TATIANE VIANA DUTRA

Título da Tese: ALICYCLOBACILLUS ACIDOTERRESTRIS:FORMAÇÃO DE BIOFILMES E INIBIÇÃO DO SEU CRESCIMENTO EM SUCO DE LARANJA POR NANOPARTÍCULAS DE CURCUMINA

 Orientador: Prof. Dr. Benício Alves de Abreu Filho

Data da Defesa:13/04/2022

RESUMO GERAL

GENERAL ABSTRACT
INTRODUCTION
Alicyclobacillus spp. are Gram-positive, spore-forming bacillus with the ability to
adhere to surfaces and form biofilms, associated with the deterioration of acidic
beverages such as orange juice. There are more than 25 species identified
(Sokołowska et al., 2020), among them A. acidoterrestris, which is capable of
producing guaiacol, which is responsible for the astringent taste in contaminated
juices. This microorganism has been used as a quality parameter in the production of concentrated orange juice; therefore, it is necessary to search for alternatives for its control, mainly in Brazil, where the production and exportation of juice is of great economic importance. In this sense, the improvement of studies on its development on different surfaces is justified, in addition to the association of encapsulation techniques of natural compounds, development of nanoparticles, in order to improve its stability and potentiate its antibacterial effects.
GOALS
The objectives of this work were: evaluate the interference of the initial microbial
load on the biofilm formation of Alicyclobacillus acidoterrestris on the surfaces
of AISI 304 stainless steel and food grade natural rubber under two temperature
conditions, 28 °C and 45 °C, as well as the spore load in both conditions. And
evaluate the use of nano encapsulated curcumin as an antimicrobial against
different strains of Alicyclobacillus spp. and other pathogenic bacteria, in addition
to analyzing their physical characteristics, encapsulation efficiency, curcumin
bioactive properties and toxicity; and as proof of concept the interference in the
properties of orange juice, such as pH, color and °Brix.
MATERIAL AND METHODS
The strain A.acidoterrestris (CBMAI 0244T) (DSMZ 3922, Deutsche Sammlung
von Mikroorganismen und Zellkulturen, Germany) was used for biofilm
formation; the surfaces used were AISI 304 stainless steel and food grade natural rubber, both measuring 8mm x 8mm x 3mm. And the concentrated orange juice (66 °Brix) was reconstituted to 11 °Brix with sterile water.
Microbial concentrates (2 log CFU/mL and 5 log CFU/mL) were prepared at two
incubation temperatures (28 and 45 °C) in reconstituted juice, and confirmed by
control in BAT broth. Biofilm formation and evaluation were carried out at times
0, 4, 8, 24, 48 and 72 hours, taking into account the cleaning times of industrial calorimetry (DSC) analyzes prove the effectiveness of the encapsulation. The images obtained by transmission electron microscopy (TEM) showed a wide range of nanoparticle sizes. The antioxidant activity assay confirmed the bioactive properties of encapsulated curcumin and also its non-cytotoxicity against four carcinoma and two non-tumor cell lines. The stability of the juice added to the nanoparticles was confirmed by maintaining their pH, color and ºBrix after 3 days of storage at 8 °C, refrigerated temperature.
CONCLUSIONS
Greater biofilm formation was observed with the highest initial microbial load on
the two contact surfaces analyzed, steel and rubber, at both temperatures, but when the contact time was taken into account, there was greater formation on the rubber surface. As the formation of biofilm has already been observed after 4 hours of contact, it is necessary to perform hygiene procedures frequently. Regarding the spores, they showed greater ease of adhesion on the stainless-steel surface, with a high presence from the highest initial concentration of microorganisms. Regarding the use of curcumin nanoparticles as antimicrobial agents, the result was satisfactory, as it proved their antimicrobial and antibacterial effect against the tested strains; in addition to the stability of the nanoparticle being confirmed by the tests performed. Keywords: Alicyclobacillus, spores, orange juice, biofilm, curcumin, nanoparticles.

Artigos Publicados Vinculados a Tese:

https://doi.org/10.1590/0103-8478cr20190790
https://doi.org/10.1016/j.ijfoodmicro.2021.109442