**2. Titanium dioxide nanoparticles**

Titanium dioxide (TiO2) nanoparticles (TiO2-NPs), or ultrafine TiO2, are particles of TiO2 with diameters 1–100 nm. The TiO2-NPs activity is exciting to researchers because of its specific characteristics which include; size, shape, crystal structure, surface stability among others [6]. They are among top five NPs used in consumer items such as cosmetics, food products, paints, and medicines [7]. TiO2 received USFDA approval hence regarded as safe. It is widely used as food colorant in candies, sweets, chewing gums, etc. Anatase (used in printing inks and photocatalysts), rutile (used in colorants and sunscreens), and brookite are the three primary forms of TiO2-NPs [8–12]. In 1985, Matsunaga et al. [13] first documented the antimicrobial activity of TiO2. They observed that microbial cells were dead when exposed to a TiO2-Pt catalyst illuminated with UV light.

The biocidal activity of TiO2 has been reported [14–19]. **Table 1** shows the fungicidal activity of TiO2-NPs against fungi species known to contaminate grains with the mycotoxins they synthesize.

TiO2-NPs have been widely applied as antimicrobial agents in recent years due to their unique properties such as resistance to high temperatures, low solubility, high surface area, cost-effectiveness, hydrophilicity, and strong oxidizing properties [20].

TiO2-incorporated polyethylene (PE) film inhibited growth of *E*. *coli* and *S*. *aureus*. UV light significantly enhanced the biocidal activity within 60 minutes of illumination [20]. Several studies [21–26] have documented the biocidal efficacy of TiO2 against *E. coli*, *S*. *aureus*, *P*. *aeruginosa,* and *P*. *expansum*.

The photocatalytic oxidation of surfaces coated with TiO2 and ultraviolet A (UVA) was effective against *E*. *coli*, *P*. *aeruginosa*, *S*. *aureus*, and *E*. *faecium* than the control [27]. A collaborated research [28] assessed the biocidal activity of the crude and annealed TiO2-NPs. The results revealed that doped Ag-TiO2 (7%) NPs killed 100%, 95%, and 96% of *P*. *aeruginosa*, *S*. *aureus*, and *E*. *coli,* respectively, at 40 mg/30 mL.

Assessing ecotoxicity of TiO2-NPs against bioluminescent bacterium (*Aliivibrio fischeri*), algae (*Pseudokirchneriella subcapitata*, *Scenedesmus subspicatus,* and *Chlorella vulgaris*), protozoon (*Tetrahymena pyriformis*), water flea (*Daphnia magna*), and an aquatic macrophyte, *Lemna minor* [29] revealed these organisms showed significant behavioral and physiological changes when exposed to low TiO2-NP concentrations (0.1 and 0.05 μg/L), thus demonstrated the ability of TiO2-NPs to alter molecular pathways via which these organisms obtained vital nutrition for growth and synthesis of compounds (i.e., chlorophyll, etc.).

Maneerat and Hayata [26] tested the fungicidal activity of TiO2 photocatalysts against *P*. *expansum* in the form of TiO2 powder and TiO2 coated on a plastic film. Both TiO2-NPs suppressed the conidial germination and growth of the fungi. The quantity of TiO2-NPs added correlated with the fungicidal activity.

Nitrogen-doped TiO2 [TiO2 (N)] exhibited potent biocidal activity with regards to reducing the number of surviving organisms than carbon-doped TiO2 [TiO2 (C)]. Therefore, TiO2 (N) NPs can inactivate spores of *B*. *anthracis* (hazardous

**137**

cent lamps [30].

**Table 1.**

*The Potential Application of Nanoparticles on Grains during Storage: Part 2 – An Overview…*

*Cladosporium cladospoiroides*, *Epicoccum nigrum, F*. *mucor*, *Penicillium oxalicum*, *Trichoderma* 

*Diaporthe actinidae* [25] *Erysiphe cichoracearum*, *Peronophythora litchii* [42] Molds and yeasts (not specified) [43] *Fusarium* spp*.* (*equisetii*, *oxypartan*, *anthophilum, verticillioides*, *solani*) [44, 45] *P*. *citrinum* [46, 47] *P*. *expansum* [26] *S*. *cerevisiae* [13, 48]

**Organism Reference** *C*. *albicans*, *S*. *cerevisiae* [31] *A*. *niger* AS3315 [32] *F*. *verticillioides* [33] *A*. *niger* spores [34] *A*. *niger*, *S*. *cerevisiae* [35] *F*. *oxysporum f*. sp. *lycopersici* [36] *C*. *albicans* ATCC 10231, *F*. *solani* ATCC 36031 [37] *C*. *albicans* [27] *C*. *famata* [38] *C*. *vini*, *Hansenula anomala* CCY-138-30 [39] *Cladobotryum varium*, *Trichoderma harzianum*, *Spicellum roseum* [40]

microorganism) under illumination by conventional light sources such as incandes-

TiO2-NPs are the photocatalysts used to destroy unwanted organic compounds

<sup>−</sup>) [21]. Gogniat

[41]

