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Novel Antifungal Peptides Produced by Leuconostoc mesenteroides DU15 Effectively Inhibit Growth of Aspergillus niger

Muhialdin BJ, Hassan Z, Abu Bakar F, Algboory HL, Saari N

J Food Sci, 2015 May;80(5):M1026-30.
PMID: 25847317 DOI: 10.1111/1750-3841.12844

The ability of Leuconostoc mesenteroides DU15 to produce antifungal peptides that inhibit growth of Aspergillus niger was evaluated under optimum growth conditions of 30 °C for 48 h. The cell-free supernatant showed inhibitory activity against A. niger. Five novel peptides were isolated with the sequences GPFPL, YVPLF, LLHGVPLP, GPFPLEMTLGPT, and TVYPFPGPL as identified by de novo sequencing using PEAKS 6 software. Peptide LLHGVPLP was the only positively charged (cationic peptides) and peptide GPFPLEMTLGPT negatively charged (anionic), whereas the rest are neutral. The identified peptides had high hydrophobicity ratio and low molecular weights with amino acids sequences ranging from 5 to 12 residues. The mode of action of these peptides is observed under the scanning electron microscope and is due to cell lysis of fungi. This work reveals the potential of peptides from L. mesenteroides DU15 as natural antifungal preservatives in inhibiting the growth of A. niger that is implicated to the spoilage during storage.

Matched MeSH terms: Antifungal Agents/metabolism
Fulltext Enhanced Natamycin production by Streptomyces natalensis in shake-flasks and stirred tank bioreactor under batch and fed-batch conditions

Elsayed EA, Farid MA, El-Enshasy HA

BMC Biotechnol, 2019 07 16;19(1):46.
PMID: 31311527 DOI: 10.1186/s12896-019-0546-2

BACKGROUND: Natamycin is an antifungal polyene macrolide antibiotic with wide applications in health and food industries. Currently, it is the only antifungal food additive with the GRAS status (Generally Regarded as Safe).
RESULTS: Natamycin production was investigated under the effect of different initial glucose concentrations. Maximal antibiotic production (1.58 ± 0.032 g/L) was achieved at 20 g/L glucose. Under glucose limitation, natamycin production was retarded and the produced antibiotic was degraded. Higher glucose concentrations resulted in carbon catabolite repression. Secondly, intermittent feeding of glucose improved natamycin production due to overcoming glucose catabolite regulation, and moreover it was superior to glucose-beef mixture feeding, which overcomes catabolite regulation, but increased cell growth on the expense of natamycin production. Finally, the process was optimized in 7.5 L stirred tank bioreactor under batch and fed-batch conditions. Continuous glucose feeding for 30 h increased volumetric natamycin production by about 1.6- and 1.72-folds in than the batch cultivation in bioreactor and shake-flasks, respectively.
CONCLUSIONS: Glucose is a crucial substrate that significantly affects the production of natamycin, and its slow feeding is recommended to alleviate the effects of carbon catabolite regulation as well as to prevent product degradation under carbon source limitation. Cultivation in bioreactor under glucose feeding increased maximal volumetric enzyme production by about 72% from the initial starting conditions.

Matched MeSH terms: Antifungal Agents/metabolism
Enhancement of anti-candidal activity of endophytic fungus Phomopsis sp. ED2, isolated from Orthosiphon stamineus Benth, by incorporation of host plant extract in culture medium

Yenn TW, Lee CC, Ibrahim D, Zakaria L

J Microbiol, 2012 Aug;50(4):581-5.
PMID: 22923105 DOI: 10.1007/s12275-012-2083-8

This study examined the effect of host extract in the culture medium on anti-candidal activity of Phomopsis sp. ED2, previously isolated from the medicinal herb Orthosiphon stamineus Benth. Interestingly, upon addition of aqueous host extract to the culture medium, the ethyl acetate extract prepared from fermentative broth exhibited moderate anti-candidal activity in a disc diffusion assay. The minimal inhibitory concentration of this extract was 62.5 μg/ml and it only exhibited fungistatic activity against C. albicans. In the time-kill study, a 50% growth reduction of C. albicans was observed at 31.4 h for extract from the culture incorporating host extract. In the bioautography assay, only one single spot (Rf 0.59) developed from the extract exhibited anti-candidal activity. A spot with the a similar Rf was not detected for the crude extract from YES broth without host extract. This indicated that the terpenoid anti-candidal compound was only produced when the host extract was introduced into the medium. The study concluded that the incorporation of aqueous extract of the host plant into the culture medium significantly enhanced the anti-candidal activity of Phomopsis sp. ED2.

