Use of Polyguanidine-Derivatives-Based Biocides for Microbial Growth Inhibition and for the Development of a Novel Polyethylene-Based Composite Material Resistant to the Formation of Multispecies Microbial Biofilms

This study aimed to investigate the dependence of the biocidal activity of polyguanidine (co)polymers on their structure during the formation of biofilms by active PE-degrading cultures of model microorganisms. The Bc-2 copolymer of methacryloyl guanidine hydrochloride (MGHC) and diallyldimethylammonium chloride (DADMAC), which suppressed both the formation of biofilms and the growth of planktonic cultures, exhibited the highest activity. When PE was exposed in tropical soil, the composition of the microbial community on the PE surface differed significantly from that of the community in the surrounding soil. In particular, the proportion of Actinobacteria increased from 7% to 29%, while the proportion of Bacteroidetes decreased from 38% to 8%. Keywords: biofilms, polyhexamethylene guanidine salts, dynamics of biofilm formation, antibiofilm effect, composite materials

Phytochemistry and GC-MS Screening and Biocidal Potentiality of Ginger (Zingiber officinale) Rhizome against Mosquito’s Larvae

Mosquitoes can act as vectors for many viruses and parasites through carrying these organisms from person to person. Although great number of natural products are lethal to mosquitoes, but few researches are conducted to understand the magnitude of the behavioral response to these plant parts. The objectives of this study were to screen the phytochemical and other chemical components from ginger rhizome in addition to test their aqueous and ethanol extracts on mosquito’s larvae. The standard methods, materials and devices were used to screen the phytochemical components and the chemical constituents (GC-MS). The aqueous and the ethanol extracts from clove pods were prepared and used against Anopheles, Culex and Aedes larvae. The results of the aqueous extract showed that, the LC50 was 153.77 mg/L for Anopheles larvae, 179.05 mg/L for Culex larvae, and 208.37 mg/L for Aedes larvae, also the ethanol extract of ginger rhizome was more potent than the aqueous extract. The biocidal activity can be attributed to the presence of saponins, flavonoids, glycosides, alkaloids and steroids. The GC-MS for the hexane extract showed the presence of alkaloid: gingerol (18%) and eugenyl acetate- (19%) that gives the sweet aromatic, spicy taste, but the ethanol extract detected gingerol (43%) and zingiberene (14%). The obtained data will be useful to understand the mechanisms and reasons of biocidal activity of ginger rhizome against the tested mosquito’s larvae.

Impact of Physico-Chemical Properties of Cellulose Nanocrystal/Silver Nanoparticle Hybrid Suspensions on Their Biocidal and Toxicological Effects

There is a demand for nanoparticles that are environmentally acceptable, but simultaneously efficient and low cost. We prepared silver nanoparticles (AgNPs) grafted on a native bio-based substrate (cellulose nanocrystals, CNCs) with high biocidal activity and no toxicological impact. AgNPs of 10 nm are nucleated on CNCs in aqueous suspension with content from 0.4 to 24.7 wt%. XANES experiments show that varying the NaBH4/AgNO3 molar ratio affects the AgNP oxidation state, while maintaining an fcc structure. AgNPs transition from 10 nm spherical NPs to 300 nm triangular-shaped AgNPrisms induced by H2O2 post-treatment. The 48 h biocidal activity of the hybrid tested on B. Subtilis is intensified with the increase of AgNP content irrespective of the Ag+/Ag0 ratio in AgNPs, while the AgNSphere−AgNPrism transition induces a significant reduction of biocidal activity. A very low minimum inhibitory concentration of 0.016 mg AgNP/mL is determined. A new long-term biocidal activity test (up to 168 h) proved efficiency favorable to the smaller AgNPs. Finally, it is shown that AgNPs have no impact on the phagocytic capacity of mammalian cells.

Microbial Toxins in Insect and Nematode Pest Biocontrol

Invertebrate pests, such as insects and nematodes, not only cause or transmit human and livestock diseases but also impose serious crop losses by direct injury as well as vectoring pathogenic microbes. The damage is global but greater in developing countries, where human health and food security are more at risk. Although synthetic pesticides have been in use, biological control measures offer advantages via their biodegradability, environmental safety and precise targeting. This is amply demonstrated by the successful and widespread use of Bacillusthuringiensis to control mosquitos and many plant pests, the latter by the transgenic expression of insecticidal proteins from B. thuringiensis in crop plants. Here, I discuss the prospects of using bacterial and fungal toxins for pest control, including the molecular basis of their biocidal activity.

Tambjamines and Prodiginines: Biocidal Activity against Trypanosoma cruzi

The aim of this work was to explore new therapeutic options against Chagas disease by the in vitro analysis of the biocidal activities of several tambjamine and prodiginine derivatives, against the Trypanosoma cruzi CLB strain (DTU TcVI). The compounds were initially screened against epimastigotes. The five more active compounds were assayed in intracellular forms. The tambjamine MM3 and both synthetic and natural prodigiosins displayed the highest trypanocidal profiles, with IC50 values of 4.52, 0.46, and 0.54 µM for epimastigotes and 1.9, 0.57, and 0.1 µM for trypomastigotes/amastigotes, respectively. Moreover, the combination treatment of these molecules with benznidazole showed no synergism. Finally, oxygen consumption inhibition determinations performed using high-resolution respirometry, revealed a potent effect of prodigiosin on parasite respiration (73% of inhibition at ½ IC50), suggesting that its mode of action involves the mitochondria. Moreover, its promising selectivity index (50) pointed out an interesting trypanocidal potential and highlighted the value of prodigiosin as a new candidate to fight Chagas disease.