Synthesis, fungal biotransformation, and evaluation of the antimicrobial potential of chalcones with a chlorine atom.

Chalcones are intermediate products in the biosynthesis of flavonoids, which possess a wide range of biological properties, including antimicrobial and anticancer activities. The introduction of a chlorine atom and the glucosyl moiety into their structure may increase their bioavailability, bioactivity, and pharmacological use. The combined chemical and biotechnological methods can be applied to obtain such compounds. Therefore, 2-chloro-2'-hydroxychalcone and 3-chloro-2'-hydroxychalcone were synthesized and biotransformed in cultures of two strains of filamentous fungi, i.e. Isaria fumosorosea KCH J2 and Beauveria bassiana KCH J1.5 to obtain their novel glycosylated derivatives. Pharmacokinetics, drug-likeness, and biological activity of them were predicted using cheminformatics tools. 2-Chloro-2'-hydroxychalcone, 3-chloro-2'-hydroxychalcone, their main glycosylation products, and 2'-hydrochychalcone were screened for antimicrobial activity against several microbial strains. The growth of Escherichia coli 10,536 was completely inhibited by chalcones with a chlorine atom and 3-chlorodihydrochalcone 2'-O-ß-D-(4″-O-methyl)-glucopyranoside. The strain Pseudomonas aeruginosa DSM 939 was the most resistant to the action of the tested compounds. However, chalcone aglycones and glycosides with a chlorine atom almost completely inhibited the growth of bacteria Staphylococcus aureus DSM 799 and yeast Candida albicans DSM 1386. The tested compounds had different effects on lactic acid bacteria depending on the tested species. In general, chlorinated chalcones were more effective in the inhibition of the tested microbial strains than their unchlorinated counterparts and aglycones were a little more effective than their glycosides.

Functional Properties of Chitosan Oligomers Obtained by Enzymatic Hydrolysis.

The aims of this study were to obtain chitooligosaccharides (COS) from chitosan (CH) with improved functional properties and comparison of the use of two different enzymes: commercial cellulase (CL) and the dedicated enzyme chitosanase (CS). After enzymatic reaction, chitosan oligomers (NFs) were isolated by methanol into two fractions: precipitate (HMF) and supernatant (LMF). The occurrence of a hydrolysis reaction was confirmed by an increased reducing sugar content and viscosity reduction of chitosan oligomers. CPMAS 13C NMR analysis confirmed the dissimilar cleavage mechanism of the enzymes used. LMF and NF fractions were characterised by improved solubility in water (94.56%) compared to the HMF and CH samples (70.64%). Thermogravimetric analysis (TGA) showed that the HMF decomposed in two-stage process while CH, NF, and LMF decomposed in a three-stage process. The greatest mass loss of LMF samples (58.35%) suggests their sensitivity to high-temperature treatments. COS were a mixture of DP (degrees of polymerisation) from 3 to 18 hetero-chitooligomers, with an average Mw of <3 kDa. CL consisted of more low-DP products (DP 3-7) than COS made with CS. LMF characterised by DP~2 showed lower DPPH radical scavenging activity than HMF and NF with DP 3-7. The ability to reduce Escherichia coli increased in the given order: LMF > NF > HMF > CH.

Chalcone-Derived Lactones: Synthesis, Whole-Cell Biotransformation, and Evaluation of Their Antibacterial and Antifungal Activity.

Four compounds with lactone moiety were synthesized from chalcone 1 in three- or four-step synthesis. γ-Bromo-δ-lactone 5 was the only product of bromolactonization of acid 4 whereas bromolactonization of ester 3, apart from lactone 5 also afforded its isomer 6 and two diastereoisomeric δ-hydroxy-γ-lactones 7 and 8. Lactone 8 was also obtained in 88% yield as a product of simultaneous dehalogenation and translactonization of γ-bromo-δ-lactone 5 by Penicillum frequentans AM 359. Chalcone-derived lactones 5-8 were subjected to the tests on antimicrobial activity and the results compared with activity of starting chalcone 1. Obtained lactones 5-8 in most cases limited the growth of tested bacterial and fungal strains. The highest activity was found for δ-hydroxy-γ-lactone 8 which completely inhibited the growth of Staphylococcus aureus, Fusarium graminearum, Aspergillus niger, and Alternaria sp. The introduction of lactone moiety into chalcone scaffold significantly improved antimicrobial activity of the compound: γ-bromo-δ-lactone 6 and δ-hydroxy-γ-lactone 8 were significantly stronger growth inhibitors of S. aureus and F. graminearum. In the case of the latter, a clear positive effect of the lactone function on the antifungal activity was also observed for γ-bromo-δ-lactone 5.