Matched MeSH terms: Antifungal Agents/metabolism*
Antagonistic effects of Streptomyces violaceusniger strain G10 on Fusarium oxysporum f.sp. cubense race 4: indirect evidence for the role of antibiosis in the antagonistic process

Getha K, Vikineswary S

J Ind Microbiol Biotechnol, 2002 Jun;28(6):303-10.
PMID: 12032802

Fusarium oxysporum f.sp. cubense is the causal pathogen of wilt disease of banana. A cost-effective measure of control for this disease is still not available. Streptomyces violaceusniger strain G10 acts as an antifungal agent antagonistic towards many different phytopathogenic fungi, including different pathogenic races of the Fusarium wilt pathogen. In an attempt to understand the mode of action of this antagonist in nature, the interaction between S. violaceusniger strain G10 and F. oxysporum f.sp. cubense was first studied by paired incubation on agar plates. Evidence for the in vitro antibiosis of strain G10 was demonstrated by inhibition zones in the "cross-plug" assay plates. Microscopic observations showed lysis of hyphal ends in the inhibited fungal colonies. Culture of strain G10 in liquid media produces antifungal metabolites, which showed in vitro antagonistic effects against F. oxysporum f.sp. cubense such as swelling, distortion and excessive branching of hyphae, and inhibition of spore germination. An indirect method was used to show that antibiosis is one of the mechanisms of antagonism by which strain G10 acts against F. oxysporun f.sp. cubense in soil. This study suggests the potential of developing strain G10 for the biological control of Fusarium wilt disease of banana.

Matched MeSH terms: Antifungal Agents/metabolism
Fulltext Anti-Candida activity and biofilm inhibitory effects of secreted products of tropical environmental yeasts

Tan HW, Tay ST

Trop Biomed, 2011 Apr;28(1):175-80.
PMID: 21602784

This study describes the killer phenotypes of tropical environmental yeasts and the inhibition effects of the culture filtrates on the biofilm of Candida albicans. A total of 26 (10.5%) of 258 yeast isolates obtained from an environmental sampling study demonstrated killer activity to Candida species. The killer yeasts were identified as species belonging to the genus Aureobasidium, Pseudozyma, Ustilago and Candida based on sequence analysis of the ITS1-5.8S-ITS2 region of the yeasts. Pseudozyma showed the broadest killing effects against sensitive strains of Candida. New species of Ustilago and Pseudozyma demonstrating killer phenotypes were identified in this study. Interestingly, more than 50% reduction in the metabolic activity of Candida albicans biofilm was noted after exposure to the culture filtrates of the nine killer yeasts. Purification and characterization of toxin and metabolites are essential for understanding the yeast killing effects.

Matched MeSH terms: Antifungal Agents/metabolism*
In vitro assessment of non-irritant microemulsified voriconazole hydrogel system

Raju Y P, N H, Chowdary V H, Nair RS, Basha D J, N T

Artif Cells Nanomed Biotechnol, 2017 Dec;45(8):1539-1547.
PMID: 27887040 DOI: 10.1080/21691401.2016.1260579

Research was aimed on microemulsion-based hydrogel for voriconazole. Oleic acid and isopropyl myristate as lipid phases; tween 20: tween 80 as surfactants and PEG600 as cosurfactant were selected to formulate voriconazole microemulsions. The promising microemulsions in terms of zeta potential, pH, viscosity, and drug release were selected and developed into hydrogels using carbopol 934. Resulting microemulsion-based hydrogel (MBH) of voriconazole were evaluated for in vitro diffusion and ex vivo permeation. Antifungal potentials of MBH were assessed against selected fungal strains. Optimal MBH formulations, O6 and O8 had displayed their antifungal potentials with enlarged zone of inhibition against selected fungal strains.

Matched MeSH terms: Antifungal Agents/metabolism
Pleurotus sajor-caju can be used to synthesize silver nanoparticles with antifungal activity against Candida albicans

Musa SF, Yeat TS, Kamal LZM, Tabana YM, Ahmed MA, El Ouweini A, et al.

