Narrow Results

This work reports on the axial coordination of zinc phthalocyanine and bis-(1,6-hexanedithiol) silicon phthalocyanine to silver and gold nanoparticles. Red shifting of absorption spectra of the phthalocyanine complexes was observed after conjugation with the nanoparticles. An improvement in the photophysicochemical behavior and antimicrobial activity was achieved in the presence of metal nanoparticles for both complexes. A decrease in triplet lifetimes was observed for all the phthalocyanine metal nanoparticle conjugates. The Zn phthalocyanine complex gave the highest triplet and singlet oxygen quantum yield in the presence of gold nanoparticles. On the other hand, the bacterial inhibition was found to be best for the Si phthalocyanine derivative in the presence of nanoparticles compared to the Zn phthalocyanine counterpart. The highest antimicrobial activity was achieved for both conjugates against B. subtilis compared to S. aureaus both in the dark and under illumination with light.

The modification of polyethylene terephthalate (PET) fibres from used beverage bottles was investigated by treatment with UV (6 and 36h), temperature (35°C and 50°C), and without physic treatment on the production of extracellular enzymes, and biofilm formation by Bacillus subtilis under controlled conditions. The results showed partial degradation of the copolymer submitted to physic treatments and colonization by B. subtilis. The best results of degradation were associated with protease, amylase and esterase on surface of PET particles submitted to 50°C of temperature, during 60 days. However, the esterase activity simulating biodegradation of PET by B. subtilis, and suggest residual lost of weight, and the products showed low toxicity when compared with the PET particles without treatments.

In order to prolong the shelf-life of the minced fish products at room temperature, a novel combined sterilization method was proposed. Bacillus subtilis was chosen as the indicator bacteria, because it is one of the most heat-resistant bacteria probably exists in fish products. A self-made ohmic heating system was used to inactivate the indicator bacteria in the surimi firstly. After sterilized by ohmic heating system, the samples were vacuum-packed and put into an incubator at 35 °C for several hours to give the favorable growth condition to the remained spores of Bacillus subtilis. Then the second sterilization can proceed – heating them by boiling water for several minutes. Response Surface Design was used to determine the optimal sterilization parameters including: electric field intensity 40 V/cm, sterilization time of ohmic heating 5 min, culture time in an incubator 12 h, and heating time by boiling water 25 min. The results demonstrated that the minced fish products with high sensory quality and having 15 days the shelf-life at the room temperature can be obtained by using the proposed sterilization method.