The Role of Plasma Membrane Pleiotropic Drug Resistance Transporters in the Killer Activity of Debaryomyces hansenii and Wickerhamomyces anomalus Toxins.

The killer strains of Debaryomyces hansenii and Wickerhamomyces anomalus species secrete antimicrobial proteins called killer toxins which are active against selected fungal phytopathogens. In our research, we attempted to investigate the role of plasma membrane pleiotropic drug resistance (PDR) transporters (Pdr5p and Snq2p) in the mechanism of defense against killer toxins. Saccharomyces cerevisiae mutant strains with strengthened or weakened pleiotropic drug resistance due to increased or reduced number of mentioned PDR efflux pumps were tested for killer toxin susceptibility. The present study demonstrates the influence of the Snq2p efflux pump in immunity to W.anomalus BS91 killer toxin. It was also shown that the activity of killer toxins of D. hansenii AII4b, KI2a, MI1a and CBS767 strains is regulated by other transporters than those influencing W. anomalus killer toxin activity. In turn, this might be related to the functioning of the Pdr5p transporter and a complex cross-talk between several regulatory multidrug resistance networks. To the best of our knowledge, this is the first study that reports the involvement of PDR transporters in the cell membrane of susceptible microorganisms in resistance to killer yeasts' toxins.

Composition and Antimicrobial Activity of Ilex Leaves Water Extracts.

Plants from the Ilex genus are known for properties such as antimicrobial and anti-inflammatory activity, can act as antiobesity agents and thus can be helpful in medicine. Some holly species, such as Ilex paraguariensis (widely known in the form of popular beverage: yerba mate), have been investigated, while others have been partially researched or remain unknown. Therefore, we performed qualitative and quantitative phytochemical analyses and screened antimicrobial properties of lesser-studied species (I. aquifolium L., I. aquifolium 'Argentea Marginata' and I. × meserveae 'Blue Angel'). I. paraguariensis was used as a standard species for comparison purposes. Investigations were performed on water extracts due to their expected activity and composition. Antimicrobial research included evaluating minimal inhibitory, bactericidal (Staphylococcus aureus and Escherichia coli) and fungicidal concentration (Candida albicans, Alternaria alternata, Fusarium oxysporum, and Aspergillus niger) of extracts. The influence of the extracts on the production, eradication, and viability of bacterial biofilms was also analysed. It was established that Ilex paraguariensis possesses the richest profile of hydroxycinnamic acids derivatives in terms of component concentration and diversity. Ilex spp., especially I. × meserveae, contain a slightly higher amount of flavonoids and more different flavonoid derivatives than I. paraguariensis. However, the strongest antibacterial activity was shown by I. aquifolium L. and its cultivar 'Argentea Marginata' in terms of minimal inhibitory, bactericidal and fungicidal concentration, and biofilm assays. Extracts from both species significantly reduced the biofilm viability of S. aureus as well, which may be of use in the production of multicomponent lavaseptics, antiseptics, diuretics (supporting urinary tract infection therapy) and, due to their action on fungi, additives to growth media for specific fungi. The significant content of saponins enables Ilex extracts to be used as natural emulsifiers, for example, in cosmetics. Moreover, relatively high chlorogenic acid and rutin content may suggest use of Ilex spp. to treat obesity, digestive problems, in chemoprevention, and as preservatives in the food industry.

New Cytoplasmic Virus-Like Elements (VLEs) in the Yeast Debaryomyces hansenii.

