I want to prepare a solution of the fungicide benomyl (benlate) with a concentration about 4 mg/ml. Literature describes this product (powder) as insoluble in water. Since I am going to perform cultivation experiments with bacteria I preferably want to avoid using potentially toxic solvents such as chloroform or methanol.
My question now is whether anyone could give me advice on how to prepare a suitable solution for my purpose or has any experiences with this fungicide?
Solubility of benomyl to ethanol is 0.4 g /100 ml which means that you can make ethanol stocks with up to 40 mg/ml (10 times more that the one you need). You will be able to make a 4mg/ml concentration by applying a volume of the etthanol stock solution (40ppm) using the dilution C1V1=C2V2 clasic formula.The water insolubility limitation will not be a real problem as long as you cultivate bacteria in liquid media under continouus agitation.
Can you please tell me what exactly you are doing with the fungicide so that the toxic problems of chloroform/ methanol can be dealt with? Secondly sine you dont want to dissolve the compound in methanol due to its toxic nature so are you sure ethanol will not be toxic?
I am going to perform enrichment cultivation with algae and in order to eliminate or atleast reduce the risk of fungal contamination I chose to prepare a fungicide solution which was recommended in a publication I recently read.
I wanted to avoid chloroform/methanol since handling of the solution and further experiments would be more stressing. Ethanol has proven to only have little influence on the cultivation methods I am going to perform, since e.g. the antibiotics we use are also dissolved in ethanol and they work just fine.
Hope i could answer your questions
I have had no success with 95% benomyl in 95% EtOH. Even concentrations 10X less than its reported solubility (even tried warm water bath). I had success with acetone but the benomyl precipitates out when the stock is added to water. The only success I have had is boiling the benomyl in intended growth medium. The literature also states autoclaving will get it to dissolve.
Thank you very much. I had already distanced myself from benomyl and was trying out nystatin, which I also had trouble with in terms of solubility.
I will definetly try autoclaving the benomyl with the rest of the media additives.
Thank you very much!
Benomyl is ineffective for some fungi, such as the Basidiomycetes, and many Mucorales, making it useful in selective media for these fungi but infeffective if these will be contaminants. See references: Worrall, J.J. 1991. Media for Selective Isolation of Hymenomycetes. Mycologia. 83(3): 296-302. DOI: 10.2307/3759989. Kuhlman, E.; Hendrix Jr, F. 1962. A selective medium for the isolation of Fomes annosus. Phytopathology. S2: 1310-12.
Does anyone know how to use the Benomyl in Plant tissue culture?
As suggested by Thorn et al 1996 and confirmed by my own experience, benomyl can be easily dissolved in a 50:50 solution of acetone and 70% ethanol at a concentration of 2mg/ml. Store in darkness at 4C. 2ml of this solution in 1000ml (4ug benomyl/ml media) of liquid or solid medium is effective, but you should also consider using antibiotics, etc. appropriate for the application.
An alternative is to use the commercial fungicide that produces a suspension in water.
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