Fungicidal activity of ultradisperse humic sapropel suspensions
¹ Saint Petersburg National Research University of Information Technology, Mechanics and Optics (ITMO University), Department of Food Biotechnology and Engineering, Food Biotechnology (Vegetable Stock) Research Body, 9 Lomonosova st., RU191002 Saint Petersburg, Russia
² Federal State-funded Scientific Establishment ‘All–Russia Research Institute for Food Additives’ (GBNU VNIIPD), Department of Food Microingredients Processing, 55 Liteyniy ave., RU191014 Saint Petersburg, Russia
³ Federal State-funded Scientific Establishment ‘RAS Lake Ecology Institute’ (INOZ RAN), 9 Syevasťyanova st., RU196105 Saint Petersburg, Russia
The study compared the effect of two ultradisperse humic sapropel suspensions (UDHSS), obtained in Seryodka deposit (Pskov region, Russia), on viability of Aspergillus niger in four experiments. In Experiment 1, Aspergillus niger strain L–4 conidia with titre (3.1–3.7) × 103 CFU cm–3 were suspended in 0.1 cm3, 1.0 cm3, 2.0 cm3, 3.0 cm3, or 5.0 cm3 of either UDHSS, and immediately incubated on wort agar. In Experiments 2 and 3, Aspergillus niger L–4 conidia with the same titre were suspended in and remained in contact with 0.1 cm3, 1.0 cm3, 2.0 cm3, 3.0 cm3, or 5.0 cm3 of UDHSS for 2 or 24 hours at (20.5 ± 0.5) °C (68.9 ± 0.9°F) and incubated on wort agar. The number of colonies in Petri dishes upon 24 hours and 5 days of cultivation was observed. In Experiment 4, contamination of barley grain and distillers’ dry grain (DDG) was simulated. DDG treated with 20 cm3 kg–1 of either suspension was inseminated with Aspergillus niger L–4 at (5.1–5.3) × 103 CFU cm–3, and put under standard storage conditions, changes of microflora examined at 24 hour intervals during 5 days. As a result of Experiment 1, in consideration to statistical significance, there was little fungicidal action on Aspergillus conidia. In Experiments 2 and 3, a prominent fungicidal effect was demonstrated by both sapropel suspensions. In Experiment 4, both types of suspensions exhibited a statistically significant effect on Aspergillus conidia only in samples previously remaining in contact with 3.0 or 5.0 cm3 of suspension. Amplitude of the effect proved to be dependent on both UDHSS dosage and time of contact (2 or 24 hours).