Photocatalysis can be defined as the catalyst-driven acceleration of a lightinduced reaction [49–52]. Homogeneous and heterogeneous photocatalytic processes utilize metal complexes (transition metal complexes like iron, copper, chromium, etc.) and semiconducting materials such as TiO2, ZnO, SnO2, and CeO2 as catalysts. In the presence of light and heat, metal complexes become excited and form metal ion complexes, in contrast, semiconducting materials become excited due to the combination of electronic structures which is characterized by a filled valence band, empty conduction band, and light absorption properties, resulting in the generation of reactive oxygen species (ROS) or hydroxyl radicals. These hydroxyl radicals inflict damage to microbial cells [49–51, 53–55]. The subsequent hole in the valence band could further react with H2O in the grains or hydroxide ions adsorbed on the surface of TiO2-NPs to generate hydroxyl radicals (OH•), with

and Dukan [56] demonstrated that DNA was denatured by hydroxyl radicals gener-

**2.1 Mechanistic action of TiO2-NPs antimicrobial activity**

electron in the conduction band reduce O2 to superoxide ions (O2

ated via the Fenton reaction resulting in cell death.

in the air, water, soil, and, more recently, in food [21].

*DOI: http://dx.doi.org/10.5772/intechopen.93213*

*asperellum*, *Pestaotiopsis maculans*

*Modified with permission from Ref 4498160008350.*

*Fungicidal activities of TiO2-NPs on mycotoxins-producing fungi*

*The Potential Application of Nanoparticles on Grains during Storage: Part 2 – An Overview… DOI: http://dx.doi.org/10.5772/intechopen.93213*


#### **Table 1.**

*Mycotoxins and Food Safety*

**2. Titanium dioxide nanoparticles**

with the mycotoxins they synthesize.

properties [20].

40 mg/30 mL.

phyll, etc.).

discussed.

promising nanoparticles (titanium dioxide nanoparticles, chitosan nanoparticles, ultradisperse humic sapropel suspension (UDHSS) nanoparticles, and carbonbased nanoparticles/nanomaterials) of interest which could be applied during grain storage. The toxicological aspects, as well as the proposed modes of application are

Titanium dioxide (TiO2) nanoparticles (TiO2-NPs), or ultrafine TiO2, are particles of TiO2 with diameters 1–100 nm. The TiO2-NPs activity is exciting to researchers because of its specific characteristics which include; size, shape, crystal structure, surface stability among others [6]. They are among top five NPs used in consumer items such as cosmetics, food products, paints, and medicines [7]. TiO2 received USFDA approval hence regarded as safe. It is widely used as food colorant in candies, sweets, chewing gums, etc. Anatase (used in printing inks and photocatalysts), rutile (used in colorants and sunscreens), and brookite are the three primary forms of TiO2-NPs [8–12]. In 1985, Matsunaga et al. [13] first documented the antimicrobial activity of TiO2. They observed that microbial cells were dead

The biocidal activity of TiO2 has been reported [14–19]. **Table 1** shows the fungicidal activity of TiO2-NPs against fungi species known to contaminate grains

TiO2-NPs have been widely applied as antimicrobial agents in recent years due to their unique properties such as resistance to high temperatures, low solubility, high surface area, cost-effectiveness, hydrophilicity, and strong oxidizing

TiO2-incorporated polyethylene (PE) film inhibited growth of *E*. *coli* and *S*. *aureus*. UV light significantly enhanced the biocidal activity within 60 minutes of illumination [20]. Several studies [21–26] have documented the biocidal efficacy

The photocatalytic oxidation of surfaces coated with TiO2 and ultraviolet A (UVA) was effective against *E*. *coli*, *P*. *aeruginosa*, *S*. *aureus*, and *E*. *faecium* than the control [27]. A collaborated research [28] assessed the biocidal activity of the crude and annealed TiO2-NPs. The results revealed that doped Ag-TiO2 (7%) NPs killed 100%, 95%, and 96% of *P*. *aeruginosa*, *S*. *aureus*, and *E*. *coli,* respectively, at

Assessing ecotoxicity of TiO2-NPs against bioluminescent bacterium (*Aliivibrio fischeri*), algae (*Pseudokirchneriella subcapitata*, *Scenedesmus subspicatus,* and *Chlorella vulgaris*), protozoon (*Tetrahymena pyriformis*), water flea (*Daphnia magna*), and an aquatic macrophyte, *Lemna minor* [29] revealed these organisms showed significant behavioral and physiological changes when exposed to low TiO2-NP concentrations (0.1 and 0.05 μg/L), thus demonstrated the ability of TiO2-NPs to alter molecular pathways via which these organisms obtained vital nutrition for growth and synthesis of compounds (i.e., chloro-

Maneerat and Hayata [26] tested the fungicidal activity of TiO2 photocatalysts against *P*. *expansum* in the form of TiO2 powder and TiO2 coated on a plastic film. Both TiO2-NPs suppressed the conidial germination and growth of the fungi. The

Nitrogen-doped TiO2 [TiO2 (N)] exhibited potent biocidal activity with regards

to reducing the number of surviving organisms than carbon-doped TiO2 [TiO2 (C)]. Therefore, TiO2 (N) NPs can inactivate spores of *B*. *anthracis* (hazardous

quantity of TiO2-NPs added correlated with the fungicidal activity.

when exposed to a TiO2-Pt catalyst illuminated with UV light.

of TiO2 against *E. coli*, *S*. *aureus*, *P*. *aeruginosa,* and *P*. *expansum*.

**136**

*Fungicidal activities of TiO2-NPs on mycotoxins-producing fungi*

microorganism) under illumination by conventional light sources such as incandescent lamps [30].
