Inhibitory activity of propolis and essential oils against oomycete pathogens important in aquaculture

doctoral thesis

• Title (croatian): Inhibicijsko djelovanje propolisa i eteričnih ulja na oomicetne patogene značajne za slatkovodnu akvakultur
• Author: Anđela Miljanović
• Mentor: Ana Bielen (mentor)
• Mentor: Maja Dent (komentor)
• Committee member: Verica Dragović-Uzelac (predsjednik povjerenstva)
• Committee member: Lidija Šver (član povjerenstva)
• Committee member: Marin Ježić (član povjerenstva)
• Committee member: Tomislav Vladušić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Biochemical Engineering); (Laboratory for Biology and Microbial Genetics); Zagreb
• Defense date and country: 2022-04-14, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology
• Universal decimal classification (UDC): 663 - Industrial microbiology. Industrial mycology. Zymurgy, fermentation industry. Beverage industry. Stimulant industry

Abstract

Saprolegnia parasitica and Aphanomyces astaci are oomycete pathogens that cause significant economic losses in salmonid and crayfish aquaculture. In this dissertation, inhibition of their growth and reproduction by sage, rosemary and bay laurel essential oils and fluid propolis formulations was investigated, as environmentally friendly alternatives to the toxic chemicals currently used. Considering the high cost of essential oil production, the isolation of essential oil from bay laurel, sage and rosemary leaves was optimised to increase the yield. Ultrasonic and reflux extraction hydrodistillation pretreatments increased the essential oil yield by up to 60%, while the overall quality of the oil remained largely unchanged. In contrast, the use of cell wal degrading enzymes as hydrodistillation pretreatments did not affect the yield. Next, it was shown that the tested essential oils and propolis formulations strongly inhibited the motility and germination of zoospores and the growth of the mycelium of both pathogens, albeit with differences in efficacy depending on the substance, oomycete species and life cycle stage. The fluid propolis formulations most potently inhibited mycelial growth of A. astaci, while the sage essential oil most strongly inhibited zoospore germination and mycelium growth of S. parasitica and zoospore germination of A. astaci. Although the results point to several compounds as the basis of the inhibitory effect, such as camphor in sage and chrysin in propolis, the observed anti-oomycetic activity is probably due to the synergistic effect of many different bioactive components present at low concentrations. Overall, the results of this doctoral thesis provide a starting point for further in vivo testing of the use of essential oils and propolis formulations in freshwater aquaculture as an environmentally acceptable control of diseases caused by oomycetes.

Abstract (english)

Saprolegnia parasitica i Aphanomyces astaci su patogeni iz skupine vodenih plijesni (Oomycota) koji uzrokuju značajne ekonomske štete u akvakulturi salmonida i rakova. U ovoj disertaciji istražena je njihova inhibicija eteričnim uljima kadulje, ružmarina i lovora te tekućim pripravcima propolisa, kao ekološki prihvatljivim alternativama toksičnim kemikalijama koje se trenutno koriste. Obzirom na visoku cijenu proizvodnje eteričnih ulja, s ciljem povećanja prinosa optimizirani su uvjeti izolacije eteričnog ulja iz listova kadulje, lovora i ružmarina. Predtretmani ultrazvukom i klasičnom ekstrakcijom uz refluks povećali su prinos eteričnog ulja do 60 %, pri čemu je kvaliteta eteričnog ulja ostala uglavnom nepromijenjena. Nasuprot tomu, primjena enzima koji razgrađuju staničnu stijenku kao predtretman hidrodestilaciji nije povećala prinos ulja. Nadalje, pokazano je da su testirani uzorci eteričnih ulja i propolisa snažno inhibirali pokretljivost i klijavost zoospora i rast micelija oba patogena, ali s razlikama u djelotvornosti ovisno o uzorku, vrsti patogena te fazi životnog ciklusa. Tekuće formulacije propolisa najsnažnije su inhibirale rast micelija vrste A. astaci, dok je eterično ulje kadulje najjače inhibiralo klijavost zoospora i rast micelija vrste S. parasitica te zoospore vrste A. astaci. Iako rezultati ukazuju na nekoliko komponenti kao osnovu inhibicijskog učinka, primjerice kamfor u kadulji i krizin u propolisu, demonstrirano inhibicijsko djelovanje je vjerojatno posljedica sinergističkog učinka većeg broja različitih bioaktivnih komponenti prisutnih u niskim koncentracijama. Zaključno, rezultati ovog doktorskog rada predstavljaju polazište za daljnja in vivo istraživanja primjene eteričnih ulja i propolisa u slatkovodnoj akvakulturi u svrhu ekološki prihvatljive kontrole bolesti uzrokovanih vodenim plijesnima.

• Keywords: Aphanomyces astaci; Saprolegnia parasitica; bay laurel; rosemary; sage; fluid propolis formulations
• Keywords (english): Aphanomyces astaci; Saprolegnia parasitica; lovor; ružmarin; kadulja; tekući pripravci propolisa
• Language: english
• URN:NBN: urn:nbn:hr:159:175344
• Promotion: 2022
• Study programme: Title: Postgraduate PhD Study in Nutrition; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje biotehničkih znanosti, polje nutricionizam (doktor/doktorica znanosti, područje biotehničkih znanosti, polje nutricionizam)
• Type of resource: Text
• Extent: 118 str ; 30 cm
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-11-08 10:59:29