Yeasts can have additional genetic information in the form of cytoplasmic linear dsDNA molecules called virus-like elements (VLEs). Some of them encode killer toxins. The aim of this work was to investigate the prevalence of such elements in D. hansenii killer yeast deposited in culture collections as well as in strains freshly isolated from blue cheeses. Possible benefits to the host from harboring such VLEs were analyzed. VLEs occurred frequently among fresh D. hansenii isolates (15/60 strains), as opposed to strains obtained from culture collections (0/75 strains). Eight new different systems were identified: four composed of two elements and four of three elements. Full sequences of three new VLE systems obtained by NGS revealed extremely high conservation among the largest molecules in these systems except for one ORF, probably encoding a protein resembling immunity determinant to killer toxins of VLE origin in other yeast species. ORFs that could be potentially involved in killer activity due to similarity to genes encoding proteins with domains of chitin-binding/digesting and deoxyribonuclease NucA/NucB activity, could be distinguished in smaller molecules. However, the discovered VLEs were not involved in the biocontrol of Yarrowia lipolytica and Penicillium roqueforti present in blue cheeses.

Biophysico-Chemical Properties of Alginate Oligomers Obtained by Acid and Oxidation Depolymerization.

The aim of the study was to obtain alginate oligosaccharides by using two degradation methods of sodium alginate (SA): with hydrochloric acid (G-guluronate, M-mannuronate and G + M fractions) and hydrogen peroxide (HAS-hydrolyzed SA), in order to assess and compare their biological activity and physico-chemical properties, with an attempt to produce gels from the obtained hydrolysates. The efficiency of each method was determined in order to select the fastest and most efficient process. The ferric ion reducing antioxidant power (FRAP), the ability to scavenge DPPH free radicals, rheological properties, Fourier Transformed Spectroscopy (FTIR) and the microbiological test against Escherichia coli and Staphylococcus aureus were performed. In order to check the functional properties of the obtained oligosaccharides, the texture profile analysis was assessed. The hydrolysis yield of acid SA depolymerization was 28.1% and from hydrogen peroxide SA, depolymerization was 87%. The FTIR analysis confirmed the degradation process by both tested methods in the fingerprint region. The highest ferric reducing antioxidant power was noted for HSA (34.7 µg), and the highest hydroxyl radical scavenging activity was obtained by G fraction (346 µg/Trolox ml). The complete growth inhibition (OD = 0) of alginate hydrolysates was 1%. All tested samples presented pseudoplastic behavior, only HSA presented the ability to form gel.

Enzymatic hydrolysis using bacterial cultures as a novel method for obtaining antioxidant peptides from brewers' spent grain.

Brewers' spent grain was used as a substrate to obtain protein hydrolysates with antioxidant activity. Hydrolysis was conducted in the culture using proteolytic bacteria. Hydrolysis was controlled by measurement of α-amino group concentration and with the aid of size exclusion chromatography. For each culture the degree of hydrolysis was calculated. The most efficient protein hydrolysis was observed in the cultures of Bacillus cereus (43.06%) and Bacillus lentus (41.81%). In addition, gelatin zymography was performed in order to detect bacterial proteases and their activity. The profile of secreted enzymes was heterogeneous, while the greatest variety was observed for Bacillus polymyxa. Brewers' spent grain protein hydrolysates exhibited high antioxidant activity. Bacillus subtilis and Bacillus cereus post-cultured media displayed the highest activity, respectively 1291.97 and 1621.31 µM TEAC per g for ABTS, 188.89 and 160.93 µM TEAC per g for DPPH, and 248.81 and 284.08 µM TEAC per g for the FRAP method.

Antimicrobial chloro-hydroxylactones derived from the biotransformation of bicyclic halolactones by cultures of Pleurotus ostreatus.

The aim of this research was to test the ability of cultures of edible fungi to biotransform three bicyclic halolactones. The substrates (2-chloro-, 2-bromo- and 2-iodo-4,4,6,7-tetramethyl-9-oxabicyclo[4.3.0]nonan-8-one) received by means of synthesis were transformed by oyster mushroom Pleurotus ostreatus and edible mushrooms of the genus Armillaria mellea, Marasmius scorodonius and Laetiporus sulfureus. The substrates were converted to hydroxyl derivatives only by the cultures of oyster mushroom. Out of seven strains of Pleurotus ostreatus - three were capable of hydroxylation of all substrates with the most effective conversion of chlorolactone. Bromo- and iodolactone were transformed to a small extent. Four new chloro-hydroxylactones were obtained as biotransformation products. The structures of substrates and products were established on the basis of spectroscopic data. Studies of antimicrobial activity performed on reference strains of pathogenic microorganisms showed that halolactones caused complete inhibition of growth of A. alternata and F. linii strains. On the other hand, chloro-hydroxylactones were able to completely inhibit the growth of A. alternata and F. linii strains and also C. albicans strain.

