I transferred 45 ml of DEPC water from glass bottle stock to 50 ml plastic tube. Recently i see some fungal colony in the 50ml plastic tube, but no fungi on the glass bottle. What might be the possible cause to grow fungus there??
Bacterial and fungal contamination of water is not uncommon and here you have a little substrate (ethanol) - e.g. https://academic.oup.com/cid/article/33/11/1871/445317. Apparently you contaminated upon transfer.
Fungi spores most often transmitted with air and sometime takes place in the washed lab equipment/ supporting (glass bottle, measuring cylinder etc.). During transfer these can contaminate the cultures. Moreover the low temperature sometime promote the growth of certain species of fungus. Better to use sterile glassware to avoid contamination.