Agriculture Reference
In-Depth Information
2.
P
HOTOCATALYTIC
S
TERILIZATION
In 1980s, Japanese scientist first found the photocatalytic sterilization
function of nano-TiO
2
under the irradiance of ultraviolet light [7,8]. After
demonstration of microbiocidal effects on
Escherichia coli
, the responses of a
wide spectrum of organisms including viruses, bacteria, fungi, algae, and
cancer cells to photocatalytic reactions of nano-TiO
2
were investigated [9,10].
Antibacterial role of nano-TiO
2
were intensively studied recently for
prevention and cure of agricultural diseases. Li et al. (2008)
[11]
examined the
nano-Ti0
2
semi conductor sol has excellent antibacterial effect on plant
pathogens, and the antibacterial rate increases in time course
．
The results of
relative antibacterial rate show that when the illumination lasts for 24h, the
relative antibacterial rate reaches 100
％
. So nano-TiO
2
semiconductors sol is a
potent and broad spectrum antibacterial. The impact of nano-TiO
2
to the
phyllosphere bacterial community were assessed using culturable-depend and
PCR-DGGE methods
[12]. Results showed mat quantities of the culturable
phyllosphere bacteria were reduced from 1.8x10
-7
to 3.1x10
-6
cfu/g with the
increasing concentrations of the nano-TiO
2
from 0.002 to 20mg/mL. The
diversity of the phyllosphere bacteria was also analyzed by PCR-DGGE.
When the concentrations of the nano-TiO
2
were higher than 0.02 mg/mL
，
the
DGGE bands was significantly lower than that of the contro1. Sequencing
results of the bands from the DGGE gel showed that there were at least 7
bacterial genera on the cucumber phyllosphere. But only one phyllosphere
uncultured bacterium was not influenced by the concentration of the nano-
TiO
2
．
Numerous applications to control food and postharvest pathogens,
sterilization of
E. coli
and its endotoxin decomposition by TiO
2
powder, TiO
2
slurry and TiO
2
thin film surface have been reported [7,8,13,14]. Anti-bacterial
role of nano-TiO
2
were intensively studied for post-harvest disease control of
vegetables and fruits to prevent rotting. Maneerat and Hayata (2006)
[15]
showed that TiO
2
photocatalytic reaction in the form of TiO
2
powder and
TiO
2
coated on a plastic film inhibited against
Penicillium expansum in vitro
and in fruit tests. Our findings suggest that TiO
2
photocatalytic reaction shows
antifungal activity against
P. expansum
which may have potential for
postharvest disease control.
