**3. Chitosan nanoparticles**

Chitin and chitosan have been widely used in the fabrication of polymer scaffolds [73]. Chitosan is a linear polysaccharide, a nontoxic biopolymer derived from the deacetylation of chitin, and used in many fields, including agriculture, medicine, and in vinification due to its biocidal potential. In agriculture, chitosan is used as biopesticide; in medicine, it is used to stop bleeding, wound healing, and as an antibacterial agent. Biodegradability, high permeability, nontoxic to humans, and cost-effectiveness are the features which make chitosan NPs unique. Chitosan and its derivatives have attracted considerable attention due to their biocidal activities [74, 75]. Several authors have reported the beneficial application of chitosan and its oligosaccharides which includes antitumor [76], neuroprotective [77], antimicrobial [78–85], and anti-inflammatory [86] agents. **Table 2** summarizes the fungicidal activities of chitosan against important agricultural microorganisms contaminating stored grains.

Fungal decay on pear fruit was suppressed by the combination of chitosan, yeast antagonist *Cryptococcus laurentii*, and CaCl2. The results showed that mixture of chitosan at 0.5% and *C*. *laurentii* exerted greater effects compared to chitosan or *C*. *laurentii* alone. CaCl2 showed little antifungicidal activity; however, it combination with chitosan and *C*. *laurentii* led to an effective and stable reduction of fungal decay [87], thus minimize or eradicate the menace of postharvest losses. Anthracnose in papaya caused by *Colletotrichum gloeosporioides* was controlled by the combination of *Burkholderia cepacia*, chitosan (0.75%) and CaCl2 [88]. Postharvest blue, green, and grey molds affecting apple, oranges, and lemons were effectively controlled by mixing glycol chitosan (0.2%) with *Candida saitoana* [89–91]. Ag/ chitosan-NPs showed significant antifungal activity against *A*. *flavus*, *A*. *alternata*, and *R*. *solani* hence could be used during grain storage [92, 93]. The synergistic effect (fungicidal activities) of hybrid copper(II) chitosan NPs to inhibit the growth of *F*. *graminearum*, *Verticillium dahlia* 57, and *F*. *solani* 169 was reported. In both cases, the NPs exerted an excellent efficacy in repressing the growth of fungi [94, 95]. Other authors reported that certain strains of *A*. f*lavus*, *Cladosporium cladosporioides*, *P*. *aurantiogriseum*, and *Torulaspora delbrueckii* were resistant to chitosan at levels as high as 1% [7, 96]. The application of chitosan (0.025 and 0.05%) was effective against *Saccharomycodes ludwigii* and *Saccharomyces exiguous*. A rapid reduction in the number of yeast colonies was observed 2–4 min after application [97].

According to an earlier report, the effectiveness of the biocidal activity of chitosan depends on the molecular weight, degree of acetylation, and concentration [98, 99]. The application of NPs coated with polyethylene glycol (PEG) and natural garlic oil against *Tribolium castaneum*, a vital storage pest showed high efficiency over an extended period (8 months) due to the slow and persistent release of the active components [100]. The study highlighted the potential application of PEG-NPs as capsules to encapsulate various natural bioactive ingredients (i.e., oil from *Azadirachta indica*, extracts of *Khaya anthotheca*, alkaloid extracts of *Piper guineense* [101], etc.) for controll release and subsequent killing of microorganisms and pests during grain storage. Furthermore, [102, 103] extensively reviewed the literature on the biocidal activities of natural compounds (i.e., herbs, species, etc.) and its potential application in postharvest control.

#### **3.1 Mechanistic action of chitosan nanoparticle antimicrobial activity**

According to literature [116, 117], chitosan is composed of polycationic copolymers, with glucosamine and N-acetylglucosamine as axillary units, which contributes to its antimicrobial activity. The difference in environmental pH, pKa

**141**

**Reference**

[104] [105] [106]

Not reported

85, 81, and

82 for low-,

medium-, and

high-molecular

weight chitosan

respectively

79 Not reported

*S*. *exiguus*, *S*. *ludwigii*, *T*. *delbrueckii*

*C*. *neoformans* strain *B3501*

0.05%, 0.005% Different concentration (0, 0.625,

1.25, 2.5, and 5 mg/mL) was

employed

Not reported Various concentrations were

Coating

applied for in vivo (0, 0.1, 0.5 and

1.0% (w/v)) in vitro (0, 0.001,

0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,

0.7, 0.8, 0.9, and 1.0% (w/v))

experiment

0.1, 0.5, or 1.0 mg/mL for the

Solutions

fungicidal test while 0.9 mL of

LMW or DDC-LMW chitosan was

used for the bacteriostatic test

Coating

[97] [107] [108]

[87] [109]

Crab shell

82 Y-2594,

*F. oxysporum f*. sp. *radicis-lycopersici* **1**27, *Candida krusei* VKPM

*E*. *coli* ATCC 5945, *P*. *aureofaciens*VKPMB-7542, *E.* 

*agglomerans* VKPM B-7541, *B*. *subtilis* VKPM B-7540

Industrially prepared

95

Psychrophilic, mesophilic, *Pseudomonad*, yeasts and molds

*P*. *expansum* (blue mold)

chitosan

Crab shell

~90

Not reported Not reported

Not reported (industrially made)

Not reported

75–85

*A*. *flavus* IMI242687,

*C*. *cladosporioides* IMI 274019, *M. racemosus* 

*IMI 017313, P*. *aurantiogriseum* IMI 297953, *Byssochlamys* spp.

