Natural Biocides Research Articles

Eco-Friendly Antimicrobial Finishing of Natural Fibres

Natural fibres well protected against biodeterioration and with barrier properties can be used in many new applications. The study aims at using eco-friendly biocides, not used in textile industry so far, for antimicrobial finishing of natural fibres. The research was carried out on flax fibre and linen fabric protected with biocides based on amono-boron-copper compounds, natural biocides and ionic liquids as new QACs. The flax fibre was subjected to action of mixture of fungi most often causing decomposition of cellulose in high humidity conditions. Evaluation of antibacterial properties of treated fabrics was done using qualitative method in presence of synthetic sweat against groups of bacteria present on human skin.

Chemical Composition and Fungitoxic Activity of Essential Oil of Thuja orientalis L. Grown in the North-Western Himalaya

The essential oil from fresh leaves of Thuja orientalis L. grown in the north-western Himalaya was isolated by means of hydrodistillation and analyzed by GC and GC/MS. Twenty-two compounds representing 94.0% of the total oil were identified. The leaf oil contained alpha-pinene (29.2%), Delta-3-carene (20.1%), alpha-cedrol (9.8%), caryophyllene (7.5%), alpha-humulene (5.6%), limonene (5.4%), alpha-terpinolene (3.8%) and alpha-terpinyl acetate (3.5%) as major constituents. The essential oil showed antifungal activity against Alternaria alternata in a direct bioautography assay. Two main bioactive compounds named as b1 (Rf = 0.54) and b2 (Rf = 0.80) were observed and tested for antifungal activity; they produced an inhibition zone of 5 and 10 mm in diameter, respectively. The components b1 and b2 were further purified by preparative thin layer chromatography and their antifungal efficacy was re-tested. The minimum inhibitory amount (MIA) of b1 and b2 against A. alternata was determined as 30.5 and 4.5 microg, respectively, using a bioautography assay. The bioactive constituent corresponding to b1 was determined as alpha-cedrol by using GC/MS analysis. The potential of essential oils as a source of natural biocides is discussed.

Application of marine biotechnology in the production of natural biocides for testing on environmentally innocuous antifouling coatings

The widely recognized biofouling phenomenon has many negative consequences for artificial structures that are in contact with seawater in the form of structural defects and additional expenses for maritime companies due to cleaning and prevention processes. After having analyzed the serious environmental problems caused by an indiscriminate use of highly toxic biocides coming from organic derivatives of tin compounds and the uncontrolled emissions of volatile organic compounds (VOC) to the atmosphere, the evolving technology of antifouling paintings (further mandated by current environmental standards) aims to develop environmentally innocuous water-based coverings in which extracts of the very same marine world are used as biocide compounds. Water-based coatings are being developed that use low-toxic elements and natural biocides, where bacteria is isolated from surfaces immersed in the marine environment, creating a promising source of natural antifouling compounds. The result is a new environmentally friendly antifouling coating that is able to mitigate the problem of biofouling without affecting the surrounding medium, and which may be applied on any artificial structure in contact with seawater.

Application of marine biotechnology in the production of natural biocides for testing on environmentally innocuous antifouling coatings

Application of marine biotechnology in the production of natural biocides for testing on environmentally innocuous antifouling coatings

Screening of Natural Product Biocides for Control of Non-indigenous Species

Several benzo-, naphtho- and anthraquinones were tested for their efficacy as biocides in controlling aquatic nuisance species in ships' ballast water. A requirement of this application was broad spectrum aquatic toxicity, coupled with a relatively rapid rate of degradation, in order to comply with coastal discharge requirements. Compounds were screened using a suite of toxicity bioassays designed to establish their relative toxicity to an array of planktonic organisms including larval bivalves Dreissena and Crassostrea, various developmental stages of the estuarine copepod Eurytemora affinis, brine shrimp larvae (Artemia salina), the freshwater invasive water flea Bythotrephes, larval sheepshead minnows (Cyprinodon variegates) and two unicellular algal genera Isochrysis and Neochloris.. The majority of the data were recorded as the lowest concentration of the test compound resulting in complete mortality or inactivation of test organisms (LC 100(99)). The naphthoquinones juglone, plumbagin, menadione and naphthazarin showed the highest toxicity to the broadest range of organisms, often at levels much less than 1 mg l−1, and most of the attention was focused on this group. While plumbagin and juglone appeared overall to be the most toxic compounds, it was concluded that menadione was probably the most cost-effective candidate compound for shipboard use for controlling invasive species in ballast water, particularly in view of the large volumes of water that would require treatment.

Comparative antibacterial activity of polymeric 3-alkylpyridinium salts isolated from the Mediterranean sponge Reniera sarai and their synthetic analogues

Metabolites from marine sponges are considered a promising alternative to heavy metals in antifouling coatings. Water-soluble polymeric 3-alkylpyridinium salts and 14 related synthetic analogues showed considerable antibacterial activity against marine biofilm bacteria and may represent good candidates as natural biocides for marine technology applications.

