we are treating the explant outside the LAF cabinet with running tap water, then tween20 3 drops for 10 min in running water, then 0.1% mercuric chloride for 5 min, then 0.1% cephataxim and 3 times water wash.
Then under LAF cabinet Sodium hypochlorite 5% for 10 min and sterilized water wash 3x.
but still getting excess fungal contamination.
This is totally out of my expertise, but since you are having problems and in an apparent stage of trial and error, you are seeking approaches to try. I cannot comment on your washing methods and chemical used as to their safety or why it is important to sterilize them (sale, research, medicine, etc). My comments may have some questions for you, but you dont need to answer me, they are just my way of interjecting ideas for you to consider.
But in the trial and error mode, you might try after washing, irradiating with UV light (they use that to help sterilize water in some systems) and drying with low humidity air. I assume boiling water or steam is not what you want to use as this may cook the ginger. When I go to the store, there is ginger to buy, and I do not notice a fungus, is it something that can be seen or hidden in the ginger skin. Is the fungus a health concern or does fungus produce something useful to science, medicine?
I do not know how ginger is processed here in USA, but it does not grow on wet sites, and the soil residues are minor, and brushed off like you might with mushrooms, potatoes, carrots, etc. perhaps rinsing, washing and/or pealing before use. I am not sure ginger processing here gets that level of washing and treating. Perhaps you are doing too much, making it absorb water to be saturated beyond the natural level, and as such difficult to dry sufficiently. Maybe washing and pealing is best done just before use. Interesting problem, and I do not know if there might be health or other standards that apply to your situation. I may look at ginger root in the store a little differently.
Perhaps this will help with more details used in Hawaii for washing, drying, etc.
After washing in running tap water and removing the soil and mud,allow to dry on a filter paper.Then treat with fungide solution for 10-15 minutes along with shaking .After that wash in sterile water to remove the fungicide residue and again dry in sterile filter paper.Take the samples to laminar flow the sterilize using mercuric chloride .After washing, again dry the samples in laminar flow hood .After thorough drying inoculate in media.moisture in the explant will lead to contamination. cefotaxime wash is given to remove bacterial contamination ,that can also be done if required,however drying is important after washing.
I have done some work on rhizomes such as ginger...it is not easy to get 100% clean culture. But Rekha is right about using fungicide.
You may want to try this
1. Find healthy clean young ginger.
2. Wash them using a soft brush and any dishwasher under running water, Remove all soil and dirt. Soak them in fungicide for 15-20 minutes then leave them in running water for an hour.
3. Wash them now by soaking in sodium hypochlorite 2.5% or (50% Chlorox) solution for 5 minutes and rinse again under running tap water.
4. Dry them an sterile paper and bring in to the laminar flow.
5. Now you can use either mercury chloride or hypochlorite solution and flow you sterilization technique.
If at all the fungal contamination persist ... after step two you might want to soak the rhizomes in autoclaved sugar water (2%) for about 12 hours. This is to stimulate the germination of spores and then continue with step three to eliminate them.
These have worked for me...hope it works for you.
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