BF, *Byssochlamys* spp. GCB, *Byssochlamys* spp. SB, *S*. *cerevisiae* 28,

*S*. *cerevisiae* 3085*, S*. *cerevisiae* SD,

*Z*. *bailii*906,

*exiguus* 391, *S*. *pombe, S*. *ludwigii*

*A*. *alternata*, *B*. *fabae*, *F*. *oxysporum*, *P*. *digitatum, P*. *debrianum*,

250, 500, 1000, 1500, 2000, 2500,

Solutions

3000, 3500 and 4000 mg/L

*R*. *solani*

*Z*. *bailii* HP, *S.* 

(industrially made)

**Sources of chitosan (CTS)**

**Deacetylation (%)**

71.5

**Microorganisms**

*A*. *niger*, *A*. *parasiticus*

**Concentration** 0 (control), 0.1, 0.5, 1.0, 2.0, 3.0,

Solutions

4.0, and 5.0 mg/mL

0, 1, 5, 10 g/L (fungi) and 5 mL

Solutions

(for yeast)

**Form applied**

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

Solutions

Biofilm

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


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

*Mycotoxins and Food Safety*

stored grains.

**3. Chitosan nanoparticles**

Chitin and chitosan have been widely used in the fabrication of polymer scaffolds [73]. Chitosan is a linear polysaccharide, a nontoxic biopolymer derived from the deacetylation of chitin, and used in many fields, including agriculture, medicine, and in vinification due to its biocidal potential. In agriculture, chitosan is used as biopesticide; in medicine, it is used to stop bleeding, wound healing, and as an antibacterial agent. Biodegradability, high permeability, nontoxic to humans, and cost-effectiveness are the features which make chitosan NPs unique. Chitosan and its derivatives have attracted considerable attention due to their biocidal activities [74, 75]. Several authors have reported the beneficial application of chitosan and its oligosaccharides which includes antitumor [76], neuroprotective [77], antimicrobial [78–85], and anti-inflammatory [86] agents. **Table 2** summarizes the fungicidal activities of chitosan against important agricultural microorganisms contaminating

Fungal decay on pear fruit was suppressed by the combination of chitosan, yeast antagonist *Cryptococcus laurentii*, and CaCl2. The results showed that mixture of chitosan at 0.5% and *C*. *laurentii* exerted greater effects compared to chitosan or *C*. *laurentii* alone. CaCl2 showed little antifungicidal activity; however, it combination with chitosan and *C*. *laurentii* led to an effective and stable reduction of fungal decay [87], thus minimize or eradicate the menace of postharvest losses. Anthracnose in papaya caused by *Colletotrichum gloeosporioides* was controlled by the combination of *Burkholderia cepacia*, chitosan (0.75%) and CaCl2 [88]. Postharvest blue, green, and grey molds affecting apple, oranges, and lemons were effectively controlled by mixing glycol chitosan (0.2%) with *Candida saitoana* [89–91]. Ag/ chitosan-NPs showed significant antifungal activity against *A*. *flavus*, *A*. *alternata*, and *R*. *solani* hence could be used during grain storage [92, 93]. The synergistic effect (fungicidal activities) of hybrid copper(II) chitosan NPs to inhibit the growth of *F*. *graminearum*, *Verticillium dahlia* 57, and *F*. *solani* 169 was reported. In both cases, the NPs exerted an excellent efficacy in repressing the growth of fungi [94, 95]. Other authors reported that certain strains of *A*. f*lavus*, *Cladosporium cladosporioides*, *P*. *aurantiogriseum*, and *Torulaspora delbrueckii* were resistant to chitosan at levels as high as 1% [7, 96]. The application of chitosan (0.025 and 0.05%) was effective against *Saccharomycodes ludwigii* and *Saccharomyces exiguous*. A rapid reduction in the

number of yeast colonies was observed 2–4 min after application [97].

**3.1 Mechanistic action of chitosan nanoparticle antimicrobial activity**

According to literature [116, 117], chitosan is composed of polycationic copolymers, with glucosamine and N-acetylglucosamine as axillary units, which contributes to its antimicrobial activity. The difference in environmental pH, pKa

and its potential application in postharvest control.

According to an earlier report, the effectiveness of the biocidal activity of chitosan depends on the molecular weight, degree of acetylation, and concentration [98, 99]. The application of NPs coated with polyethylene glycol (PEG) and natural garlic oil against *Tribolium castaneum*, a vital storage pest showed high efficiency over an extended period (8 months) due to the slow and persistent release of the active components [100]. The study highlighted the potential application of PEG-NPs as capsules to encapsulate various natural bioactive ingredients (i.e., oil from *Azadirachta indica*, extracts of *Khaya anthotheca*, alkaloid extracts of *Piper guineense* [101], etc.) for controll release and subsequent killing of microorganisms and pests during grain storage. Furthermore, [102, 103] extensively reviewed the literature on the biocidal activities of natural compounds (i.e., herbs, species, etc.)

**140**

