Your first problem will be to get the flavour and smell of mango chutney out of it. I've got a 120 litre one and I've tried everything: bleach, sodium bicarbonate, hot soapy water, I've even used it for a water storage tank during a concreting project and got plenty of cement in there. After all this over three years, I still haven't got the smell of garlic out of it. I use for for storing bags of barbecue charcoal now, hoping the charcoal will pick up the smell of garlic and transfer it to the food.
It would probably hold some sort of pressure bit I doubt you'll be able to seal the lid effectively. And it's a big volume of beer to waste if the seam splits.
