The objectives of this study were to determine the efficacy of metabolites of a Streptomyces strain AS1 on (a) spore germination, (b) mycelial growth, (c) control of mycotoxins produced by Penicillium verrucosum (ochratoxin A, OTA), Fusarium verticillioides (fumonisins, FUMs) and Aspergillus fumigatus (gliotoxin) and (d) identify the predominant metabolites involved in control. Initial screening showed that the Streptomyces AS1 strain was able to inhibit the mycelial growth of the three species at a distance, due to the release of secondary metabolites. A macroscopic screening system showed that the overall Index of Dominance against all three toxigenic fungi was inhibition at a distance. Subsequent studies showed that the metabolite mixture from the Streptomyces AS1 strain was very effective at inhibiting conidial germination of P. verrucosum, but less so against conidia of A. fumigatus and F. verticillioides. The efficacy was confirmed in studies on a conducive semi-solid YES medium in BioScreen C assays. Using the BioScreen C and the criteria of Time to Detection (TTD) at an OD = 0.1 showed good efficacy against P. verrucosum when treated with the Streptomyces AS1 extract at 0.95 and 0.99 water activity (a w) when compared to the other two species tested, indicating good efficacy. The effective dose for 50% control of growth (ED 50) at 0.95 and 0.99 a w were approx. 0.005 ng/ml and 0.15 μg/ml, respectively, with the minimum inhibitory concentration (MIC) at both a w levels requiring > 40 μg/ml. In addition, OTA production was completely inhibited by 2.5 μg/ml AS1 extract at both a w levels in the in vitro assays. Ten metabolites were identified with four of these being predominant in concentrations > 2 μg/g dry weight biomass. These were identified as valinomycin, cyclo(L-Pro-L-Tyr), cyclo(L-Pro-L-Val) and brevianamide F.

The objective was to screen and evaluate the anti-fungal activity of lactic acid bacteria (LABs) isolated from Malaysian fermented foods against two Trichophyton species. A total of 66 LAB strains were screened using dual culture assays. This showed that four LAB strains were very effective in inhibiting growth of T. rubrum but not T. interdigitale. More detailed studies with Lactobacillus plantarum strain HT-W104-B1 showed that the supernatant was mainly responsible for inhibiting the growth of T. rubrum. The minimum inhibitory concentration (MIC), inhibitory concentration, the 50% growth inhibition (IC50) and minimum fungicide concentration (MFC) were 20 mg/mL, 14 mg/mL and 30 mg/mL, respectively. A total of six metabolites were found in the supernatant, with the two major metabolites being L-lactic acid (19.1 mg/g cell dry weight (CDW)) and acetic acid (2.2 mg/g CDW). A comparative study on keratin agar media showed that the natural mixture in the supernatants predominantly contained L-lactic and acetic acid, and this significantly controlled the growth of T. rubrum. The pure two individual compounds were less effective. Potential exists for application of the natural mixture of compounds for the treatment of skin infection by T. rubrum.

The papaya leaf juice has been long practised as a traditional remedy to cure ailments due to its medicinal properties. The objective of this research is to study the effectiveness of fermented papaya leaf to inhibit the growth of pathogenic bacteria and yeast: Staphylococcus aureus, Pseudomonas aeruginosa, Propionibacterium acnes and Candida albicans. The efficacy of fermented papaya leaf against selected pathogenic microbes was evaluated using agar well diffusion assay, broth microdilution assay and time-kill test. Evidence from data collected confirmed that fermented papaya leaf supernatant showed more pronounced antibacterial and antifungal effect than papaya leaf alone. Generally, fermented papaya leaf supernatant demonstrated potent antimicrobial effect against all bacterial pathogens tested particularly P. aeruginosa followed by P. acne and S. aureus. However, it was found that fermented papaya leaf was less effective against Candida albicans. It needs 4- to 7-folds higher concentration to inhibit 50% C. albicans growth than the bacteria. The antibacterial compounds produced in the supernatant appeared to have some bactericidal effect against P. aeruginosa, P. acne and S. aureus with the minimum inhibitory concentration (MIC>99) of 16%, 50% and 60%, respectively. Particularly, the fermented papaya leaf supernatant at 60% concentration showed 100% inhibition rate within 30 mins against P. aeruginosa. However, it needs a longer time to show the same inhibition effect against S. aureus and P. acne, which was about 2-6 h. The potent killing effect of fermented papaya leaf showed a potential use in skincare application to control pathogenic microbe infection