stry67 wrote:Tho I find your 2.75g/L suspect. I did a batch today at 4g/L and it's just too soft.
stry67:
2.75 g/l is plenty of Gellan Gum. I am using the same G434 that you are using and I started out using 3g/l and it was a little too firm. I also use Phytagel, which is a Gellan Gum sold by Sigma and the results were the same. If you are requiring more than 3g/l with 1/2 MS media,then there is something else wrong with your technique. Possibilities are:
1. Your pH adjustment is wrong.
2. Your method of media preparation is wrong. I add the gelling agent last and always heat the media to the boiling point for a minute or two to make sure the gelling agent is completely dissolved. It will go from cloudy to clear when the gelling agent is completely in solution. Then the media can be dispensed into the vials and sterilized, or it can be sterilized in a media bottle and then dispensed into sterilized vials before it cools. Either way I swirl the vials to completely mix the gelling agent before it cools to the gelling point.
Brad