New Look on Antifungal Activity of Silver Nanoparticles (AgNPs).

The progress of research on silver nanoparticles (AgNPs) has led to their inclusion in many consumer products (chemicals, cosmetics, clothing, water filters, and medical devices) as a biocide. Despite the widespread use of AgNPs, their biocidal activity is not yet fully understood and is usually associated with various factors (size, composition, surface, red-ox potential, and concentration) and, obviously, specific features of microorganisms. There are merely a few studies concerning the interaction of molds with AgNPs. Therefore, the determination of the minimal AgNPs concentration required for effective growth suppression of five fungal species (Paecilomyces variotii, Penicillium pinophilum, Chaetomium globosum, Trichoderma virens, and Aspergillus brasiliensis), involved in the deterioration of construction materials, was particularly important. Inhibition of bacteria (Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli) and yeasts (Candida albicans and Yarrowia lipolytica) was also assessed as the control of AgNPs effectiveness. AgNPs at the concentrations of 9-10.7 ppm displayed high inhibitory activity against moulds, yeast, and bacteria. The TEM images revealed that 20 nm AgNPs migrated into bacterial, yeast, and fungal cells but aggregated in larger particles (50-100 nm) exclusively inside eukaryotic cells. The aggregation of 20 nm AgNPs and particularly their accumulation in the cell wall, observed for A. brasiliensis cells, are described here for the first time.The progress of research on silver nanoparticles (AgNPs) has led to their inclusion in many consumer products (chemicals, cosmetics, clothing, water filters, and medical devices) as a biocide. Despite the widespread use of AgNPs, their biocidal activity is not yet fully understood and is usually associated with various factors (size, composition, surface, red-ox potential, and concentration) and, obviously, specific features of microorganisms. There are merely a few studies concerning the interaction of molds with AgNPs. Therefore, the determination of the minimal AgNPs concentration required for effective growth suppression of five fungal species (Paecilomyces variotii, Penicillium pinophilum, Chaetomium globosum, Trichoderma virens, and Aspergillus brasiliensis), involved in the deterioration of construction materials, was particularly important. Inhibition of bacteria (Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli) and yeasts (Candida albicans and Yarrowia lipolytica) was also assessed as the control of AgNPs effectiveness. AgNPs at the concentrations of 9­10.7 ppm displayed high inhibitory activity against moulds, yeast, and bacteria. The TEM images revealed that 20 nm AgNPs migrated into bacterial, yeast, and fungal cells but aggregated in larger particles (50­100 nm) exclusively inside eukaryotic cells. The aggregation of 20 nm AgNPs and particularly their accumulation in the cell wall, observed for A. brasiliensis cells, are described here for the first time.

Synthesis and Biological Evaluation of Novel Aminochalcones as Potential Anticancer and Antimicrobial Agents.

A series of 18 aminochalcone derivatives were obtained in yields of 21.5-88.6% by applying the classical Claisen-Schmidt reaction. Compounds 4-9, 14 and 16-18 with 4-ethyl, 4-carboxy-, 4-benzyloxy- and 4-benzyloxy-3-methoxy groups were novel, not previously described in the scientific literature. To determine the biological properties of the synthesized compounds, anticancer and antimicrobial activity assays were performed. Antiproliferative potential was evaluated on four different human colon cancer cell lines-HT-29, LS180, LoVo and LoVo/DX -using the SRB assay and compared with green monkey kidney fibroblasts COS7. Anticancer activity was described as the IC50 value. The best results were observed for 2'-aminochalcone (1), 3'-aminochalcone (2) and 4'-aminochalcone (3) (IC50 = 1.43-1.98 µg·mL-1) against the HT-29 cell line and for amino-nitrochalcones 10-12 (IC50 = 2.77-3.42 µg·mL-1) against the LoVo and LoVo/DX cell lines. Moreover, the antimicrobial activity of all derivatives was evaluated on two strains of bacteria: Escherichia coli ATCC10536 and Staphylococcus aureus DSM799, the yeast strain Candida albicans DSM1386 and three strains of fungi: Alternaria alternata CBS1526, Fusarium linii KB-F1 and Aspergillus niger DSM1957. In the case of E. coli ATCC10536 almost all derivatives hindered the bacterial growth (∆OD = 0). Furthermore, the best results were observed in the presence of 4'-aminochalcone (3), that completely limited the growth of all tested strains at the concentration range of 0.25-0.5 mg·mL-1. The strongest bacteriostatic activity was exhibited by novel 3'-amino-4-benzyloxychalcone (14), that prevented the growth of E. coli ATCC10536 with MIC = 0.0625 mg·mL-1.