Effect of industrial and natural biocides on spoilage, pathogenic and technological strains grown in biofilm

This study aimed at investigating bactericide solutions effective on spoilage and pathogenic bacteria while preserving technological bacteria. Two compounds of essential oil (thymol and eugenol), one essential oil of Satureja thymbra and two industrial biocides (PE 270–30, Brillo) were tested on technological strains ( Staphylococcus equorum, Staphylococcus succinus and Lactobacillus sakei) grown in monoculture biofilm and on a mixed biofilm of pathogenic bacteria ( Staphylococcus aureus, Listeria monocytogenes) and spoilage bacteria ( Pseudomonas fragi, Escherichia coli). Biofilm cultures were performed in glass fibre filters for 24 h at 20 °C before application of biocides. Thymol and eugenol had no effect on the mixed biofilm. S. thymbra (2%) was highly effective on spoilage strains (5 log reduction), and S. equorum (4 log reduction) was moderately effective on pathogens (2.3 log reduction) and not effective on S. succinus and L. sakei (0.5 log reduction). PE-270-30 with 10% Na 2 SO 4 decreased spoilage bacteria (5.1 log reduction), maintained the technological bacteria, but did not reduce the pathogens. The disinfectant Brillo (3%) killed all the strains. These results showed the difficulty in obtaining a biocide that is effective in destroying spoilage and pathogenic bacteria while preserving technological bacteria. Essential oils could be a good alternative for eradicating spoilage bacteria in the food environment where they are often found at high levels.

Antibacterial effects of knotwood extractives on paper mill bacteria.

Hydrophilic knotwood extracts from 18 wood species were assessed in disc diffusion and liquid culture tests for antibacterial effects against three species of paper mill bacteria. The Pinus sylvestris, P. resinosa, P. contorta, and P. banksiana extracts decreased or inhibited bacterial growth. The susceptibility order was P. sylvestris > P. resinosa > P. contorta > P. banksiana, correlating with the concentrations of pinosylvin and pinosylvin monomethyl ether in these wood species. Also, Pseudotsuga menziesii and Thuja occidentalis extracts had a small inhibitory effect. The Gram-positive Bacillus coagulans was more susceptible to the extracts than the Gram-negative Burkholderia multivorans and Alcaligenes xylosoxydans. The main components in the Pinus knotwood extracts were pinosylvin monomethyl ether and pinosylvin, suggesting these to be the active components. Therefore, pure pinosylvin, pinosylvin monomethyl ether, and dihydro-pinosylvin monomethyl ether were also tested. All compounds showed antibacterial effects. However, higher concentrations were needed for these pure compounds than for the knotwood extracts. Pinosylvin had stronger antibacterial effects than pinosylvin monomethyl ether. This work shows that knotwood extracts, especially from Pinus species, have a potential for use as natural biocides in papermaking.

Prevention and protection of the effects of biocorrosion and biofouling minimizing the environmental impact

Biocorrosion and biofouling processes are mediated by microorganisms adhered to the metal surfaces or embedded in a gelatinous matrix called biofilm. Biofilms affect the interaction between metals and the environment not only in deleterious processes like corrosion but also in several biological processes applied to materials recovery and handling. The growth of the microorganisms capable to induce biocorrosion is conditioned by favorable environmental conditions. However, the chemical agents generally used to prevent or protect metallic structures from biocorrosion are highly toxic and after use can have a negative impact on the environment. Four different approaches developed in our laboratory to prevent and control biocorrosion but minimizing the environmental impact, are successively presented in this paper: a) the use of ozone as an environmentally friend biocide for cooling water systems; b) the assay of the effectiveness of natural biocides on planktonic and sessile bacteria; c) the potential use of film forming corrosion inhibitors; d) the use of innovative preventing substances.

Efficacy of Chitosan, Carvacrol, and a Hydrogen Peroxide–Based Biocide against Foodborne Microorganisms in Suspension and Adhered to Stainless Steel

The ability of natural compounds to inactivate foodborne organisms adhered to surfaces was investigated with the ultimate aim of replacing synthetic biocides by more environmentally friendly, natural alternatives. The antimicrobial efficacy of 0.5, 1.0, and 2.0% chitosan and Spor-Klenz RTU (a commercial biocide based on hydrogen peroxide and peroxyacetic acid) and 0.5, 1.25, and 2.0mM carvacrol was determined at 20°C against Listeria monocytogenes, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Saccharomyces cerevisiae adhered to stainless steel disks. Treatment with up to 2.0% chitosan reduced the viable cell count in the microbial films of the four test organisms by 2.4, 1.8, 2.3, and 0.9 log CFU/test surface (t.s.), respectively. By contrast, planktonic counts of the same organisms were reduced by 0.8 to 1.7 log CFU/ml at 2.0% chitosan. Treatment with 2mM carvacrol reduced the viable counts of adhered listeriae, salmonellae, and yeasts by 2 to 3 log CFU/t.s. but S. aureus counts were reduced by only 0.9 log CFU/t.s. The efficacy of any single compound was species specific. In the case of microbial films prepared using listeriae and salmonellae, Spor-Klenz RTU was most biocidal, followed by carvacrol and then chitosan. However, dried films of S. aureus were most sensitive to chitosan and relatively resistant to carvacrol and Spor-Klenz RTU. By contrast, yeast films were most sensitive to carvacrol and least sensitive to chitosan. It was concluded that carvacrol and chitosan may have potential for use as natural biocides although optimization of conditions would be necessary.

