ISHS Acta Horticulturae 819: International Symposium on Growing Media 2007
ENHANCED ANTIMICROBIAL METABOLITE FORMATION BY THE MICROFLORA INHABITING NUTRIENT SOLUTIONS IN CLOSED GROWING SYSTEMS |
| Authors: | B.W. Alsanius, V. Jung, T. Brand |
| Keywords: | 2,4-diacetyl phloroglucinol, ß-1,3-glucanase, cellulase, cellulose, cell wall degrading enzymes, cell wall preparation, chitin, chitinase, Fusarium oxysporum f.sp. cyclaminis, glucan, glucose, protease, pyoluteorin, pyrolnitrin, Pythium ultimum |
| Abstract:
Prospects for enhancing microbial metabolite formation were studied with respect to production of antimicrobial agents (2,4-diacetyl phloroglucinol, phl; pyoluteorin, plt; pyrolnitrin, prn) and to activity of enzymes degrading fungal cell walls (proteolytic, chitinolytic, cellulolytic, ß-1,3-glucanolytic) with a specific focus on nutritional factors. The experiments were conducted using the composite microflora selected from the effluent nutrient solution of a closed system with tomato. In addition, strains capable of producing antimicrobial compounds (Pf-5, 5.014) were used for the experiments on phl, plt and prn. Complex nutrient broths (yeast malt broth, King B broth, mineral nutrient broth supplemented with 2% of glycerol) were chosen as nutrient sources for improving production of antimicrobial substances. For enhanced enzyme activity, D(+)-glucose, chitin, cellulose, curdlan as well as fungal cell wall preparations of Fusarium oxysporum f.sp. cyclaminis and Pythium ultimum were selected. Production of antimicrobial compounds was verified by HPLC analysis. Enzyme activity was analyzed using dye-labelled enzyme substrates. Concentrations of 30-90, 60-90 and 0.3-0.7 µM of phl, plt and prn were found after enrichment of Pf-5 in the selected media. Most consistent in the nutrient solution among the chosen metabolites was formation of phl, resulting in concentrations around 0.1-0.2 µM. The two other metabolites could not be verified after enrichment in the nutrient solution. As expected, enrichment by the selected broth had a significant effect not only on viable counts in the nutrient solution, but also on the microbial composition. Also regarding enzyme activities, the potential of the indigenious microflora could be determined for all tested substrates and particularly high amounts of ß-1,3-glucanase were formed in the presence of 0.1% of cell wall preparations of Fusarium oxysporum f.sp. cyclaminis. | |
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