Synthesis and Antimicrobial Activity of Methoxy- Substituted γ-Oxa-ε-lactones Derived from Flavanones.

Six γ-oxa-ε-lactones, 4-phenyl-3,4-dihydro-2H-1,5-benzodioxepin-2-one (5a) and its five derivatives with methoxy groups in different positions of A and B rings (5b-f), were synthesized from corresponding flavanones. Three of the obtained lactones (5b,c,f) have not been previously described in the literature. Structures of all synthesized compounds were confirmed by complete spectroscopic analysis with the assignments of signals on 1H and 13C-NMR spectra to the corresponding atoms. In most cases, lactones 5a-f exerted an inhibitory effect on the growth of selected pathogenic bacteria (Escherichia coli, Bacillus subtilis, and Staphylococcus aureus), filamentous fungi (Fusarium graminearum, Aspergillus niger, and Alternaria sp.), and yeast (Candida albicans). The broadest spectrum of activity was observed for unsubstituted lactone 5a, which was particularly active against filamentous fungi and yeast. Lactones with methoxy groups in the 3' (5c) and 4' (5d) position of B ring were more active towards bacteria whereas lactone substituted in the 7 position of the A ring (5e) exhibited higher antifungal activity. In most cases, the introduction of lactone function increased the activity of the compound compared to its flavonoid precursors, chalcones 3a-e, and flavanones 4a-f.

Role of biocontrol yeasts Debaryomyces hansenii and Wickerhamomyces anomalus in plants' defence mechanisms against Monilinia fructicola in apple fruits.

The role of killer yeasts of the species Debaryomyces hansenii and Wickerhamomyces anomalus in biocontrol of Monilinia fructicola, and their involvement in plant defence mechanisms against brown rot in apple fruits, were investigated. D. hansenii KI2a and W. anomalus BS91 strains showed the highest in vitro biocontrol activity, inhibiting mycelium growth by 69.53% and 66.08% respectively, as compared to control fungal cultures. Brown rot on apple fruits was significantly reduced by BS91 and two strains of D. hansenii KI2a and AII4b by 92.46%, 85.10% and 70.02%, respectively, in comparison to infected fruits, which did not receive any pre-treatment. In enzymatic tests, the most significant changes in peroxidase (POD) and catalase (CAT) activities were observed in fruits inoculated either with BS91 followed by M. fructicola infection or with AII4b yeast strain alone, where POD activities were significantly higher by 67% and 54%, respectively, and CAT activities were significantly lower by 65% and 68%, respectively, than in untreated control fruits. These results confirmed the ability of killer yeasts to influence host-defence related enzyme activities in apple fruit tissue and may suggest that AII4b killer strain has a potential as biocontrol agent prior to infection by triggering immune response mechanisms in plant tissue, whereas BS91 strain is the most effective during pathogen infection and could be used as biocontrol agent in postharvest disease onset. Accordingly, the antagonistic strains of W. anomalus BS91 and D. hansenii KI2a and AII4b could be proposed as active ingredients for the development of biofungicide against M. fructicola.

Biotransformation of α-Acetylbutyrolactone in Rhodotorula Strains.

Due to its structural similarity, the α'-1'-hydroxyethyl-γ-butyrolactone obtained by reduction of (±)-α-acetyl-γ-butyrolactone may have a similar function in the body to γ-butyrolactone (GBL). In the work presented, biotransformation of α-acetyl-γ-butyrolactone by three Rhodotorula strains was performed obtaining enantiomerically enriched alcohol. The process was carried out in growing and resting cultures. We studied how both media composition and organic solvent volume affected stereoselectivity and effectiveness of biotransformation. After 2 h, the enantiomerically pure (3R, 1'S)-α'-1'-hydroxyethyl-γ-butyrolactone was obtained using the R. marina AM77 strain in YPG (Yeast extract-Peptone-Glucose) medium enriched with 5% glycerol. To our best knowledge there is no previous information in the literature about the (±)-α-acetyl-γ-butyrolactone biotransformation performed in medium with addition of organic and deep eutectic solvents.