J Sci Food Agric, 2018 Feb;98(3):1197-1207.
PMID: 28746729 DOI: 10.1002/jsfa.8573

BACKGROUND: Green synthesis of silver nanoparticles (AgNPs) has become widely practiced worldwide. In this study, AgNPs were synthesized using a hot-water extract of the edible mushroom Pleurotus sajor-caju. The product, PSC-AgNPs, was characterized by using UV-visible spectra, dynamic light scattering analysis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectrometry. To assess its antifungal activity against Candida albicans, gene transcription and protein expression analyses were conducted for CaICL1 and its product, ICL, using real-time quantitative polymerase chain reaction and western blot, respectively.
RESULTS: PSC-AgNPs with an average particle size of 11.68 nm inhibited the growth of the pathogenic yeast C. albicans. Values for minimum inhibitory concentration and minimum fungicidal concentration were 250 and 500 mg L-1 , respectively. TEM images revealed that the average particle size of PSC-AgNPs was 16.8 nm, with the values for zeta potential and the polydispersity index being -8.54 mV and 0.137, respectively. XRD and FTIR spectra showed PSC-AgNPs to have a face-centered cubic crystalline structure. The polysaccharides and amino acid residues present in P. sajor-caju extract were found to be involved in reducing Ag+ to AgNP. Both CaICL1 transcription and ICL protein expression were found to be suppressed in the cells treated with PSC-AgNPs as compared with the control.
CONCLUSION: Our PSC-AgNP preparation makes for a promising antifungal agent that can downregulate isocitrate lyase. © 2017 Society of Chemical Industry.

Matched MeSH terms: Antifungal Agents/metabolism*
Fulltext Endophytic Diaporthe sp. ED2 Produces a Novel Anti-Candidal Ketone Derivative

Tong WY, Leong CR, Tan WN, Khairuddean M, Zakaria L, Ibrahim D

J Microbiol Biotechnol, 2017 Jun 28;27(6):1065-1070.
PMID: 28297749 DOI: 10.4014/jmb.1612.12009

This study aimed to examine the anti-candidal efficacy of a novel ketone derivative isolated from Diaporthe sp. ED2, an endophytic fungus residing in medicinal herb Orthosiphon stamieus Benth. The ethyl acetate extract of the fungal culture was separated by open column and reverse phase high-performance liquid chromatography (HPLC). The eluent at retention time 5.64 min in the HPLC system was the only compound that exhibited anti-candidal activity on Kirby-Bauer assay. The structure of the compound was also elucidated by nuclear magnetic resonance and spectroscopy techniques. The purified anti-candidal compound was obtainedas a colorless solid and characterized as 3-hydroxy-5-methoxyhex-5-ene-2,4-dione. On broth microdilution assay, the compound also exhibited fungicidal activity on a clinical strain of Candida albicans at a minimal inhibitory concentration of 3.1 μg/ml. The killing kinetic analysis also revealed that the compound was fungicidal against C. albicans in a concentration- and time-dependent manner. The compound was heat-stable up to 70°C, but its anti-candidal activity was affected at pH 2.

Matched MeSH terms: Antifungal Agents/metabolism
An in vitro study of the antifungal activity of Trichoderma virens 7b and a profile of its non-polar antifungal components released against Ganoderma boninense

Angel LP, Yusof MT, Ismail IS, Ping BT, Mohamed Azni IN, Kamarudin NH, et al.

J Microbiol, 2016 Nov;54(11):732-744.
PMID: 27796927

Ganoderma boninense is the causal agent of a devastating disease affecting oil palm in Southeast Asian countries. Basal stem rot (BSR) disease slowly rots the base of palms, which radically reduces productive lifespan of this lucrative crop. Previous reports have indicated the successful use of Trichoderma as biological control agent (BCA) against G. boninense and isolate T. virens 7b was selected based on its initial screening. This study attempts to decipher the mechanisms responsible for the inhibition of G. boninense by identifying and characterizing the chemical compounds as well as the physical mechanisms by T. virens 7b. Hexane extract of the isolate gave 62.60% ± 6.41 inhibition against G. boninense and observation under scanning electron microscope (SEM) detected severe mycelial deformation of the pathogen at the region of inhibition. Similar mycelia deformation of G. boninense was observed with a fungicide treatment, Benlate(®) indicating comparable fungicidal effect by T. virens 7b. Fraction 4 and 5 of hexane active fractions through preparative thin layer chromatography (P-TLC) was identified giving the best inhibition of the pathogen. These fractions comprised of ketones, alcohols, aldehydes, lactones, sesquiterpenes, monoterpenes, sulphides, and free fatty acids profiled through gas chromatography mass spectrometry detector (GC/MSD). A novel antifungal compound discovery of phenylethyl alcohol (PEA) by T. virens 7b is reported through this study. T. virens 7b also proved to be an active siderophore producer through chrome azurol S (CAS) agar assay. The study demonstrated the possible mechanisms involved and responsible in the successful inhibition of G. boninense.

Matched MeSH terms: Antifungal Agents/metabolism