26-05-2012, 04:19 PM
Preliminary Study and Improve the Production of Metabolites
with Antifungal Activity by A Bacillus Sp Strain IBA 33
Preliminary Study.pdf (Size: 463.34 KB / Downloads: 67)
Abstract:
Bacillus sp strain IBA 33 metabolites, isolated from decaying lemon fruits, were evaluated for the control of
pathogenic and non-pathogenic fungi (Penicillium digitatum, Geotrichum candidum, Penicillium expansum, Aspergillus
clavatus, Aspergillus fl avus, Aspergillus niger, and Fusarium moniliforme). These metabolites were recovered from Landy
medium (LM) without aminoacids. In order to optimize metabolites production the LM was modifi ed by adding different
concentrations and sources of amino acids and carbohydrates at different culture conditions.
Introduction
One of the greatest causes of loss in the food industry is postharvest diseases of fruits and vegetables.1
According to U.S.A. estimations this loss reaches 24%2 whereas it may climb to 45%–50% in developing
countries,3 but loss has generally been considered to be approximately 10% to 40% depending on
packinghouse technology.4
Fungi are the principal decaying agents in fruit kept in cold storage chambers for long periods.5
Postharvest lemon diseases are mainly caused by Penicillium italicum (blue mold), Penicillium digitatum
(green mold), Geotrichum candidum (sour rot), Alternaria citri (black mold) and Fusarium sp.6
Postharvest fruit diseases are controlled with careful manipulation practices and synthetic fungicides
like 2–4 thiazalil benzimidazole and imidazole. This method is more widely used against fungal decay
because of its low cost and easy application. However, it presents manifold objections since prolonged
use generates resistance to synthetic fungicides by major postharvest pathogens7,8 and increases chemical
remainders in fruits with the consequent potentiality engendering iatrogenic diseases.9 In addition, there
is strong pressure from the consumers who demand products of greater quality, but with a smaller
amount of chemical agents and a major environmental protection.10 A desirable alternative to the use
of synthetic fungicides is the application of a biological control of phytopathogenic fungi.
There are many microorganisms like Pseudomona, Gliocladium, Trichoderma, Criptococcus,
Rhodotorula and Bacillus11 with antagonistic activity against phytopathogenic fungi.
Currently there are several formulations of Bacillus subtilis in the market to eradicate postharvest
diseases of rice, beans, tomato and avocado pears,11 but there are no data about biological control of
lemon phytopathogenic fungi using microorganisms of the region where such citric fruits are grown.
In this work we studied the production and optimization of metabolites by a strain of Bacillus sp
IBA 33 with antifungal activity and their effectiveness in controlling decaying lemon fruit fungi. The
microorganism was isolated from the soil of lemon plantations of Tucumán, Argentina.
Materials and Methods
Microorganisms
Bacterial strain
The Bacillus strain used in this paper was isolated
from the soil of a lemon plantation of Tucumán,
Argentina and maintained in bevel tubes with
nutrient agar pH 7.2. The microorganism was
taxonomically identifi ed in genus by phenotypic
tests (Gram stain, morphology, catalase activity,
nitrate reduction, indole production, motility,
growth at 7% NaCl, acid production, gelatinase
and starch hidrolysis). The bacilli identifi cation
was performed by the standard tests described
in the Bergey’s Manual of Determinative
Bacteriology.12 Microscopic disposition, growth
at 65 °C were assayed to identify this group.
Discussion
The results of the present study show that Bacillus
sp strain IBA 33 produces one or more metabolites
with antifungal action against different phytopathogenic
and non pathogenic fungi. The metabolites
were heat-resistant because they conserved the
same antifungal activity after sterilization at 121 °C
for 10 min. That fact was reported in previews
works.20