New keratinolytic bacteria in valorization of chicken feather waste.

There is an increasing demand for cost-effective and ecologically-friendly methods for valorization of poultry feather waste, in which keratinolytic bacteria present a great potential. Feather-degrading bacteria were isolated from living poultry and a single strain, identified as Kocuria rhizophila p3-3, exhibited significant keratinolytic properties. The bacterial strain effectively degraded up to 52% of chicken feathers during 4 days of culture at 25 °C. Zymographic analysis revealed the presence of two dominating proteolytic enzymes in the culture fluid. Culture conditions were optimized in order to maximize the liberation of soluble proteins and free amino acids. A two-step procedure was used, comprising a Plackett-Burman screening design, followed by a Box-Behnken design. Concentration of feather substrate, MgSO4 and KH2PO4 were the most influential parameters for the accumulation of soluble proteins in culture K. rhizophila p3-3, while feathers and MgSO4 also affected the concentration of amino acids. The resultant raw hydrolysate supernatant, prior to and after additional treatments, was rich in phenylalanine, histidine, arginine and aspartic acid. Additionally the hydrolysate exhibited radical-scavenging activity and ferric reducing power.

Microbial transformations of 4'-methylchalcones as an efficient method of obtaining novel alcohol and dihydrochalcone derivatives with antimicrobial activity.

Biotransformations are an alternative method of receiving dihydrochalcones as a result of the reduction of α,ß-unsaturated ketones - chalcones. In presented research, two strains of bacteria - Gordonia sp. DSM44456 and Rhodococcus sp. DSM364 - were selected as effective biocatalysts that are able to transform chalcones in a short period of time. As a result of our investigation 3 new dihydrochalcones and one novel alcohol were obtained with high isolated yields. All 4'-methylchalcone derivatives and biotransformations products were tested for antimicrobial activity against Escherichia coli ATCC10536, Staphylococcus aureus DSM799, Candida albicans DSM1386, Alternaria alternata CBS1526, Fusarium linii KB-F1, and Aspergillus niger DSM1957. The best inhibitory effect was observed for all chalcones against E. coli ATCC10536 - compounds 1-6 and 8 prevented thorough growth of this strain (ΔOD = 0). Moreover, dihydrochalcones showed about 2-3 times stronger inhibitory effect against S. aureus DSM799 in comparison to their chalcones. Excluding the E. coli ATCC10536 strain, 3-(4-carboxyphenyl)-1-(4-methylphenyl)propan-1-ol (8b) had weaker biological activity than 4-carboxy-4'-methyl-α,ß-dihydrochalcone (8a).

Synthesis and Biological Activity of Novel O-Alkyl Derivatives of Naringenin and Their Oximes.

O -Alkyl derivatives of naringenin ( 1a - 10a ) were prepared from naringenin using the corresponding alkyl iodides and anhydrous potassium carbonate. The resulting products were used to obtain oximes ( 1b - 10b ). All compounds were tested for antimicrobial activity against Escherichia coli ATCC10536, Staphylococcus aureus DSM799, Candida albicans DSM1386, Alternaria alternata CBS1526, Fusarium linii KB-F1, and Aspergillus niger DSM1957. The resulting biological activity was expressed as the increase in optical density (ΔOD). The highest inhibitory effect against E. coli ATCC10536 was observed for 7,4'-di- O -pentylnaringenin ( 8a ), 7- O -dodecylnaringenin ( 9a ), naringenin oxime ( NG-OX ), 7,4'-di- O -pentylnaringenin oxime ( 8b ), and 7- O -dodecylnaringenin oxime ( 9b ) (ΔOD = 0). 7- O -dodecylnaringenin oxime ( 9b ) also inhibited the growth of S. aureus DSM799 (ΔOD = 0.35) and C. albicans DSM1386 (ΔOD = 0.22). The growth of A. alternata CBS1526 was inhibited as a result of the action of 7,4'-di- O -methylnaringenin ( 2a ), 7- O -ethylnaringenin ( 4a ), 7,4'-di- O -ethylnaringenin ( 5a ), 5,7,4'-tri- O -ethylnaringenin ( 6a ), 7,4'-di- O -pentylnaringenin ( 8a ), and 7- O -dodecylnaringenin ( 9a ) (ΔOD in the range of 0.49-0.42) in comparison to that of the control culture (ΔOD = 1.87). In the case of F. linii KB-F1, naringenin ( NG ), 7,4'-di- O -dodecylnaringenin ( 10a ), 7- O -dodecylnaringenin oxime ( 9b ), and 7,4'-di- O -dodecylnaringenin oxime ( 10b ) showed the strongest effect (ΔOD = 0). 7,4'-Di- O -pentylnaringenin ( 8a ) and naringenin oxime ( NG-OX ) hindered the growth of A. niger DSM1957 (ΔOD = 0).

