crystallisation of PBS (10X) - (Feb/05/2014 )

It doesn't sound good... either is some precipitate forming or something is living there. If you have a microscope take a look.

It never happened to me with this recipe and using borosilicate glass. There are plenty of recipes for PBS and I don''t know if you make it in Schott bottles or not. I leave it here just in case

PBS 10X    Concentration   Quantity

NaH₂PO₄               30 mM             3.5994 g

Na₂HPO₄               70 mM             9.9372 g

NaCl               1300 mM            75.972 g

dH₂O                       -                Up to 1 L

Edit: fixing table

if it's "stringy" then it's almost certainly something growing.

even though you autoclaved it, after opening the bottle you exposed it to whatever is in the air.

oh alright I get it. And about which bottle I use. I used a Schotts Bottle

We use those and they work fine. Just practice better aseptic techniques. If it is common lab reagent, make sure everyone is informed on the proper handling of the chemicals. Sounds like someone was careless pouring the solution and introduced a contaminant.

Also in the above mentioned chemicals list he hasn't mentioned KCl. I use KCl also along with NaCl, Na2HPO4 and KH2PO4. Is that a problem?

No, KCl won't be a problem. Its chemical behaviour is almost the same as NaCl