology that disturbs their firmness and efficient performance. The incorporation of bioactive compounds into food products offers additional health benefits beyond simple nutrients by using micro-and nano-delivery mechanisms before their encapsulation can protect against unnecessary environmental conditions [71].
The benefits of nanotechnology in the food industry are projected to develop because of its wider application in almost all agricultural-related fields from manufacturing to distribution, packaging, shipping, shelf life, and bioavailability, this modern, quickly evolving technology influences every part of the food system. Because of their special and novel properties, commercial applications of nanomaterials in the food industry will expand. There will need to be increased human sensitivity to nanomaterials. The health effects of nanomaterials in food are also of key public interest. The ability to measure nanomaterials during the food life cycle is essential to the consumer product’s supply quality, protection, and future benefits.
High manufacturing costs, difficulties with the scalability of R and D for prototype, industrial development, and questions regarding public awareness of the environment, health and safety issues are the common challenges associated with the commercialization of NT. Governments around the world should, prior to selling and wholesale use of these nanomaterials, develop general and stringent standards and surveillance.
The author is highly thankful to the Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Punjab, Pakistan for their moral support.