Influence of structure of lactones with the methylcyclohexene and dimethylcyclohexene ring on their biotransformation and antimicrobial activity.

The aim of this article is influence of the structure of lactones with the methylcyclohexene and dimethylcyclohexene ring on their biotransformation and antimicrobial activity. This work was based on the general remark that even the smallest change in the structure of a compound can affect its biological properties. The results of the biotransformation of four bicyclic unsaturated lactones with one or two methyl groups in the cyclohexene ring was tested using fifteen fungal strains (Fusarium species, Penicillium species, Absidia species, Cunninghamella japonica, and Pleurotus ostreatus) and five yeast strains (Yarrowia lipolytica, Rhodorula marina, Rhodorula rubra, Candida viswanathii, and Saccharomyces cerevisiae). During these transformations, new epoxylactone and hydroxylactone were obtained. The relationship between the substrate structure and the ability of the microorganisms to transform them were analysed. Only compounds with C-O bond of lactone ring in the equatorial position were transformed by fungus. All presented here lactones were examined also for their antimicrobial activity. It turned out that these compounds exhibited growth inhibition of bacteria and fungi, mainly Bacillus subtilis, Candida albicans, Aspergillus niger, and Penicillium expansum.

Postharvest biocontrol ability of killer yeasts against Monilinia fructigena and Monilinia fructicola on stone fruit.

The antagonistic effects of Debaryomyces hansenii KI2a, D. hansenii MI1a and Wickerhamomyces anomalus BS91 were tested against Monilinia fructigena and Monilinia fructicola in in vitro and in vivo trials. All yeast strains demonstrated antifungal activity at different levels depending on species, strain and pathogen. D hansenii KI2a and W. anomalus BS91 showed the highest biocontrol activity in vitro; the production of hydrolytic enzymes, killer toxins and volatile organic compounds (VOCs) were hypothesized as their main mechanisms of action against pathogens. D hansenii KI2a and W. anomalus BS91 significantly reduced brown rot incidence and severity on peach and plum fruits artificially inoculated with M. fructigena and M. fructicola, especially when applied 24 h before pathogen inoculation. On the opposite, D. hansenii MI1a exhibited weak antagonistic activity towards M. fructigena on peach and plum fruits and was ineffective against M. fructicola. The noticeable ability of W. anomalus BS91 to control brown rot could be also correlated with its high capacity to colonize the wound tissue and to increase its population density. Accordingly, the antagonistic strains of D. hansenii and W. anomalus could be proposed as active ingredients for the development of biofungicides against Monilinia species that are responsible for considerable economic losses in stone fruit crops.

Biotransformation of Bicyclic Halolactones with a Methyl Group in the Cyclohexane Ring into Hydroxylactones and Their Biological Activity.

The aim of this study was the chemical synthesis of a series of halo- and unsaturated lactones, as well as their microbial transformation products. Finally some of their biological activities were assessed. Three bicyclic halolactones with a methyl group in the cyclohexane ring were obtained from the corresponding γ,δ-unsaturated ester during a two-step synthesis. These lactones were subjected to screening biotransformation using twenty two fungal strains. These strains were tested on their ability to transform halolactones into new hydroxylactones. Among the six strains able to catalyze hydrolytic dehalogenation, only two (Fusarium equiseti, AM22 and Yarrowia lipolytica, AM71) gave a product in a high yield. Moreover, one strain (Penicillium wermiculatum, AM30) introduced the hydroxy group on the cyclohexane ring without removing the halogen atom. The biological activity of five of the obtained lactones was tested. Some of these compounds exhibited growth inhibition against bacteria, yeasts and fungi and deterrent activity against peach-potato aphid.