Analysis of benzothiazole in Italian wines using headspace solid-phase microextraction and gas chromatography-mass spectrometry.

Benzothiazoles are a part of the molecular structure of a large number of natural products, biocides, drugs, food flavors, and industrial chemicals. They also appear in the environment mainly as a result of their production and use as rubber vulcanization accelerators. A new headspace solid-phase microextraction (HS-SPME) method for analysis of benzothiazole (BTH) in wine is described. This method is fast, inexpensive, and does not require solvents. The detection limit of BTH in wine was 45 ppt with linearity up to 100 ppb. The quantification of BTH is performed by the standard additions method and does not require the use of an internal standard. We have analyzed 12 wines from different grape varieties grown in several regions, using SPME extraction and gas chromatography-mass spectrometry (GC-MS) detection. Under these experimental conditions, benzothiazole was found in all wines analyzed. Concentration levels in samples varied from 0.24 microg/L (Vermentino) to 1.09 microg/L (Franciacorta).

Distribution and Accumulation of Thiophenes in Plants and Calli of DifferentTagetesSpecies

Ketel, D. H. 1987. Distribution and accumulation of thiophenes in plants and calli of different Tagetes species.—J. exp. Bot. 38: 322-330. The diversity of thiophenes (natural biocides) and the differences between the concentrations of these compounds in the leaves and roots of Tagetes erecta L., T.patula L. cv. Nana furia, and T. minuta L. (marigolds) indicated the presence of at least two different sites of accumulation: leaves and roots. Leaf expiants of Tagetes, however, are used by preference to obtain callus cultures. Once subcultured, secondary (C2) calli of T. patula obtained from leaves of 4 to 7-week-old plants, contained higher amounts of accumulated thiophenes (up to 80% of the amounts in the leaves) than original (C,) or twice subcultured calli (C3). The concentrations of thiophenes in C2 calli of T. minuta were about half those of C! calli, while the concentrations of thiophenes of C, calli amounted to 1-2% of the leaf values. Most of the C3 calli of T. minuta did not contain thiophenes at all. Although C3 calli of T. erecta also contained considerable amounts of thiophenes, the C2 calli died, most likely owing to high levels of accumulated polyphenolic compounds. The combination of species effects and the physiological state of plants and calli provides adequate information to decide whether Tagetes calli are able to produce thiophenes or not. It is concluded that the ability to produce thiophenes does not depend on the organ used, but on the genetic information present in the species, and on the physiological state of plants and calli, particularly their age.

Inorganic Nutrition of Callus Tissues of Tagetes Species: The Effects on Morphogenesis and Accumulation of Thiophenes and other Non-polar Secondary Metabolites

Summary The formation and morphology of callus were studied on leaf explants of Tagetes patula and Tagetes minuta , inserted into three different solid media with the inorganic composition of media used for soilless culture of intact plants, or into MS-medium Callus formation responded differently to the type of medium and plant species. On all «plant media» callus formation occurred in only one of the two species. Which species died and which species proliferated depended on the type of medium. Growth of calli was curtailed on plant culture media as compared with MS-medium. However, transfer of secondary calli from plant culture media to fresh MS-medium restored a high rate of growth. Calli of T. patula had a higher level of non-polar metabolites and thiophenes (natural biocides from Tagetes plants) than calli of T. minuta . In T. patula calli the content of non-polar metabolites increased from primary to secondary callus and was highest when MS-medium was used. In contrast, T. minuta calli showed a decrease in non-polar metabolite content upon subculturing and this content was lowest on MS-medium. These trends of the content of non-polar secondary metabolites paralleled the trends in morphological differentiation that were observed when calli were cultured continuously on MS-medium (Ketel, Physiol. Plant. 66 [1986], 392) and confirm the positive correlation between morphological and biochemical differentiation. It is concluded that the inorganic composition of the medium affected secondary metabolism only to a quantitative extent and that a correct inorganic composition of the medium together with the choice of the most suitable species are essential in the production of desired secondary metabolites in vitro.

Pest Pressure and Recombination Systems in Plants

An open recombination system would be of immediate and manifest value to plant species experiencing pathogen and pest pressures which are intense, systematic, and capable of redirection in the event the host alters its defensive posture. These pressures are most important in climax communities, well exemplified in the tropics and on ancient islands, where open recombination prevails and is promoted. The simple genetic bases for host resistance and pathogen or pest virulence, the vulnerability of species with restricted recombinations to disease epidemics and pest outbreaks, and the ability of pathogens and pests to rapidly evolve resistance to new natural or synthetic biocides provide the empirical superstructure for postulating why the genomes of K-selected species do not congeal.